Updated direct IO optimization patchkit v3

index 44a360c..02943e3 100644
@@ -55,13 +55,10 @@
  * blocksize.
  */
 
-struct dio {
-	/* BIO submission state */
+/* dio_state only used in the submission path */
+
+struct dio_submit {
 	struct bio *bio;		/* bio under assembly */
-	struct inode *inode;
-	int rw;
-	loff_t i_size;			/* i_size when submitted */
-	int flags;			/* doesn't change */
 	unsigned blkbits;		/* doesn't change */
 	unsigned blkfactor;		/* When we're using an alignment which
 					   is finer than the filesystem's soft

@@ -71,7 +68,7 @@ struct dio {
 	unsigned start_zero_done;	/* flag: sub-blocksize zeroing has
 					   been performed at the start of a
 					   write */
-	int pages_in_io;		/* approximate total IO pages */
+	int pages_in_io;		/* approximate total IO pages */	
 	size_t	size;			/* total request size (doesn't change)*/
 	sector_t block_in_file;		/* Current offset into the underlying
 					   file in dio_block units. */

@@ -81,14 +78,13 @@ struct dio {
 	int boundary;			/* prev block is at a boundary */
 	int reap_counter;		/* rate limit reaping */
 	get_block_t *get_block;		/* block mapping function */
-	dio_iodone_t *end_io;		/* IO completion function */
-	dio_submit_t *submit_io;	/* IO submition function */
+	dio_submit_t *submit_io;	/* IO submition function */	
+
 	loff_t logical_offset_in_bio;	/* current first logical block in bio */
 	sector_t final_block_in_bio;	/* current final block in bio + 1 */
 	sector_t next_block_for_io;	/* next block to be put under IO,
 					   in dio_blocks units */
-	struct buffer_head map_bh;	/* last get_block() result */
-
+	
 	/*
 	 * Deferred addition of a page to the dio.  These variables are
 	 * private to dio_send_cur_page(), submit_page_section() and

@@ -100,18 +96,6 @@ struct dio {
 	sector_t cur_page_block;	/* Where it starts */
 	loff_t cur_page_fs_offset;	/* Offset in file */
 
-	/* BIO completion state */
-	spinlock_t bio_lock;		/* protects BIO fields below */
-	unsigned long refcount;		/* direct_io_worker() and bios */
-	struct bio *bio_list;		/* singly linked via bi_private */
-	struct task_struct *waiter;	/* waiting task (NULL if none) */
-
-	/* AIO related stuff */
-	struct kiocb *iocb;		/* kiocb */
-	int is_async;			/* is IO async ? */
-	int io_error;			/* IO error in completion path */
-	ssize_t result;                 /* IO result */
-
 	/*
 	 * Page fetching state. These variables belong to dio_refill_pages().
 	 */

@@ -125,6 +109,30 @@ struct dio {
 	 */
 	unsigned head;			/* next page to process */
 	unsigned tail;			/* last valid page + 1 */
+};
+
+/* dio_state communicated between submission path and end_io */
+struct dio {
+	int flags;			/* doesn't change */
+	struct inode *inode;
+	int rw;
+	loff_t i_size;			/* i_size when submitted */
+	dio_iodone_t *end_io;		/* IO completion function */
+	struct buffer_head map_bh;	/* last get_block() result */
+
+
+	/* BIO completion state */
+	spinlock_t bio_lock;		/* protects BIO fields below */
+	unsigned long refcount;		/* direct_io_worker() and bios */
+	struct bio *bio_list;		/* singly linked via bi_private */
+	struct task_struct *waiter;	/* waiting task (NULL if none) */
+
+	/* AIO related stuff */
+	struct kiocb *iocb;		/* kiocb */
+	int is_async;			/* is IO async ? */
+	int io_error;			/* IO error in completion path */
+	ssize_t result;                 /* IO result */
+
 	int page_errors;		/* errno from get_user_pages() */
 
 	/*

@@ -132,7 +140,7 @@ struct dio {
 	 * allocation time.  Don't add new fields after pages[] unless you
 	 * wish that they not be zeroed.
 	 */
-	struct page *pages[DIO_PAGES];	/* page buffer */
+	struct page *pages[DIO_PAGES];	/* page buffer */	
 };
 
 static void __inode_dio_wait(struct inode *inode)

@@ -182,27 +190,27 @@ EXPORT_SYMBOL_GPL(inode_dio_done);
 /*
  * How many pages are in the queue?
  */
-static inline unsigned dio_pages_present(struct dio *dio)
+static inline unsigned dio_pages_present(struct dio *dio, struct dio_submit *sdio)
 {
-	return dio->tail - dio->head;
+	return sdio->tail - sdio->head;
 }
 
 /*
  * Go grab and pin some userspace pages.   Typically we'll get 64 at a time.
  */
-static int dio_refill_pages(struct dio *dio)
+static int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret;
 	int nr_pages;
 
-	nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES);
+	nr_pages = min(sdio->total_pages - sdio->curr_page, DIO_PAGES);
 	ret = get_user_pages_fast(
-		dio->curr_user_address,		/* Where from? */
+		sdio->curr_user_address,		/* Where from? */
 		nr_pages,			/* How many pages? */
 		dio->rw == READ,		/* Write to memory? */
 		&dio->pages[0]);		/* Put results here */
 
-	if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) {
+	if (ret < 0 && sdio->blocks_available && (dio->rw & WRITE)) {
 		struct page *page = ZERO_PAGE(0);
 		/*
 		 * A memory fault, but the filesystem has some outstanding

@@ -213,17 +221,17 @@ static int dio_refill_pages(struct dio *dio)
 			dio->page_errors = ret;
 		page_cache_get(page);
 		dio->pages[0] = page;
-		dio->head = 0;
-		dio->tail = 1;
+		sdio->head = 0;
+		sdio->tail = 1;
 		ret = 0;
 		goto out;
 	}
 
 	if (ret >= 0) {
-		dio->curr_user_address += ret * PAGE_SIZE;
-		dio->curr_page += ret;
-		dio->head = 0;
-		dio->tail = ret;
+		sdio->curr_user_address += ret * PAGE_SIZE;
+		sdio->curr_page += ret;
+		sdio->head = 0;
+		sdio->tail = ret;
 		ret = 0;
 	}
 out:

@@ -236,17 +244,17 @@ out:
  * decent number of pages, less frequently.  To provide nicer use of the
  * L1 cache.
  */
-static struct page *dio_get_page(struct dio *dio)
+static struct page *dio_get_page(struct dio *dio, struct dio_submit *sdio)
 {
-	if (dio_pages_present(dio) == 0) {
+	if (dio_pages_present(dio, sdio) == 0) {
 		int ret;
 
-		ret = dio_refill_pages(dio);
+		ret = dio_refill_pages(dio, sdio);
 		if (ret)
 			return ERR_PTR(ret);
-		BUG_ON(dio_pages_present(dio) == 0);
+		BUG_ON(dio_pages_present(dio, sdio) == 0);
 	}
-	return dio->pages[dio->head++];
+	return dio->pages[sdio->head++];
 }
 
 /**

@@ -368,8 +376,9 @@ void dio_end_io(struct bio *bio, int error)
 EXPORT_SYMBOL_GPL(dio_end_io);
 
 static void
-dio_bio_alloc(struct dio *dio, struct block_device *bdev,
-		sector_t first_sector, int nr_vecs)
+dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
+	      struct block_device *bdev,
+	      sector_t first_sector, int nr_vecs)
 {
 	struct bio *bio;
 

@@ -386,8 +395,8 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev,
 	else
 		bio->bi_end_io = dio_bio_end_io;
 
-	dio->bio = bio;
-	dio->logical_offset_in_bio = dio->cur_page_fs_offset;
+	sdio->bio = bio;
+	sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
 }
 
 /*

@@ -397,9 +406,9 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev,
  *
  * bios hold a dio reference between submit_bio and ->end_io.
  */
-static void dio_bio_submit(struct dio *dio)
+static void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
 {
-	struct bio *bio = dio->bio;
+	struct bio *bio = sdio->bio;
 	unsigned long flags;
 
 	bio->bi_private = dio;

@@ -411,24 +420,24 @@ static void dio_bio_submit(struct dio *dio)
 	if (dio->is_async && dio->rw == READ)
 		bio_set_pages_dirty(bio);
 
-	if (dio->submit_io)
-		dio->submit_io(dio->rw, bio, dio->inode,
-			       dio->logical_offset_in_bio);
+	if (sdio->submit_io)
+		sdio->submit_io(dio->rw, bio, dio->inode,
+			       sdio->logical_offset_in_bio);
 	else
 		submit_bio(dio->rw, bio);
 
-	dio->bio = NULL;
-	dio->boundary = 0;
-	dio->logical_offset_in_bio = 0;
+	sdio->bio = NULL;
+	sdio->boundary = 0;
+	sdio->logical_offset_in_bio = 0;
 }
 
 /*
  * Release any resources in case of a failure
  */
-static void dio_cleanup(struct dio *dio)
+static void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
 {
-	while (dio_pages_present(dio))
-		page_cache_release(dio_get_page(dio));
+	while (dio_pages_present(dio, sdio))
+		page_cache_release(dio_get_page(dio, sdio));
 }
 
 /*

@@ -518,11 +527,11 @@ static void dio_await_completion(struct dio *dio)
  *
  * This also helps to limit the peak amount of pinned userspace memory.
  */
-static int dio_bio_reap(struct dio *dio)
+static int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret = 0;
 
-	if (dio->reap_counter++ >= 64) {
+	if (sdio->reap_counter++ >= 64) {
 		while (dio->bio_list) {
 			unsigned long flags;
 			struct bio *bio;

@@ -536,14 +545,14 @@ static int dio_bio_reap(struct dio *dio)
 			if (ret == 0)
 				ret = ret2;
 		}
-		dio->reap_counter = 0;
+		sdio->reap_counter = 0;
 	}
 	return ret;
 }
 
 /*
  * Call into the fs to map some more disk blocks.  We record the current number
- * of available blocks at dio->blocks_available.  These are in units of the
+ * of available blocks at sdio->blocks_available.  These are in units of the
  * fs blocksize, (1 << inode->i_blkbits).
  *
  * The fs is allowed to map lots of blocks at once.  If it wants to do that,

@@ -564,7 +573,7 @@ static int dio_bio_reap(struct dio *dio)
  * buffer_mapped().  However the direct-io code will only process holes one
  * block at a time - it will repeatedly call get_block() as it walks the hole.
  */
-static int get_more_blocks(struct dio *dio)
+static int get_more_blocks(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret;
 	struct buffer_head *map_bh = &dio->map_bh;

@@ -580,11 +589,11 @@ static int get_more_blocks(struct dio *dio)
 	 */
 	ret = dio->page_errors;
 	if (ret == 0) {
-		BUG_ON(dio->block_in_file >= dio->final_block_in_request);
-		fs_startblk = dio->block_in_file >> dio->blkfactor;
-		dio_count = dio->final_block_in_request - dio->block_in_file;
-		fs_count = dio_count >> dio->blkfactor;
-		blkmask = (1 << dio->blkfactor) - 1;
+		BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
+		fs_startblk = sdio->block_in_file >> sdio->blkfactor;
+		dio_count = sdio->final_block_in_request - sdio->block_in_file;
+		fs_count = dio_count >> sdio->blkfactor;
+		blkmask = (1 << sdio->blkfactor) - 1;
 		if (dio_count & blkmask)	
 			fs_count++;
 

@@ -604,12 +613,12 @@ static int get_more_blocks(struct dio *dio)
 		 */
 		create = dio->rw & WRITE;
 		if (dio->flags & DIO_SKIP_HOLES) {
-			if (dio->block_in_file < (i_size_read(dio->inode) >>
-							dio->blkbits))
+			if (sdio->block_in_file < (i_size_read(dio->inode) >>
+							sdio->blkbits))
 				create = 0;
 		}
 
-		ret = (*dio->get_block)(dio->inode, fs_startblk,
+		ret = (*sdio->get_block)(dio->inode, fs_startblk,
 						map_bh, create);
 	}
 	return ret;

@@ -618,20 +627,21 @@ static int get_more_blocks(struct dio *dio)
 /*
  * There is no bio.  Make one now.
  */
-static int dio_new_bio(struct dio *dio, sector_t start_sector)
+static int dio_new_bio(struct dio *dio, struct dio_submit *sdio, 
+		       sector_t start_sector)
 {
 	sector_t sector;
 	int ret, nr_pages;
 
-	ret = dio_bio_reap(dio);
+	ret = dio_bio_reap(dio, sdio);
 	if (ret)
 		goto out;
-	sector = start_sector << (dio->blkbits - 9);
-	nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
+	sector = start_sector << (sdio->blkbits - 9);
+	nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
 	nr_pages = min(nr_pages, BIO_MAX_PAGES);
 	BUG_ON(nr_pages <= 0);
-	dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages);
-	dio->boundary = 0;
+	dio_bio_alloc(dio, sdio, dio->map_bh.b_bdev, sector, nr_pages);
+	sdio->boundary = 0;
 out:
 	return ret;
 }

@@ -643,21 +653,21 @@ out:
  *
  * Return zero on success.  Non-zero means the caller needs to start a new BIO.
  */
-static int dio_bio_add_page(struct dio *dio)
+static int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret;
 
-	ret = bio_add_page(dio->bio, dio->cur_page,
-			dio->cur_page_len, dio->cur_page_offset);
-	if (ret == dio->cur_page_len) {
+	ret = bio_add_page(sdio->bio, sdio->cur_page,
+			sdio->cur_page_len, sdio->cur_page_offset);
+	if (ret == sdio->cur_page_len) {
 		/*
 		 * Decrement count only, if we are done with this page
 		 */
-		if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE)
-			dio->pages_in_io--;
-		page_cache_get(dio->cur_page);
-		dio->final_block_in_bio = dio->cur_page_block +
-			(dio->cur_page_len >> dio->blkbits);
+		if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
+			sdio->pages_in_io--;
+		page_cache_get(sdio->cur_page);
+		sdio->final_block_in_bio = sdio->cur_page_block +
+			(sdio->cur_page_len >> sdio->blkbits);
 		ret = 0;
 	} else {
 		ret = 1;

@@ -675,14 +685,14 @@ static int dio_bio_add_page(struct dio *dio)
  * The caller of this function is responsible for removing cur_page from the
  * dio, and for dropping the refcount which came from that presence.
  */
-static int dio_send_cur_page(struct dio *dio)
+static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret = 0;
 
-	if (dio->bio) {
-		loff_t cur_offset = dio->cur_page_fs_offset;
-		loff_t bio_next_offset = dio->logical_offset_in_bio +
-			dio->bio->bi_size;
+	if (sdio->bio) {
+		loff_t cur_offset = sdio->cur_page_fs_offset;
+		loff_t bio_next_offset = sdio->logical_offset_in_bio +
+			sdio->bio->bi_size;
 
 		/*
 		 * See whether this new request is contiguous with the old.

@@ -698,28 +708,28 @@ static int dio_send_cur_page(struct dio *dio)
 		 * be the next logical offset in the bio, submit the bio we
 		 * have.
 		 */
-		if (dio->final_block_in_bio != dio->cur_page_block ||
+		if (sdio->final_block_in_bio != sdio->cur_page_block ||
 		    cur_offset != bio_next_offset)
-			dio_bio_submit(dio);
+			dio_bio_submit(dio, sdio);
 		/*
 		 * Submit now if the underlying fs is about to perform a
 		 * metadata read
 		 */
-		else if (dio->boundary)
-			dio_bio_submit(dio);
+		else if (sdio->boundary)
+			dio_bio_submit(dio, sdio);
 	}
 
-	if (dio->bio == NULL) {
-		ret = dio_new_bio(dio, dio->cur_page_block);
+	if (sdio->bio == NULL) {
+		ret = dio_new_bio(dio, sdio, sdio->cur_page_block);
 		if (ret)
 			goto out;
 	}
 
-	if (dio_bio_add_page(dio) != 0) {
-		dio_bio_submit(dio);
-		ret = dio_new_bio(dio, dio->cur_page_block);
+	if (dio_bio_add_page(dio, sdio) != 0) {
+		dio_bio_submit(dio, sdio);
+		ret = dio_new_bio(dio, sdio, sdio->cur_page_block);
 		if (ret == 0) {
-			ret = dio_bio_add_page(dio);
+			ret = dio_bio_add_page(dio, sdio);
 			BUG_ON(ret != 0);
 		}
 	}

@@ -745,7 +755,7 @@ out:
  * page to the dio instead.
  */
 static int
-submit_page_section(struct dio *dio, struct page *page,
+submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
 		unsigned offset, unsigned len, sector_t blocknr)
 {
 	int ret = 0;

@@ -760,20 +770,20 @@ submit_page_section(struct dio *dio, struct page *page,
 	/*
 	 * Can we just grow the current page's presence in the dio?
 	 */
-	if (	(dio->cur_page == page) &&
-		(dio->cur_page_offset + dio->cur_page_len == offset) &&
-		(dio->cur_page_block +
-			(dio->cur_page_len >> dio->blkbits) == blocknr)) {
-		dio->cur_page_len += len;
+	if (	(sdio->cur_page == page) &&
+		(sdio->cur_page_offset + sdio->cur_page_len == offset) &&
+		(sdio->cur_page_block +
+			(sdio->cur_page_len >> sdio->blkbits) == blocknr)) {
+		sdio->cur_page_len += len;
 
 		/*
-		 * If dio->boundary then we want to schedule the IO now to
+		 * If sdio->boundary then we want to schedule the IO now to
 		 * avoid metadata seeks.
 		 */
-		if (dio->boundary) {
-			ret = dio_send_cur_page(dio);
-			page_cache_release(dio->cur_page);
-			dio->cur_page = NULL;
+		if (sdio->boundary) {
+			ret = dio_send_cur_page(dio, sdio);
+			page_cache_release(sdio->cur_page);
+			sdio->cur_page = NULL;
 		}
 		goto out;
 	}

@@ -781,20 +791,20 @@ submit_page_section(struct dio *dio, struct page *page,
 	/*
 	 * If there's a deferred page already there then send it.
 	 */
-	if (dio->cur_page) {
-		ret = dio_send_cur_page(dio);
-		page_cache_release(dio->cur_page);
-		dio->cur_page = NULL;
+	if (sdio->cur_page) {
+		ret = dio_send_cur_page(dio, sdio);
+		page_cache_release(sdio->cur_page);
+		sdio->cur_page = NULL;
 		if (ret)
 			goto out;
 	}
 
 	page_cache_get(page);		/* It is in dio */
-	dio->cur_page = page;
-	dio->cur_page_offset = offset;
-	dio->cur_page_len = len;
-	dio->cur_page_block = blocknr;
-	dio->cur_page_fs_offset = dio->block_in_file << dio->blkbits;
+	sdio->cur_page = page;
+	sdio->cur_page_offset = offset;
+	sdio->cur_page_len = len;
+	sdio->cur_page_block = blocknr;
+	sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
 out:
 	return ret;
 }

@@ -826,19 +836,19 @@ static void clean_blockdev_aliases(struct dio *dio)
  * `end' is zero if we're doing the start of the IO, 1 at the end of the
  * IO.
  */
-static void dio_zero_block(struct dio *dio, int end)
+static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)
 {
 	unsigned dio_blocks_per_fs_block;
 	unsigned this_chunk_blocks;	/* In dio_blocks */
 	unsigned this_chunk_bytes;
 	struct page *page;
 
-	dio->start_zero_done = 1;
-	if (!dio->blkfactor || !buffer_new(&dio->map_bh))
+	sdio->start_zero_done = 1;
+	if (!sdio->blkfactor || !buffer_new(&dio->map_bh))
 		return;
 
-	dio_blocks_per_fs_block = 1 << dio->blkfactor;
-	this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1);
+	dio_blocks_per_fs_block = 1 << sdio->blkfactor;
+	this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
 
 	if (!this_chunk_blocks)
 		return;

@@ -850,14 +860,14 @@ static void dio_zero_block(struct dio *dio, int end)
 	if (end) 
 		this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
 
-	this_chunk_bytes = this_chunk_blocks << dio->blkbits;
+	this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
 
 	page = ZERO_PAGE(0);
-	if (submit_page_section(dio, page, 0, this_chunk_bytes, 
-				dio->next_block_for_io))
+	if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes, 
+				sdio->next_block_for_io))
 		return;
 
-	dio->next_block_for_io += this_chunk_blocks;
+	sdio->next_block_for_io += this_chunk_blocks;
 }
 
 /*

@@ -876,9 +886,9 @@ static void dio_zero_block(struct dio *dio, int end)
  * it should set b_size to PAGE_SIZE or more inside get_block().  This gives
  * fine alignment but still allows this function to work in PAGE_SIZE units.
  */
-static int do_direct_IO(struct dio *dio)
+static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
 {
-	const unsigned blkbits = dio->blkbits;
+	const unsigned blkbits = sdio->blkbits;
 	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
 	struct page *page;
 	unsigned block_in_page;

@@ -886,10 +896,10 @@ static int do_direct_IO(struct dio *dio)
 	int ret = 0;
 
 	/* The I/O can start at any block offset within the first page */
-	block_in_page = dio->first_block_in_page;
+	block_in_page = sdio->first_block_in_page;
 
-	while (dio->block_in_file < dio->final_block_in_request) {
-		page = dio_get_page(dio);
+	while (sdio->block_in_file < sdio->final_block_in_request) {
+		page = dio_get_page(dio, sdio);
 		if (IS_ERR(page)) {
 			ret = PTR_ERR(page);
 			goto out;

@@ -901,14 +911,14 @@ static int do_direct_IO(struct dio *dio)
 			unsigned this_chunk_blocks;	/* # of blocks */
 			unsigned u;
 
-			if (dio->blocks_available == 0) {
+			if (sdio->blocks_available == 0) {
 				/*
 				 * Need to go and map some more disk
 				 */
 				unsigned long blkmask;
 				unsigned long dio_remainder;
 
-				ret = get_more_blocks(dio);
+				ret = get_more_blocks(dio, sdio);
 				if (ret) {
 					page_cache_release(page);
 					goto out;

@@ -916,18 +926,18 @@ static int do_direct_IO(struct dio *dio)
 				if (!buffer_mapped(map_bh))
 					goto do_holes;
 
-				dio->blocks_available =
-						map_bh->b_size >> dio->blkbits;
-				dio->next_block_for_io =
-					map_bh->b_blocknr << dio->blkfactor;
+				sdio->blocks_available =
+						map_bh->b_size >> sdio->blkbits;
+				sdio->next_block_for_io =
+					map_bh->b_blocknr << sdio->blkfactor;
 				if (buffer_new(map_bh))
 					clean_blockdev_aliases(dio);
 
-				if (!dio->blkfactor)
+				if (!sdio->blkfactor)
 					goto do_holes;
 
-				blkmask = (1 << dio->blkfactor) - 1;
-				dio_remainder = (dio->block_in_file & blkmask);
+				blkmask = (1 << sdio->blkfactor) - 1;
+				dio_remainder = (sdio->block_in_file & blkmask);
 
 				/*
 				 * If we are at the start of IO and that IO

@@ -941,8 +951,8 @@ static int do_direct_IO(struct dio *dio)
 				 * on-disk
 				 */
 				if (!buffer_new(map_bh))
-					dio->next_block_for_io += dio_remainder;
-				dio->blocks_available -= dio_remainder;
+					sdio->next_block_for_io += dio_remainder;
+				sdio->blocks_available -= dio_remainder;
 			}
 do_holes:
 			/* Handle holes */

@@ -961,7 +971,7 @@ do_holes:
 				 */
 				i_size_aligned = ALIGN(i_size_read(dio->inode),
 							1 << blkbits);
-				if (dio->block_in_file >=
+				if (sdio->block_in_file >=
 						i_size_aligned >> blkbits) {
 					/* We hit eof */
 					page_cache_release(page);

@@ -969,7 +979,7 @@ do_holes:
 				}
 				zero_user(page, block_in_page << blkbits,
 						1 << blkbits);
-				dio->block_in_file++;
+				sdio->block_in_file++;
 				block_in_page++;
 				goto next_block;
 			}

@@ -979,38 +989,38 @@ do_holes:
 			 * is finer than the underlying fs, go check to see if
 			 * we must zero out the start of this block.
 			 */
-			if (unlikely(dio->blkfactor && !dio->start_zero_done))
-				dio_zero_block(dio, 0);
+			if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
+				dio_zero_block(dio, sdio, 0);
 
 			/*
 			 * Work out, in this_chunk_blocks, how much disk we
 			 * can add to this page
 			 */
-			this_chunk_blocks = dio->blocks_available;
+			this_chunk_blocks = sdio->blocks_available;
 			u = (PAGE_SIZE - offset_in_page) >> blkbits;
 			if (this_chunk_blocks > u)
 				this_chunk_blocks = u;
-			u = dio->final_block_in_request - dio->block_in_file;
+			u = sdio->final_block_in_request - sdio->block_in_file;
 			if (this_chunk_blocks > u)
 				this_chunk_blocks = u;
 			this_chunk_bytes = this_chunk_blocks << blkbits;
 			BUG_ON(this_chunk_bytes == 0);
 
-			dio->boundary = buffer_boundary(map_bh);
-			ret = submit_page_section(dio, page, offset_in_page,
-				this_chunk_bytes, dio->next_block_for_io);
+			sdio->boundary = buffer_boundary(map_bh);
+			ret = submit_page_section(dio, sdio, page, offset_in_page,
+				this_chunk_bytes, sdio->next_block_for_io);
 			if (ret) {
 				page_cache_release(page);
 				goto out;
 			}
-			dio->next_block_for_io += this_chunk_blocks;
+			sdio->next_block_for_io += this_chunk_blocks;
 
-			dio->block_in_file += this_chunk_blocks;
+			sdio->block_in_file += this_chunk_blocks;
 			block_in_page += this_chunk_blocks;
-			dio->blocks_available -= this_chunk_blocks;
+			sdio->blocks_available -= this_chunk_blocks;
 next_block:
-			BUG_ON(dio->block_in_file > dio->final_block_in_request);
-			if (dio->block_in_file == dio->final_block_in_request)
+			BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
+			if (sdio->block_in_file == sdio->final_block_in_request)
 				break;
 		}
 

@@ -1026,7 +1036,7 @@ static ssize_t
 direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, 
 	const struct iovec *iov, loff_t offset, unsigned long nr_segs, 
 	unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
-	dio_submit_t submit_io, struct dio *dio)
+	dio_submit_t submit_io, struct dio *dio, struct dio_submit *sdio)
 {
 	unsigned long user_addr; 
 	unsigned long flags;

@@ -1037,15 +1047,15 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 
 	dio->inode = inode;
 	dio->rw = rw;
-	dio->blkbits = blkbits;
-	dio->blkfactor = inode->i_blkbits - blkbits;
-	dio->block_in_file = offset >> blkbits;
+	sdio->blkbits = blkbits;
+	sdio->blkfactor = inode->i_blkbits - blkbits;
+	sdio->block_in_file = offset >> blkbits;
 
-	dio->get_block = get_block;
+	sdio->get_block = get_block;
 	dio->end_io = end_io;
-	dio->submit_io = submit_io;
-	dio->final_block_in_bio = -1;
-	dio->next_block_for_io = -1;
+	sdio->submit_io = submit_io;
+	sdio->final_block_in_bio = -1;
+	sdio->next_block_for_io = -1;
 
 	dio->iocb = iocb;
 	dio->i_size = i_size_read(inode);

@@ -1057,45 +1067,45 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	 * In case of non-aligned buffers, we may need 2 more
 	 * pages since we need to zero out first and last block.
 	 */
-	if (unlikely(dio->blkfactor))
-		dio->pages_in_io = 2;
+	if (unlikely(sdio->blkfactor))
+		sdio->pages_in_io = 2;
 
 	for (seg = 0; seg < nr_segs; seg++) {
 		user_addr = (unsigned long)iov[seg].iov_base;
-		dio->pages_in_io +=
+		sdio->pages_in_io +=
 			((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
 				- user_addr/PAGE_SIZE);
 	}
 
 	for (seg = 0; seg < nr_segs; seg++) {
 		user_addr = (unsigned long)iov[seg].iov_base;
-		dio->size += bytes = iov[seg].iov_len;
+		sdio->size += bytes = iov[seg].iov_len;
 
 		/* Index into the first page of the first block */
-		dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
-		dio->final_block_in_request = dio->block_in_file +
+		sdio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
+		sdio->final_block_in_request = sdio->block_in_file +
 						(bytes >> blkbits);
 		/* Page fetching state */
-		dio->head = 0;
-		dio->tail = 0;
-		dio->curr_page = 0;
+		sdio->head = 0;
+		sdio->tail = 0;
+		sdio->curr_page = 0;
 
-		dio->total_pages = 0;
+		sdio->total_pages = 0;
 		if (user_addr & (PAGE_SIZE-1)) {
-			dio->total_pages++;
+			sdio->total_pages++;
 			bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
 		}
-		dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
-		dio->curr_user_address = user_addr;
+		sdio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
+		sdio->curr_user_address = user_addr;
 	
-		ret = do_direct_IO(dio);
+		ret = do_direct_IO(dio, sdio);
 
 		dio->result += iov[seg].iov_len -
-			((dio->final_block_in_request - dio->block_in_file) <<
+			((sdio->final_block_in_request - sdio->block_in_file) <<
 					blkbits);
 
 		if (ret) {
-			dio_cleanup(dio);
+			dio_cleanup(dio, sdio);
 			break;
 		}
 	} /* end iovec loop */

@@ -1111,23 +1121,23 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	 * There may be some unwritten disk at the end of a part-written
 	 * fs-block-sized block.  Go zero that now.
 	 */
-	dio_zero_block(dio, 1);
+	dio_zero_block(dio, sdio, 1);
 
-	if (dio->cur_page) {
-		ret2 = dio_send_cur_page(dio);
+	if (sdio->cur_page) {
+		ret2 = dio_send_cur_page(dio, sdio);
 		if (ret == 0)
 			ret = ret2;
-		page_cache_release(dio->cur_page);
-		dio->cur_page = NULL;
+		page_cache_release(sdio->cur_page);
+		sdio->cur_page = NULL;
 	}
-	if (dio->bio)
-		dio_bio_submit(dio);
+	if (sdio->bio)
+		dio_bio_submit(dio, sdio);
 
 	/*
 	 * It is possible that, we return short IO due to end of file.
 	 * In that case, we need to release all the pages we got hold on.
 	 */
-	dio_cleanup(dio);
+	dio_cleanup(dio, sdio);
 
 	/*
 	 * All block lookups have been performed. For READ requests

@@ -1146,7 +1156,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	 */
 	BUG_ON(ret == -EIOCBQUEUED);
 	if (dio->is_async && ret == 0 && dio->result &&
-	    ((rw & READ) || (dio->result == dio->size)))
+	    ((rw & READ) || (dio->result == sdio->size)))
 		ret = -EIOCBQUEUED;
 
 	if (ret != -EIOCBQUEUED)

@@ -1211,6 +1221,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	ssize_t retval = -EINVAL;
 	loff_t end = offset;
 	struct dio *dio;
+	struct dio_submit sdio = { 0, };
 
 	if (rw & WRITE)
 		rw = WRITE_ODIRECT;

@@ -1290,7 +1301,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 
 	retval = direct_io_worker(rw, iocb, inode, iov, offset,
 				nr_segs, blkbits, get_block, end_io,
-				submit_io, dio);
+				  submit_io, dio, &sdio);
 
 out:
 	return retval;

index 02943e3..18e1a14 100644
@@ -39,7 +39,7 @@
 
 /*
  * How many user pages to map in one call to get_user_pages().  This determines
- * the size of a structure on the stack.
+ * the size of a structure in the slab cache
  */
 #define DIO_PAGES	64
 

index 18e1a14..8f23db3 100644
@@ -73,10 +73,10 @@ struct dio_submit {
 	sector_t block_in_file;		/* Current offset into the underlying
 					   file in dio_block units. */
 	unsigned blocks_available;	/* At block_in_file.  changes */
+	int reap_counter;		/* rate limit reaping */
 	sector_t final_block_in_request;/* doesn't change */
 	unsigned first_block_in_page;	/* doesn't change, Used only once */
 	int boundary;			/* prev block is at a boundary */
-	int reap_counter;		/* rate limit reaping */
 	get_block_t *get_block;		/* block mapping function */
 	dio_submit_t *submit_io;	/* IO submition function */	
 

@@ -114,27 +114,26 @@ struct dio_submit {
 /* dio_state communicated between submission path and end_io */
 struct dio {
 	int flags;			/* doesn't change */
-	struct inode *inode;
 	int rw;
+	struct inode *inode;
 	loff_t i_size;			/* i_size when submitted */
 	dio_iodone_t *end_io;		/* IO completion function */
-	struct buffer_head map_bh;	/* last get_block() result */
 
 
 	/* BIO completion state */
 	spinlock_t bio_lock;		/* protects BIO fields below */
+	int page_errors;		/* errno from get_user_pages() */
+	int is_async;			/* is IO async ? */
+	int io_error;			/* IO error in completion path */
 	unsigned long refcount;		/* direct_io_worker() and bios */
 	struct bio *bio_list;		/* singly linked via bi_private */
 	struct task_struct *waiter;	/* waiting task (NULL if none) */
 
 	/* AIO related stuff */
 	struct kiocb *iocb;		/* kiocb */
-	int is_async;			/* is IO async ? */
-	int io_error;			/* IO error in completion path */
 	ssize_t result;                 /* IO result */
 
-	int page_errors;		/* errno from get_user_pages() */
-
+	struct buffer_head map_bh;	/* last get_block() result */
 	/*
 	 * pages[] (and any fields placed after it) are not zeroed out at
 	 * allocation time.  Don't add new fields after pages[] unless you

index 8f23db3..e91ac83 100644
@@ -140,7 +140,9 @@ struct dio {
 	 * wish that they not be zeroed.
 	 */
 	struct page *pages[DIO_PAGES];	/* page buffer */	
-};
+} ____cacheline_aligned_in_smp;
+
+static struct kmem_cache *dio_cache __read_mostly;
 
 static void __inode_dio_wait(struct inode *inode)
 {

@@ -330,7 +332,7 @@ static void dio_bio_end_aio(struct bio *bio, int error)
 
 	if (remaining == 0) {
 		dio_complete(dio, dio->iocb->ki_pos, 0, true);
-		kfree(dio);
+		kmem_cache_free(dio_cache, dio);
 	}
 }
 

@@ -1178,7 +1180,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 
 	if (ret2 == 0) {
 		ret = dio_complete(dio, offset, ret, false);
-		kfree(dio);
+		kmem_cache_free(dio_cache, dio);
 	} else
 		BUG_ON(ret != -EIOCBQUEUED);
 

@@ -1254,7 +1256,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	if (rw == READ && end == offset)
 		return 0;
 
-	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
+	dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
 	retval = -ENOMEM;
 	if (!dio)
 		goto out;

@@ -1278,7 +1280,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 							      end - 1);
 			if (retval) {
 				mutex_unlock(&inode->i_mutex);
-				kfree(dio);
+				kmem_cache_free(dio_cache, dio);
 				goto out;
 			}
 		}

@@ -1306,3 +1308,10 @@ out:
 	return retval;
 }
 EXPORT_SYMBOL(__blockdev_direct_IO);
+
+static __init int dio_init(void)
+{
+	dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
+	return 0;
+}
+module_init(dio_init)

index e91ac83..172ec77 100644
@@ -119,6 +119,7 @@ struct dio {
 	loff_t i_size;			/* i_size when submitted */
 	dio_iodone_t *end_io;		/* IO completion function */
 
+	void *private;			/* copy from map_bh.b_private */
 
 	/* BIO completion state */
 	spinlock_t bio_lock;		/* protects BIO fields below */

@@ -133,7 +134,6 @@ struct dio {
 	struct kiocb *iocb;		/* kiocb */
 	ssize_t result;                 /* IO result */
 
-	struct buffer_head map_bh;	/* last get_block() result */
 	/*
 	 * pages[] (and any fields placed after it) are not zeroed out at
 	 * allocation time.  Don't add new fields after pages[] unless you

@@ -301,7 +301,7 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is
 
 	if (dio->end_io && dio->result) {
 		dio->end_io(dio->iocb, offset, transferred,
-			    dio->map_bh.b_private, ret, is_async);
+			    dio->private, ret, is_async);
 	} else {
 		if (is_async)
 			aio_complete(dio->iocb, ret, 0);

@@ -574,10 +574,10 @@ static int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
  * buffer_mapped().  However the direct-io code will only process holes one
  * block at a time - it will repeatedly call get_block() as it walks the hole.
  */
-static int get_more_blocks(struct dio *dio, struct dio_submit *sdio)
+static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
+			   struct buffer_head *map_bh)
 {
 	int ret;
-	struct buffer_head *map_bh = &dio->map_bh;
 	sector_t fs_startblk;	/* Into file, in filesystem-sized blocks */
 	unsigned long fs_count;	/* Number of filesystem-sized blocks */
 	unsigned long dio_count;/* Number of dio_block-sized blocks */

@@ -621,6 +621,9 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio)
 
 		ret = (*sdio->get_block)(dio->inode, fs_startblk,
 						map_bh, create);
+
+		/* Store for completion */
+		dio->private = map_bh->b_private;
 	}
 	return ret;
 }

@@ -629,7 +632,7 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio)
  * There is no bio.  Make one now.
  */
 static int dio_new_bio(struct dio *dio, struct dio_submit *sdio, 
-		       sector_t start_sector)
+		       sector_t start_sector, struct buffer_head *map_bh)
 {
 	sector_t sector;
 	int ret, nr_pages;

@@ -638,10 +641,10 @@ static int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
 	if (ret)
 		goto out;
 	sector = start_sector << (sdio->blkbits - 9);
-	nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev));
+	nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(map_bh->b_bdev));
 	nr_pages = min(nr_pages, BIO_MAX_PAGES);
 	BUG_ON(nr_pages <= 0);
-	dio_bio_alloc(dio, sdio, dio->map_bh.b_bdev, sector, nr_pages);
+	dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
 	sdio->boundary = 0;
 out:
 	return ret;

@@ -686,7 +689,8 @@ static int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)
  * The caller of this function is responsible for removing cur_page from the
  * dio, and for dropping the refcount which came from that presence.
  */
-static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio)
+static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
+			     struct buffer_head *map_bh)
 {
 	int ret = 0;
 

@@ -721,14 +725,14 @@ static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio)
 	}
 
 	if (sdio->bio == NULL) {
-		ret = dio_new_bio(dio, sdio, sdio->cur_page_block);
+		ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
 		if (ret)
 			goto out;
 	}
 
 	if (dio_bio_add_page(dio, sdio) != 0) {
 		dio_bio_submit(dio, sdio);
-		ret = dio_new_bio(dio, sdio, sdio->cur_page_block);
+		ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
 		if (ret == 0) {
 			ret = dio_bio_add_page(dio, sdio);
 			BUG_ON(ret != 0);

@@ -757,7 +761,8 @@ out:
  */
 static int
 submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
-		unsigned offset, unsigned len, sector_t blocknr)
+		    unsigned offset, unsigned len, sector_t blocknr,
+		    struct buffer_head *map_bh)
 {
 	int ret = 0;
 

@@ -782,7 +787,7 @@ submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
 		 * avoid metadata seeks.
 		 */
 		if (sdio->boundary) {
-			ret = dio_send_cur_page(dio, sdio);
+			ret = dio_send_cur_page(dio, sdio, map_bh);
 			page_cache_release(sdio->cur_page);
 			sdio->cur_page = NULL;
 		}

@@ -793,7 +798,7 @@ submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
 	 * If there's a deferred page already there then send it.
 	 */
 	if (sdio->cur_page) {
-		ret = dio_send_cur_page(dio, sdio);
+		ret = dio_send_cur_page(dio, sdio, map_bh);
 		page_cache_release(sdio->cur_page);
 		sdio->cur_page = NULL;
 		if (ret)

@@ -815,16 +820,16 @@ out:
  * file blocks.  Only called for S_ISREG files - blockdevs do not set
  * buffer_new
  */
-static void clean_blockdev_aliases(struct dio *dio)
+static void clean_blockdev_aliases(struct dio *dio, struct buffer_head *map_bh)
 {
 	unsigned i;
 	unsigned nblocks;
 
-	nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits;
+	nblocks = map_bh->b_size >> dio->inode->i_blkbits;
 
 	for (i = 0; i < nblocks; i++) {
-		unmap_underlying_metadata(dio->map_bh.b_bdev,
-					dio->map_bh.b_blocknr + i);
+		unmap_underlying_metadata(map_bh->b_bdev,
+					  map_bh->b_blocknr + i);
 	}
 }
 

@@ -837,7 +842,8 @@ static void clean_blockdev_aliases(struct dio *dio)
  * `end' is zero if we're doing the start of the IO, 1 at the end of the
  * IO.
  */
-static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)
+static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end,
+			   struct buffer_head *map_bh)
 {
 	unsigned dio_blocks_per_fs_block;
 	unsigned this_chunk_blocks;	/* In dio_blocks */

@@ -845,7 +851,7 @@ static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)
 	struct page *page;
 
 	sdio->start_zero_done = 1;
-	if (!sdio->blkfactor || !buffer_new(&dio->map_bh))
+	if (!sdio->blkfactor || !buffer_new(map_bh))
 		return;
 
 	dio_blocks_per_fs_block = 1 << sdio->blkfactor;

@@ -865,7 +871,7 @@ static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)
 
 	page = ZERO_PAGE(0);
 	if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes, 
-				sdio->next_block_for_io))
+				sdio->next_block_for_io, map_bh))
 		return;
 
 	sdio->next_block_for_io += this_chunk_blocks;

@@ -887,13 +893,13 @@ static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end)
  * it should set b_size to PAGE_SIZE or more inside get_block().  This gives
  * fine alignment but still allows this function to work in PAGE_SIZE units.
  */
-static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
+static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
+			struct buffer_head *map_bh)
 {
 	const unsigned blkbits = sdio->blkbits;
 	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
 	struct page *page;
 	unsigned block_in_page;
-	struct buffer_head *map_bh = &dio->map_bh;
 	int ret = 0;
 
 	/* The I/O can start at any block offset within the first page */

@@ -919,7 +925,7 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
 				unsigned long blkmask;
 				unsigned long dio_remainder;
 
-				ret = get_more_blocks(dio, sdio);
+				ret = get_more_blocks(dio, sdio, map_bh);
 				if (ret) {
 					page_cache_release(page);
 					goto out;

@@ -932,7 +938,7 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio)
 				sdio->next_block_for_io =
 					map_bh->b_blocknr << sdio->blkfactor;
 				if (buffer_new(map_bh))
-					clean_blockdev_aliases(dio);
+					clean_blockdev_aliases(dio, map_bh);
 
 				if (!sdio->blkfactor)
 					goto do_holes;

@@ -991,7 +997,7 @@ do_holes:
 			 * we must zero out the start of this block.
 			 */
 			if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
-				dio_zero_block(dio, sdio, 0);
+				dio_zero_block(dio, sdio, 0, map_bh);
 
 			/*
 			 * Work out, in this_chunk_blocks, how much disk we

@@ -1009,7 +1015,7 @@ do_holes:
 
 			sdio->boundary = buffer_boundary(map_bh);
 			ret = submit_page_section(dio, sdio, page, offset_in_page,
-				this_chunk_bytes, sdio->next_block_for_io);
+				  this_chunk_bytes, sdio->next_block_for_io, map_bh);
 			if (ret) {
 				page_cache_release(page);
 				goto out;

@@ -1045,6 +1051,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	ssize_t ret = 0;
 	ssize_t ret2;
 	size_t bytes;
+	struct buffer_head map_bh = { 0, };
 
 	dio->inode = inode;
 	dio->rw = rw;

@@ -1099,7 +1106,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 		sdio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
 		sdio->curr_user_address = user_addr;
 	
-		ret = do_direct_IO(dio, sdio);
+		ret = do_direct_IO(dio, sdio, &map_bh);
 
 		dio->result += iov[seg].iov_len -
 			((sdio->final_block_in_request - sdio->block_in_file) <<

@@ -1122,10 +1129,10 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	 * There may be some unwritten disk at the end of a part-written
 	 * fs-block-sized block.  Go zero that now.
 	 */
-	dio_zero_block(dio, sdio, 1);
+	dio_zero_block(dio, sdio, 1, &map_bh);
 
 	if (sdio->cur_page) {
-		ret2 = dio_send_cur_page(dio, sdio);
+		ret2 = dio_send_cur_page(dio, sdio, &map_bh);
 		if (ret == 0)
 			ret = ret2;
 		page_cache_release(sdio->cur_page);

index 172ec77..103a6fc 100644
@@ -199,7 +199,7 @@ static inline unsigned dio_pages_present(struct dio *dio, struct dio_submit *sdi
 /*
  * Go grab and pin some userspace pages.   Typically we'll get 64 at a time.
  */
-static int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
+static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret;
 	int nr_pages;

@@ -245,7 +245,7 @@ out:
  * decent number of pages, less frequently.  To provide nicer use of the
  * L1 cache.
  */
-static struct page *dio_get_page(struct dio *dio, struct dio_submit *sdio)
+static inline struct page *dio_get_page(struct dio *dio, struct dio_submit *sdio)
 {
 	if (dio_pages_present(dio, sdio) == 0) {
 		int ret;

@@ -376,7 +376,7 @@ void dio_end_io(struct bio *bio, int error)
 }
 EXPORT_SYMBOL_GPL(dio_end_io);
 
-static void
+static void inline
 dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
 	      struct block_device *bdev,
 	      sector_t first_sector, int nr_vecs)

@@ -407,7 +407,7 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
  *
  * bios hold a dio reference between submit_bio and ->end_io.
  */
-static void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
+static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
 {
 	struct bio *bio = sdio->bio;
 	unsigned long flags;

@@ -435,7 +435,7 @@ static void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
 /*
  * Release any resources in case of a failure
  */
-static void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
+static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
 {
 	while (dio_pages_present(dio, sdio))
 		page_cache_release(dio_get_page(dio, sdio));

@@ -528,7 +528,7 @@ static void dio_await_completion(struct dio *dio)
  *
  * This also helps to limit the peak amount of pinned userspace memory.
  */
-static int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
+static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret = 0;
 

@@ -631,7 +631,7 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
 /*
  * There is no bio.  Make one now.
  */
-static int dio_new_bio(struct dio *dio, struct dio_submit *sdio, 
+static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio, 
 		       sector_t start_sector, struct buffer_head *map_bh)
 {
 	sector_t sector;

@@ -657,7 +657,7 @@ out:
  *
  * Return zero on success.  Non-zero means the caller needs to start a new BIO.
  */
-static int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)
+static inline int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)
 {
 	int ret;
 

@@ -689,8 +689,8 @@ static int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)
  * The caller of this function is responsible for removing cur_page from the
  * dio, and for dropping the refcount which came from that presence.
  */
-static int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
-			     struct buffer_head *map_bh)
+static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
+	  		    	    struct buffer_head *map_bh)
 {
 	int ret = 0;
 

@@ -759,7 +759,7 @@ out:
  * If that doesn't work out then we put the old page into the bio and add this
  * page to the dio instead.
  */
-static int
+static inline int
 submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
 		    unsigned offset, unsigned len, sector_t blocknr,
 		    struct buffer_head *map_bh)

@@ -842,7 +842,7 @@ static void clean_blockdev_aliases(struct dio *dio, struct buffer_head *map_bh)
  * `end' is zero if we're doing the start of the IO, 1 at the end of the
  * IO.
  */
-static void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end,
+static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio, int end,
 			   struct buffer_head *map_bh)
 {
 	unsigned dio_blocks_per_fs_block;

@@ -1039,7 +1039,7 @@ out:
 	return ret;
 }
 
-static ssize_t
+static inline ssize_t
 direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, 
 	const struct iovec *iov, loff_t offset, unsigned long nr_segs, 
 	unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,

@@ -1213,6 +1213,11 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
  * expected that filesystem provide exclusion between new direct I/O
  * and truncates.  For DIO_LOCKING filesystems this is done by i_mutex,
  * but other filesystems need to take care of this on their own.
+ * 
+ * NOTE: if you pass "sdio" to anything by pointer make sure that function
+ * is always inlined. Otherwise gcc is unable to split the structure into
+ * individual fields and will generate much worse code. 
+ * This is important for the whole file.
  */
 ssize_t
 __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,

index 103a6fc..669b667 100644
@@ -1039,136 +1039,10 @@ out:
 	return ret;
 }
 
-static inline ssize_t
-direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, 
-	const struct iovec *iov, loff_t offset, unsigned long nr_segs, 
-	unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
-	dio_submit_t submit_io, struct dio *dio, struct dio_submit *sdio)
+static inline int drop_refcount(struct dio *dio)
 {
-	unsigned long user_addr; 
+	int ret2;
 	unsigned long flags;
-	int seg;
-	ssize_t ret = 0;
-	ssize_t ret2;
-	size_t bytes;
-	struct buffer_head map_bh = { 0, };
-
-	dio->inode = inode;
-	dio->rw = rw;
-	sdio->blkbits = blkbits;
-	sdio->blkfactor = inode->i_blkbits - blkbits;
-	sdio->block_in_file = offset >> blkbits;
-
-	sdio->get_block = get_block;
-	dio->end_io = end_io;
-	sdio->submit_io = submit_io;
-	sdio->final_block_in_bio = -1;
-	sdio->next_block_for_io = -1;
-
-	dio->iocb = iocb;
-	dio->i_size = i_size_read(inode);
-
-	spin_lock_init(&dio->bio_lock);
-	dio->refcount = 1;
-
-	/*
-	 * In case of non-aligned buffers, we may need 2 more
-	 * pages since we need to zero out first and last block.
-	 */
-	if (unlikely(sdio->blkfactor))
-		sdio->pages_in_io = 2;
-
-	for (seg = 0; seg < nr_segs; seg++) {
-		user_addr = (unsigned long)iov[seg].iov_base;
-		sdio->pages_in_io +=
-			((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
-				- user_addr/PAGE_SIZE);
-	}
-
-	for (seg = 0; seg < nr_segs; seg++) {
-		user_addr = (unsigned long)iov[seg].iov_base;
-		sdio->size += bytes = iov[seg].iov_len;
-
-		/* Index into the first page of the first block */
-		sdio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
-		sdio->final_block_in_request = sdio->block_in_file +
-						(bytes >> blkbits);
-		/* Page fetching state */
-		sdio->head = 0;
-		sdio->tail = 0;
-		sdio->curr_page = 0;
-
-		sdio->total_pages = 0;
-		if (user_addr & (PAGE_SIZE-1)) {
-			sdio->total_pages++;
-			bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
-		}
-		sdio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
-		sdio->curr_user_address = user_addr;
-	
-		ret = do_direct_IO(dio, sdio, &map_bh);
-
-		dio->result += iov[seg].iov_len -
-			((sdio->final_block_in_request - sdio->block_in_file) <<
-					blkbits);
-
-		if (ret) {
-			dio_cleanup(dio, sdio);
-			break;
-		}
-	} /* end iovec loop */
-
-	if (ret == -ENOTBLK) {
-		/*
-		 * The remaining part of the request will be
-		 * be handled by buffered I/O when we return
-		 */
-		ret = 0;
-	}
-	/*
-	 * There may be some unwritten disk at the end of a part-written
-	 * fs-block-sized block.  Go zero that now.
-	 */
-	dio_zero_block(dio, sdio, 1, &map_bh);
-
-	if (sdio->cur_page) {
-		ret2 = dio_send_cur_page(dio, sdio, &map_bh);
-		if (ret == 0)
-			ret = ret2;
-		page_cache_release(sdio->cur_page);
-		sdio->cur_page = NULL;
-	}
-	if (sdio->bio)
-		dio_bio_submit(dio, sdio);
-
-	/*
-	 * It is possible that, we return short IO due to end of file.
-	 * In that case, we need to release all the pages we got hold on.
-	 */
-	dio_cleanup(dio, sdio);
-
-	/*
-	 * All block lookups have been performed. For READ requests
-	 * we can let i_mutex go now that its achieved its purpose
-	 * of protecting us from looking up uninitialized blocks.
-	 */
-	if (rw == READ && (dio->flags & DIO_LOCKING))
-		mutex_unlock(&dio->inode->i_mutex);
-
-	/*
-	 * The only time we want to leave bios in flight is when a successful
-	 * partial aio read or full aio write have been setup.  In that case
-	 * bio completion will call aio_complete.  The only time it's safe to
-	 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
-	 * This had *better* be the only place that raises -EIOCBQUEUED.
-	 */
-	BUG_ON(ret == -EIOCBQUEUED);
-	if (dio->is_async && ret == 0 && dio->result &&
-	    ((rw & READ) || (dio->result == sdio->size)))
-		ret = -EIOCBQUEUED;
-
-	if (ret != -EIOCBQUEUED)
-		dio_await_completion(dio);
 
 	/*
 	 * Sync will always be dropping the final ref and completing the

@@ -1184,14 +1058,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
 	spin_lock_irqsave(&dio->bio_lock, flags);
 	ret2 = --dio->refcount;
 	spin_unlock_irqrestore(&dio->bio_lock, flags);
-
-	if (ret2 == 0) {
-		ret = dio_complete(dio, offset, ret, false);
-		kmem_cache_free(dio_cache, dio);
-	} else
-		BUG_ON(ret != -EIOCBQUEUED);
-
-	return ret;
+	return ret2;
 }
 
 /*

@@ -1235,6 +1102,9 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	loff_t end = offset;
 	struct dio *dio;
 	struct dio_submit sdio = { 0, };
+	unsigned long user_addr; 
+	size_t bytes;
+	struct buffer_head map_bh = { 0, };
 
 	if (rw & WRITE)
 		rw = WRITE_ODIRECT;

@@ -1312,9 +1182,132 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
 		(end > i_size_read(inode)));
 
-	retval = direct_io_worker(rw, iocb, inode, iov, offset,
-				nr_segs, blkbits, get_block, end_io,
-				  submit_io, dio, &sdio);
+	retval = 0;
+
+	dio->inode = inode;
+	dio->rw = rw;
+	sdio.blkbits = blkbits;
+	sdio.blkfactor = inode->i_blkbits - blkbits;
+	sdio.block_in_file = offset >> blkbits;
+
+	sdio.get_block = get_block;
+	dio->end_io = end_io;
+	sdio.submit_io = submit_io;
+	sdio.final_block_in_bio = -1;
+	sdio.next_block_for_io = -1;
+
+	dio->iocb = iocb;
+	dio->i_size = i_size_read(inode);
+
+	spin_lock_init(&dio->bio_lock);
+	dio->refcount = 1;
+
+	/*
+	 * In case of non-aligned buffers, we may need 2 more
+	 * pages since we need to zero out first and last block.
+	 */
+	if (unlikely(sdio.blkfactor))
+		sdio.pages_in_io = 2;
+
+	for (seg = 0; seg < nr_segs; seg++) {
+		user_addr = (unsigned long)iov[seg].iov_base;
+		sdio.pages_in_io +=
+			((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE
+				- user_addr/PAGE_SIZE);
+	}
+
+	for (seg = 0; seg < nr_segs; seg++) {
+		user_addr = (unsigned long)iov[seg].iov_base;
+		sdio.size += bytes = iov[seg].iov_len;
+
+		/* Index into the first page of the first block */
+		sdio.first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits;
+		sdio.final_block_in_request = sdio.block_in_file +
+						(bytes >> blkbits);
+		/* Page fetching state */
+		sdio.head = 0;
+		sdio.tail = 0;
+		sdio.curr_page = 0;
+
+		sdio.total_pages = 0;
+		if (user_addr & (PAGE_SIZE-1)) {
+			sdio.total_pages++;
+			bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
+		}
+		sdio.total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
+		sdio.curr_user_address = user_addr;
+	
+		retval = do_direct_IO(dio, &sdio, &map_bh);
+
+		dio->result += iov[seg].iov_len -
+			((sdio.final_block_in_request - sdio.block_in_file) <<
+					blkbits);
+
+		if (retval) {
+			dio_cleanup(dio, &sdio);
+			break;
+		}
+	} /* end iovec loop */
+
+	if (retval == -ENOTBLK) {
+		/*
+		 * The remaining part of the request will be
+		 * be handled by buffered I/O when we return
+		 */
+		retval = 0;
+	}
+	/*
+	 * There may be some unwritten disk at the end of a part-written
+	 * fs-block-sized block.  Go zero that now.
+	 */
+	dio_zero_block(dio, &sdio, 1, &map_bh);
+
+	if (sdio.cur_page) {
+		ssize_t ret2;
+
+		ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
+		if (retval == 0)
+			retval = ret2;
+		page_cache_release(sdio.cur_page);
+		sdio.cur_page = NULL;
+	}
+	if (sdio.bio)
+		dio_bio_submit(dio, &sdio);
+
+	/*
+	 * It is possible that, we return short IO due to end of file.
+	 * In that case, we need to release all the pages we got hold on.
+	 */
+	dio_cleanup(dio, &sdio);
+
+	/*
+	 * All block lookups have been performed. For READ requests
+	 * we can let i_mutex go now that its achieved its purpose
+	 * of protecting us from looking up uninitialized blocks.
+	 */
+	if (rw == READ && (dio->flags & DIO_LOCKING))
+		mutex_unlock(&dio->inode->i_mutex);
+
+	/*
+	 * The only time we want to leave bios in flight is when a successful
+	 * partial aio read or full aio write have been setup.  In that case
+	 * bio completion will call aio_complete.  The only time it's safe to
+	 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
+	 * This had *better* be the only place that raises -EIOCBQUEUED.
+	 */
+	BUG_ON(retval == -EIOCBQUEUED);
+	if (dio->is_async && retval == 0 && dio->result &&
+	    ((rw & READ) || (dio->result == sdio.size)))
+		retval = -EIOCBQUEUED;
+
+	if (retval != -EIOCBQUEUED)
+		dio_await_completion(dio);
+
+	if (drop_refcount(dio) == 0) {
+		retval = dio_complete(dio, offset, retval, false);
+		kmem_cache_free(dio_cache, dio);
+	} else
+		BUG_ON(retval != -EIOCBQUEUED);
 
 out:
 	return retval;

index 669b667..3f5d1b4 100644
@@ -191,7 +191,7 @@ EXPORT_SYMBOL_GPL(inode_dio_done);
 /*
  * How many pages are in the queue?
  */
-static inline unsigned dio_pages_present(struct dio *dio, struct dio_submit *sdio)
+static inline unsigned dio_pages_present(struct dio_submit *sdio)
 {
 	return sdio->tail - sdio->head;
 }

@@ -247,13 +247,13 @@ out:
  */
 static inline struct page *dio_get_page(struct dio *dio, struct dio_submit *sdio)
 {
-	if (dio_pages_present(dio, sdio) == 0) {
+	if (dio_pages_present(sdio) == 0) {
 		int ret;
 
 		ret = dio_refill_pages(dio, sdio);
 		if (ret)
 			return ERR_PTR(ret);
-		BUG_ON(dio_pages_present(dio, sdio) == 0);
+		BUG_ON(dio_pages_present(sdio) == 0);
 	}
 	return dio->pages[sdio->head++];
 }

@@ -437,7 +437,7 @@ static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
  */
 static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
 {
-	while (dio_pages_present(dio, sdio))
+	while (dio_pages_present(sdio))
 		page_cache_release(dio_get_page(dio, sdio));
 }
 

index 3f5d1b4..03bcc6f 100644
@@ -657,7 +657,7 @@ out:
  *
  * Return zero on success.  Non-zero means the caller needs to start a new BIO.
  */
-static inline int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)
+static inline int dio_bio_add_page(struct dio_submit *sdio)
 {
 	int ret;
 

@@ -730,11 +730,11 @@ static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
 			goto out;
 	}
 
-	if (dio_bio_add_page(dio, sdio) != 0) {
+	if (dio_bio_add_page(sdio) != 0) {
 		dio_bio_submit(dio, sdio);
 		ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
 		if (ret == 0) {
-			ret = dio_bio_add_page(dio, sdio);
+			ret = dio_bio_add_page(sdio);
 			BUG_ON(ret != 0);
 		}
 	}

index ff77262..f9899d5 100644
@@ -1115,6 +1115,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 	mutex_lock_nested(&bdev->bd_mutex, for_part);
 	if (!bdev->bd_openers) {
 		bdev->bd_disk = disk;
+		bdev->bd_queue = disk->queue;
 		bdev->bd_contains = bdev;
 		if (!partno) {
 			struct backing_dev_info *bdi;

@@ -1135,6 +1136,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 					disk_put_part(bdev->bd_part);
 					bdev->bd_part = NULL;
 					bdev->bd_disk = NULL;
+					bdev->bd_queue = NULL;
 					mutex_unlock(&bdev->bd_mutex);
 					disk_unblock_events(disk);
 					module_put(disk->fops->owner);

@@ -1208,6 +1210,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 	disk_put_part(bdev->bd_part);
 	bdev->bd_disk = NULL;
 	bdev->bd_part = NULL;
+	bdev->bd_queue = NULL;
 	bdev_inode_switch_bdi(bdev->bd_inode, &default_backing_dev_info);
 	if (bdev != bdev->bd_contains)
 		__blkdev_put(bdev->bd_contains, mode, 1);

index 178cdb4..7d8c1f9 100644
@@ -657,6 +657,7 @@ struct address_space {
 	 * must be enforced here for CRIS, to let the least significant bit
 	 * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
 	 */
+struct request_queue;
 
 struct block_device {
 	dev_t			bd_dev;  /* not a kdev_t - it's a search key */

@@ -679,6 +680,7 @@ struct block_device {
 	unsigned		bd_part_count;
 	int			bd_invalidated;
 	struct gendisk *	bd_disk;
+	struct request_queue *  bd_queue;
 	struct list_head	bd_list;
 	/*
 	 * Private data.  You must have bd_claim'ed the block_device

index 03bcc6f..e149f5f 100644
@@ -1086,8 +1086,8 @@ static inline int drop_refcount(struct dio *dio)
  * individual fields and will generate much worse code. 
  * This is important for the whole file.
  */
-ssize_t
-__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
+static inline ssize_t
+do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	struct block_device *bdev, const struct iovec *iov, loff_t offset, 
 	unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
 	dio_submit_t submit_io,	int flags)

@@ -1096,7 +1096,6 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	size_t size;
 	unsigned long addr;
 	unsigned blkbits = inode->i_blkbits;
-	unsigned bdev_blkbits = 0;
 	unsigned blocksize_mask = (1 << blkbits) - 1;
 	ssize_t retval = -EINVAL;
 	loff_t end = offset;

@@ -1109,12 +1108,14 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	if (rw & WRITE)
 		rw = WRITE_ODIRECT;
 
-	if (bdev)
-		bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev));
+	/* 
+	 * Avoid references to bdev if not absolutely needed to give
+	 * the early prefetch in the caller enough time.
+	 */
 
 	if (offset & blocksize_mask) {
 		if (bdev)
-			 blkbits = bdev_blkbits;
+			blkbits = blksize_bits(bdev_logical_block_size(bdev));
 		blocksize_mask = (1 << blkbits) - 1;
 		if (offset & blocksize_mask)
 			goto out;

@@ -1125,11 +1126,13 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 		addr = (unsigned long)iov[seg].iov_base;
 		size = iov[seg].iov_len;
 		end += size;
-		if ((addr & blocksize_mask) || (size & blocksize_mask))  {
+		if (unlikely((addr & blocksize_mask) || 
+			     (size & blocksize_mask)))  {
 			if (bdev)
-				 blkbits = bdev_blkbits;
+				 blkbits = blksize_bits(
+					 bdev_logical_block_size(bdev));
 			blocksize_mask = (1 << blkbits) - 1;
-			if ((addr & blocksize_mask) || (size & blocksize_mask))  
+			if ((addr & blocksize_mask) || (size & blocksize_mask))
 				goto out;
 		}
 	}

@@ -1312,6 +1315,30 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 out:
 	return retval;
 }
+
+ssize_t
+__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
+	struct block_device *bdev, const struct iovec *iov, loff_t offset, 
+	unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
+	dio_submit_t submit_io,	int flags)
+{
+	/* 
+	 * The block device state is needed in the end to finally
+	 * submit everything.  Since it's likely to be cache cold
+	 * prefetch it here as first thing to hide some of the
+	 * latency.
+	 * 
+	 * Attempt to prefetch the pieces we likely need later.
+	 */
+	prefetch(&bdev->bd_disk->part_tbl);
+	prefetch(bdev->bd_queue);
+	prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
+
+	return do_blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
+				     nr_segs, get_block, end_io,
+				     submit_io, flags);
+}
+
 EXPORT_SYMBOL(__blockdev_direct_IO);
 
 static __init int dio_init(void)