use atomic kmaps in generic_file_write

This patch uses the kmap_copy_user() API across generic_file_write()'s copy_*_user().

This required a change in the prepare_write/commit_write API definition. It is no longer the case that these functions will kmap the page for you.

If any part of the kernel wants to get at the page in the write path, it now has to kmap it for itself. The best way to do this is with kmap_atomic(KM_USER0).

This patch updates all callers. It also converts several places which were unnecessarily using kmap() over to using kmap_atomic().

I made a bit of a mess of reiserfs. It works OK, but I suspect it's performing unnecessary kmaps.

The patch has been tested with loop, ext2, ext3, reiserfs, jfs, minixfs, vfat, iso9660, nfs and the ramdisk driver.

drivers/block/loop.c  |    5 ++--
drivers/block/rd.c    |   19 +++++++++++-----
fs/affs/file.c        |   11 ++++++++-
fs/buffer.c           |   57 ++++++++++++++++++++++++++++----------------------
fs/driverfs/inode.c   |    6 ++---
fs/ext2/dir.c         |   11 ++++-----
fs/ext3/inode.c       |   30 +++++---------------------
fs/fat/inode.c        |   17 +++++++++++++-
fs/jffs/inode-v23.c   |   11 ++++++---
fs/jffs2/file.c       |    4 ++-
fs/jfs/jfs_metapage.c |    1 fs/minix/dir.c        |   12 ++++++----
fs/namei.c            |    3 +-
fs/ramfs/inode.c      |   14 +++++++-----
fs/reiserfs/inode.c   |   27 ++++++++++++++++-------
fs/sysv/dir.c         |    3 ++
mm/filemap.c          |    6 ++---
17 files changed, 140 insertions, 97 deletions

mm/filemap.c renamed from mm/filemap.c~kmap_atomic_writes +3 -3

@@ -1969,6 +1969,7 @@ generic_file_write(struct file *file, co
 		unsigned long offset;
 		long page_fault;
 		char *kaddr;
+		struct copy_user_state copy_user_state;
 
 		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
 		index = pos >> PAGE_CACHE_SHIFT;

@@ -1993,22 +1994,22 @@ generic_file_write(struct file *file, co
 			break;
 		}
 
-		kaddr = kmap(page);
 		status = a_ops->prepare_write(file, page, offset, offset+bytes);
 		if (unlikely(status)) {
 			/*
 			 * prepare_write() may have instantiated a few blocks
 			 * outside i_size.  Trim these off again.
 			 */
-			kunmap(page);
 			unlock_page(page);
 			page_cache_release(page);
 			if (pos + bytes > inode->i_size)
 				vmtruncate(inode, inode->i_size);
 			break;
 		}
+		kaddr = kmap_copy_user(&copy_user_state, page, KM_FILEMAP, 0);
 		page_fault = __copy_from_user(kaddr + offset, buf, bytes);
 		flush_dcache_page(page);
+		kunmap_copy_user(&copy_user_state);
 		status = a_ops->commit_write(file, page, offset, offset+bytes);
 		if (unlikely(page_fault)) {
 			status = -EFAULT;

@@ -2023,7 +2024,6 @@ generic_file_write(struct file *file, co
 				buf += status;
 			}
 		}
-		kunmap(page);
 		if (!PageReferenced(page))
 			SetPageReferenced(page);
 		unlock_page(page);

fs/buffer.c renamed from fs/buffer.c~kmap_atomic_writes +24 -13

@@ -1798,7 +1798,6 @@ static int __block_prepare_write(struct 
 	int err = 0;
 	unsigned blocksize, bbits;
 	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
-	char *kaddr = kmap(page);
 
 	BUG_ON(!PageLocked(page));
 	BUG_ON(from > PAGE_CACHE_SIZE);

@@ -1839,13 +1838,19 @@ static int __block_prepare_write(struct 
 					set_buffer_uptodate(bh);
 					continue;
 				}
-				if (block_end > to)
-					memset(kaddr+to, 0, block_end-to);
-				if (block_start < from)
-					memset(kaddr+block_start,
-						0, from-block_start);
-				if (block_end > to || block_start < from)
+				if (block_end > to || block_start < from) {
+					void *kaddr;
+
+					kaddr = kmap_atomic(page, KM_USER0);
+					if (block_end > to)
+						memset(kaddr+to, 0,
+							block_end-to);
+					if (block_start < from)
+						memset(kaddr+block_start,
+							0, from-block_start);
 					flush_dcache_page(page);
+					kunmap_atomic(kaddr, KM_USER0);
+				}
 				continue;
 			}
 		}

@@ -1884,10 +1889,14 @@ out:
 		if (block_start >= to)
 			break;
 		if (buffer_new(bh)) {
+			void *kaddr;
+
 			clear_buffer_new(bh);
 			if (buffer_uptodate(bh))
 				buffer_error();
+			kaddr = kmap_atomic(page, KM_USER0);
 			memset(kaddr+block_start, 0, bh->b_size);
+			kunmap_atomic(kaddr, KM_USER0);
 			set_buffer_uptodate(bh);
 			mark_buffer_dirty(bh);
 		}

@@ -1973,9 +1982,10 @@ int block_read_full_page(struct page *pa
 					SetPageError(page);
 			}
 			if (!buffer_mapped(bh)) {
-				memset(kmap(page) + i*blocksize, 0, blocksize);
+				void *kaddr = kmap_atomic(page, KM_USER0);
+				memset(kaddr + i * blocksize, 0, blocksize);
 				flush_dcache_page(page);
-				kunmap(page);
+				kunmap_atomic(kaddr, KM_USER0);
 				set_buffer_uptodate(bh);
 				continue;
 			}

@@ -2083,7 +2093,7 @@ int cont_prepare_write(struct page *page
 	long status;
 	unsigned zerofrom;
 	unsigned blocksize = 1 << inode->i_blkbits;
-	char *kaddr;
+	void *kaddr;
 
 	while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
 		status = -ENOMEM;

@@ -2105,12 +2115,12 @@ int cont_prepare_write(struct page *page
 						PAGE_CACHE_SIZE, get_block);
 		if (status)
 			goto out_unmap;
-		kaddr = page_address(new_page);
+		kaddr = kmap_atomic(new_page, KM_USER0);
 		memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
 		flush_dcache_page(new_page);
+		kunmap_atomic(kaddr, KM_USER0);
 		__block_commit_write(inode, new_page,
 				zerofrom, PAGE_CACHE_SIZE);
-		kunmap(new_page);
 		unlock_page(new_page);
 		page_cache_release(new_page);
 	}

@@ -2135,21 +2145,20 @@ int cont_prepare_write(struct page *page
 	status = __block_prepare_write(inode, page, zerofrom, to, get_block);
 	if (status)
 		goto out1;
-	kaddr = page_address(page);
 	if (zerofrom < offset) {
+		kaddr = kmap_atomic(page, KM_USER0);
 		memset(kaddr+zerofrom, 0, offset-zerofrom);
 		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
 		__block_commit_write(inode, page, zerofrom, offset);
 	}
 	return 0;

out1:

	ClearPageUptodate(page);

fs/buffer.c renamed from fs/buffer.c~kmap_atomic_writes +0 -1

-	kunmap(page);

	return status;

out_unmap:

	ClearPageUptodate(new_page);

fs/buffer.c renamed from fs/buffer.c~kmap_atomic_writes +0 -1

-	kunmap(new_page);

	unlock_page(new_page);
	page_cache_release(new_page);

out:

fs/buffer.c renamed from fs/buffer.c~kmap_atomic_writes +8 -10

@@ -2161,10 +2170,8 @@ int block_prepare_write(struct page *pag
 {
 	struct inode *inode = page->mapping->host;
 	int err = __block_prepare_write(inode, page, from, to, get_block);
-	if (err) {
+	if (err)
 		ClearPageUptodate(page);
-		kunmap(page);
-	}
 	return err;
 }
 

@@ -2172,7 +2179,6 @@ int block_commit_write(struct page *page
 {
 	struct inode *inode = page->mapping->host;
 	__block_commit_write(inode,page,from,to);
-	kunmap(page);
 	return 0;
 }
 

@@ -2182,7 +2188,6 @@ int generic_commit_write(struct file *fi
 	struct inode *inode = page->mapping->host;
 	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 	__block_commit_write(inode,page,from,to);
-	kunmap(page);
 	if (pos > inode->i_size) {
 		inode->i_size = pos;
 		mark_inode_dirty(inode);

@@ -2199,6 +2204,7 @@ int block_truncate_page(struct address_s
 	struct inode *inode = mapping->host;
 	struct page *page;
 	struct buffer_head *bh;
+	void *kaddr;
 	int err;
 
 	blocksize = 1 << inode->i_blkbits;

@@ -2251,9 +2257,10 @@ int block_truncate_page(struct address_s
 			goto unlock;
 	}
 
-	memset(kmap(page) + offset, 0, length);
+	kaddr = kmap_atomic(page, KM_USER0);
+	memset(kaddr + offset, 0, length);
 	flush_dcache_page(page);
-	kunmap(page);
+	kunmap_atomic(kaddr, KM_USER0);
 
 	mark_buffer_dirty(bh);
 	err = 0;

@@ -2273,7 +2280,7 @@ int block_write_full_page(struct page *p
 	struct inode * const inode = page->mapping->host;
 	const unsigned long end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 	unsigned offset;
-	char *kaddr;
+	void *kaddr;
 
 	/* Is the page fully inside i_size? */
 	if (page->index < end_index)

@@ -2293,10 +2300,10 @@ int block_write_full_page(struct page *p
 	 * the  page size, the remaining memory is zeroed when mapped, and
 	 * writes to that region are not written out to the file."
 	 */
-	kaddr = kmap(page);
+	kaddr = kmap_atomic(page, KM_USER0);
 	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
 	flush_dcache_page(page);
-	kunmap(page);
+	kunmap_atomic(page, KM_USER0);
 	return __block_write_full_page(inode, page, get_block);
 }
 

fs/ext3/inode.c renamed from fs/ext3/inode.c~kmap_atomic_writes +0 -10

@@ -1048,16 +1048,6 @@ static int ext3_prepare_write(struct fil
 	if (ext3_should_journal_data(inode)) {
 		ret = walk_page_buffers(handle, page_buffers(page),
 				from, to, NULL, do_journal_get_write_access);
-		if (ret) {
-			/*
-			 * We're going to fail this prepare_write(),
-			 * so commit_write() will not be called.
-			 * We need to undo block_prepare_write()'s kmap().
-			 * AKPM: Do we need to clear PageUptodate?  I don't
-			 * think so.
-			 */
-			kunmap(page);
-		}
 	}

prepare_write_failed:
if (ret)

fs/ext3/inode.c renamed from fs/ext3/inode.c~kmap_atomic_writes +6 -14

@@ -1117,7 +1107,6 @@ static int ext3_commit_write(struct file
 			from, to, &partial, commit_write_fn);
 		if (!partial)
 			SetPageUptodate(page);
-		kunmap(page);
 		if (pos > inode->i_size)
 			inode->i_size = pos;
 		EXT3_I(inode)->i_state |= EXT3_STATE_JDATA;

@@ -1128,17 +1117,8 @@ static int ext3_commit_write(struct file
 		}
 		/* Be careful here if generic_commit_write becomes a
 		 * required invocation after block_prepare_write. */
-		if (ret == 0) {
+		if (ret == 0)
 			ret = generic_commit_write(file, page, from, to);
-		} else {
-			/*
-			 * block_prepare_write() was called, but we're not
-			 * going to call generic_commit_write().  So we
-			 * need to perform generic_commit_write()'s kunmap
-			 * by hand.
-			 */
-			kunmap(page);
-		}
 	}
 	if (inode->i_size > EXT3_I(inode)->i_disksize) {
 		EXT3_I(inode)->i_disksize = inode->i_size;

@@ -1433,6 +1413,7 @@ static int ext3_block_truncate_page(hand
 	struct page *page;
 	struct buffer_head *bh;
 	int err;
+	void *kaddr;
 
 	blocksize = inode->i_sb->s_blocksize;
 	length = offset & (blocksize - 1);

@@ -1488,10 +1469,11 @@ static int ext3_block_truncate_page(hand
 		if (err)
 			goto unlock;
 	}
-	
-	memset(kmap(page) + offset, 0, length);
+
+	kaddr = kmap_atomic(page, KM_USER0);
+	memset(kaddr + offset, 0, length);
 	flush_dcache_page(page);
-	kunmap(page);
+	kunmap_atomic(kaddr, KM_USER0);
 
 	BUFFER_TRACE(bh, "zeroed end of block");
 

fs/ext2/dir.c renamed from fs/ext2/dir.c~kmap_atomic_writes +5 -6

@@ -571,8 +571,8 @@ int ext2_make_empty(struct inode *inode,
 	struct page *page = grab_cache_page(mapping, 0);
 	unsigned chunk_size = ext2_chunk_size(inode);
 	struct ext2_dir_entry_2 * de;
-	char *base;
 	int err;
+	void *kaddr;
 
 	if (!page)
 		return -ENOMEM;

@@ -581,22 +581,21 @@ int ext2_make_empty(struct inode *inode,
 		unlock_page(page);
 		goto fail;
 	}
-	base = page_address(page);
-
-	de = (struct ext2_dir_entry_2 *) base;
+	kaddr = kmap_atomic(page, KM_USER0);
+	de = (struct ext2_dir_entry_2 *)kaddr;
 	de->name_len = 1;
 	de->rec_len = cpu_to_le16(EXT2_DIR_REC_LEN(1));
 	memcpy (de->name, ".\0\0", 4);
 	de->inode = cpu_to_le32(inode->i_ino);
 	ext2_set_de_type (de, inode);
 
-	de = (struct ext2_dir_entry_2 *) (base + EXT2_DIR_REC_LEN(1));
+	de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
 	de->name_len = 2;
 	de->rec_len = cpu_to_le16(chunk_size - EXT2_DIR_REC_LEN(1));
 	de->inode = cpu_to_le32(parent->i_ino);
 	memcpy (de->name, "..\0", 4);
 	ext2_set_de_type (de, inode);
-
+	kunmap_atomic(kaddr, KM_USER0);
 	err = ext2_commit_chunk(page, 0, chunk_size);

fail:

	page_cache_release(page);

fs/namei.c renamed from fs/namei.c~kmap_atomic_writes +2 -1

@@ -2200,8 +2200,9 @@ int page_symlink(struct inode *inode, co
 	err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
 	if (err)
 		goto fail_map;
-	kaddr = page_address(page);
+	kaddr = kmap_atomic(page, KM_USER0);
 	memcpy(kaddr, symname, len-1);
+	kunmap_atomic(kaddr, KM_USER0);
 	mapping->a_ops->commit_write(NULL, page, 0, len-1);
 	/*
 	 * Notice that we are _not_ going to block here - end of page is

drivers/block/loop.c renamed from drivers/block/loop.c~kmap_atomic_writes +3 -2

@@ -210,8 +210,7 @@ do_lo_send(struct loop_device *lo, struc
 			goto fail;
 		if (aops->prepare_write(file, page, offset, offset+size))
 			goto unlock;
-		kaddr = page_address(page);
-		flush_dcache_page(page);
+		kaddr = kmap(page);
 		transfer_result = lo_do_transfer(lo, WRITE, kaddr + offset, data, size, IV);
 		if (transfer_result) {
 			/*

@@ -221,6 +220,8 @@ do_lo_send(struct loop_device *lo, struc
 			printk(KERN_ERR "loop: transfer error block %ld\n", index);
 			memset(kaddr + offset, 0, size);
 		}
+		flush_dcache_page(page);
+		kunmap(page);
 		if (aops->commit_write(file, page, offset, offset+size))
 			goto unlock;
 		if (transfer_result)

drivers/block/rd.c renamed from drivers/block/rd.c~kmap_atomic_writes +13 -6

@@ -109,9 +109,11 @@ int rd_blocksize = BLOCK_SIZE;			/* bloc
 static int ramdisk_readpage(struct file *file, struct page * page)
 {
 	if (!PageUptodate(page)) {
-		memset(kmap(page), 0, PAGE_CACHE_SIZE);
-		kunmap(page);
+		void *kaddr = kmap_atomic(page, KM_USER0);
+
+		memset(kaddr, 0, PAGE_CACHE_SIZE);
 		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
 		SetPageUptodate(page);
 	}
 	unlock_page(page);

@@ -121,9 +123,11 @@ static int ramdisk_readpage(struct file 
 static int ramdisk_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
 {
 	if (!PageUptodate(page)) {
-		void *addr = page_address(page);
-		memset(addr, 0, PAGE_CACHE_SIZE);
+		void *kaddr = kmap_atomic(page, KM_USER0);
+
+		memset(kaddr, 0, PAGE_CACHE_SIZE);
 		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
 		SetPageUptodate(page);
 	}
 	SetPageDirty(page);

@@ -178,8 +182,11 @@ static int rd_blkdev_pagecache_IO(int rw
 			err = 0;
 
 			if (!PageUptodate(page)) {
-				memset(kmap(page), 0, PAGE_CACHE_SIZE);
-				kunmap(page);
+				void *kaddr = kmap_atomic(page, KM_USER0);
+
+				memset(kaddr, 0, PAGE_CACHE_SIZE);
+				flush_dcache_page(page);
+				kunmap_atomic(kaddr, KM_USER0);
 				SetPageUptodate(page);
 			}
 

fs/affs/file.c renamed from fs/affs/file.c~kmap_atomic_writes +10 -1

@@ -27,6 +27,7 @@
 #include <linux/fs.h>
 #include <linux/amigaffs.h>
 #include <linux/mm.h>
+#include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <linux/buffer_head.h>
 

@@ -518,6 +519,7 @@ affs_do_readpage_ofs(struct file *file, 
 	pr_debug("AFFS: read_page(%u, %ld, %d, %d)\n", (u32)inode->i_ino, page->index, from, to);
 	if (from > to || to > PAGE_CACHE_SIZE)
 		BUG();
+	kmap(page);
 	data = page_address(page);
 	bsize = AFFS_SB(sb)->s_data_blksize;
 	tmp = (page->index << PAGE_CACHE_SHIFT) + from;

@@ -532,11 +534,14 @@ affs_do_readpage_ofs(struct file *file, 
 		if (from + tmp > to || tmp > bsize)
 			BUG();
 		memcpy(data + from, AFFS_DATA(bh) + boff, tmp);
+		flush_dcache_page(page);
 		affs_brelse(bh);
 		bidx++;
 		from += tmp;
 		boff = 0;
 	}
+	flush_dcache_page(page);
+	kunmap(page);
 	return 0;
 }
 

@@ -656,7 +661,11 @@ static int affs_prepare_write_ofs(struct
 			return err;
 	}
 	if (to < PAGE_CACHE_SIZE) {
-		memset(page_address(page) + to, 0, PAGE_CACHE_SIZE - to);
+		char *kaddr = kmap_atomic(page, KM_USER0);
+
+		memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
+		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
 		if (size > offset + to) {
 			if (size < offset + PAGE_CACHE_SIZE)
 				tmp = size & ~PAGE_CACHE_MASK;

fs/driverfs/inode.c renamed from fs/driverfs/inode.c~kmap_atomic_writes +3 -3

@@ -71,10 +71,11 @@ static int driverfs_readpage(struct file
 
 static int driverfs_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
 {
-	void *addr = kmap(page);
 	if (!PageUptodate(page)) {
-		memset(addr, 0, PAGE_CACHE_SIZE);
+		void *kaddr = kmap_atomic(page, KM_USER0);
+		memset(kaddr, 0, PAGE_CACHE_SIZE);
 		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
 		SetPageUptodate(page);
 	}
 	return 0;

@@ -86,7 +87,6 @@ static int driverfs_commit_write(struct 
 	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 
 	set_page_dirty(page);
-	kunmap(page);
 	if (pos > inode->i_size)
 		inode->i_size = pos;
 	return 0;

fs/jffs/inode-v23.c renamed from fs/jffs/inode-v23.c~kmap_atomic_writes +7 -4

@@ -47,6 +47,7 @@
 #include <linux/stat.h>
 #include <linux/blkdev.h>
 #include <linux/quotaops.h>
+#include <linux/highmem.h>
 #include <linux/smp_lock.h>
 #include <asm/semaphore.h>
 #include <asm/byteorder.h>

@@ -751,7 +752,6 @@ jffs_do_readpage_nolock(struct file *fil
 
 	get_page(page);
 	/* Don't SetPageLocked(page), should be locked already */
-	buf = page_address(page);
 	ClearPageUptodate(page);
 	ClearPageError(page);
 

@@ -760,8 +760,10 @@ jffs_do_readpage_nolock(struct file *fil
 
 	read_len = 0;
 	result = 0;
-
 	offset = page->index << PAGE_CACHE_SHIFT;
+
+	kmap(page);
+	buf = page_address(page);
 	if (offset < inode->i_size) {
 		read_len = min_t(long, inode->i_size - offset, PAGE_SIZE);
 		r = jffs_read_data(f, buf, offset, read_len);

@@ -779,6 +781,8 @@ jffs_do_readpage_nolock(struct file *fil
 	/* This handles the case of partial or no read in above */
 	if(read_len < PAGE_SIZE)
 	        memset(buf + read_len, 0, PAGE_SIZE - read_len);
+	flush_dcache_page(page);
+	kunmap(page);
 
 	D3(printk (KERN_NOTICE "readpage(): up biglock\n"));
 	up(&c->fmc->biglock);

@@ -788,9 +792,8 @@ jffs_do_readpage_nolock(struct file *fil
 	}else {
 	        SetPageUptodate(page);	        
 	}
-	flush_dcache_page(page);
 
-	put_page(page);
+	page_cache_release(page);
 
 	D3(printk("jffs_readpage(): Leaving...\n"));
 

fs/jffs2/file.c renamed from fs/jffs2/file.c~kmap_atomic_writes +3 -1

@@ -17,6 +17,7 @@
 #include <linux/fs.h>
 #include <linux/time.h>
 #include <linux/pagemap.h>
+#include <linux/highmem.h>
 #include <linux/crc32.h>
 #include <linux/jffs2.h>
 #include "nodelist.h"

@@ -381,9 +382,10 @@ int jffs2_commit_write (struct file *fil
 	ri->isize = (uint32_t)inode->i_size;
 	ri->atime = ri->ctime = ri->mtime = CURRENT_TIME;
 
-	/* We rely on the fact that generic_file_write() currently kmaps the page for us. */
+	kmap(pg);
 	ret = jffs2_write_inode_range(c, f, ri, page_address(pg) + start,
 				      (pg->index << PAGE_CACHE_SHIFT) + start, end - start, &writtenlen);
+	kunmap(pg);
 
 	if (ret) {
 		/* There was an error writing. */

fs/jfs/jfs_metapage.c renamed from fs/jfs/jfs_metapage.c~kmap_atomic_writes +0 -1

@@ -467,7 +467,6 @@ static void __write_metapage(metapage_t 
 	if (rc) {
 		jERROR(1, ("prepare_write return %d!\n", rc));
 		ClearPageUptodate(mp->page);
-		kunmap(mp->page);
 		unlock_page(mp->page);
 		clear_bit(META_dirty, &mp->flag);
 		return;

fs/minix/dir.c renamed from fs/minix/dir.c~kmap_atomic_writes +7 -5

@@ -7,6 +7,7 @@
 */
 
 #include "minix.h"
+#include <linux/highmem.h>
 #include <linux/smp_lock.h>
 
 typedef struct minix_dir_entry minix_dirent;

@@ -261,7 +262,7 @@ int minix_delete_entry(struct minix_dir_
 {
 	struct address_space *mapping = page->mapping;
 	struct inode *inode = (struct inode*)mapping->host;
-	char *kaddr = (char*)page_address(page);
+	char *kaddr = page_address(page);
 	unsigned from = (char*)de - kaddr;
 	unsigned to = from + minix_sb(inode->i_sb)->s_dirsize;
 	int err;

@@ -286,7 +287,7 @@ int minix_make_empty(struct inode *inode
 	struct page *page = grab_cache_page(mapping, 0);
 	struct minix_sb_info * sbi = minix_sb(inode->i_sb);
 	struct minix_dir_entry * de;
-	char *base;
+	char *kaddr;
 	int err;
 
 	if (!page)

@@ -297,15 +298,16 @@ int minix_make_empty(struct inode *inode
 		goto fail;
 	}
 
-	base = (char*)page_address(page);
-	memset(base, 0, PAGE_CACHE_SIZE);
+	kaddr = kmap_atomic(page, KM_USER0);
+	memset(kaddr, 0, PAGE_CACHE_SIZE);
 
-	de = (struct minix_dir_entry *) base;
+	de = (struct minix_dir_entry *)kaddr;
 	de->inode = inode->i_ino;
 	strcpy(de->name,".");
 	de = minix_next_entry(de, sbi);
 	de->inode = dir->i_ino;
 	strcpy(de->name,"..");
+	kunmap_atomic(kaddr, KM_USER0);
 
 	err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);

fail:

fs/ramfs/inode.c renamed from fs/ramfs/inode.c~kmap_atomic_writes +9 -5

@@ -26,6 +26,7 @@
 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
+#include <linux/highmem.h>
 #include <linux/init.h>
 #include <linux/string.h>
 #include <linux/smp_lock.h>

@@ -47,8 +48,10 @@ static struct inode_operations ramfs_dir
 static int ramfs_readpage(struct file *file, struct page * page)
 {
 	if (!PageUptodate(page)) {
-		memset(kmap(page), 0, PAGE_CACHE_SIZE);
-		kunmap(page);
+		char *kaddr = kmap_atomic(page, KM_USER0);
+
+		memset(kaddr, 0, PAGE_CACHE_SIZE);
+		kunmap_atomic(kaddr, KM_USER0);
 		flush_dcache_page(page);
 		SetPageUptodate(page);
 	}

@@ -58,10 +61,12 @@ static int ramfs_readpage(struct file *f
 
 static int ramfs_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
 {
-	void *addr = kmap(page);
 	if (!PageUptodate(page)) {
-		memset(addr, 0, PAGE_CACHE_SIZE);
+		char *kaddr = kmap_atomic(page, KM_USER0);
+
+		memset(kaddr, 0, PAGE_CACHE_SIZE);
 		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
 		SetPageUptodate(page);
 	}
 	SetPageDirty(page);

@@ -73,7 +78,6 @@ static int ramfs_commit_write(struct fil
 	struct inode *inode = page->mapping->host;
 	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
 
-	kunmap(page);
 	if (pos > inode->i_size)
 		inode->i_size = pos;
 	return 0;

fs/reiserfs/inode.c renamed from fs/reiserfs/inode.c~kmap_atomic_writes +19 -8

@@ -7,6 +7,7 @@
 #include <linux/reiserfs_fs.h>
 #include <linux/smp_lock.h>
 #include <linux/pagemap.h>
+#include <linux/highmem.h>
 #include <asm/uaccess.h>
 #include <asm/unaligned.h>
 #include <linux/buffer_head.h>

@@ -485,8 +486,10 @@ static int convert_tail_for_hole(struct 
    ** won't trigger a get_block in this case.
    */
    fix_tail_page_for_writing(tail_page) ;
+    kmap(tail_page);
    retval = block_prepare_write(tail_page, tail_start, tail_end, 
                                 reiserfs_get_block) ; 
+    kunmap(tail_page);
    if (retval)
        goto unlock ;
 

@@ -1687,12 +1690,13 @@ static int grab_tail_page(struct inode *
    /* start within the page of the last block in the file */
    start = (offset / blocksize) * blocksize ;
 
+    kmap(page);
    error = block_prepare_write(page, start, offset, 
 				reiserfs_get_block_create_0) ;
    if (error)
 	goto unlock ;
 
-    kunmap(page) ; /* mapped by block_prepare_write */
+    kunmap(page) ;
 
    head = page_buffers(page) ;      
    bh = head;

@@ -1788,10 +1792,13 @@ void reiserfs_truncate_file(struct inode
        length = offset & (blocksize - 1) ;
 	/* if we are not on a block boundary */
 	if (length) {
+	    char *kaddr;
+
 	    length = blocksize - length ;
-	    memset((char *)kmap(page) + offset, 0, length) ;   
+	    kaddr = kmap_atomic(page, KM_USER0) ;
+	    memset(kaddr + offset, 0, length) ;   
 	    flush_dcache_page(page) ;
-	    kunmap(page) ;
+	    kunmap_atomic(kaddr, KM_USER0) ;
 	    if (buffer_mapped(bh) && bh->b_blocknr != 0) {
 	        mark_buffer_dirty(bh) ;
 	    }

@@ -1941,23 +1948,25 @@ static int reiserfs_write_full_page(stru
    struct buffer_head *arr[PAGE_CACHE_SIZE/512] ;
    int nr = 0 ;
 
-    if (!page_has_buffers(page)) {
+    if (!page_has_buffers(page))
        block_prepare_write(page, 0, 0, NULL) ;
-	kunmap(page) ;
-    }
+
    /* last page in the file, zero out any contents past the
    ** last byte in the file
    */
    if (page->index >= end_index) {
+	char *kaddr;
+
        last_offset = inode->i_size & (PAGE_CACHE_SIZE - 1) ;
 	/* no file contents in this page */
 	if (page->index >= end_index + 1 || !last_offset) {
 	    error =  -EIO ;
 	    goto fail ;
 	}
-	memset((char *)kmap(page)+last_offset, 0, PAGE_CACHE_SIZE-last_offset) ;
+	kaddr = kmap_atomic(page, KM_USER0);
+	memset(kaddr + last_offset, 0, PAGE_CACHE_SIZE-last_offset) ;
 	flush_dcache_page(page) ;
-	kunmap(page) ;
+	kunmap_atomic(kaddr, KM_USER0) ;
    }
    head = page_buffers(page) ;
    bh = head ;

@@ -2040,6 +2049,7 @@ int reiserfs_prepare_write(struct file *
 			   unsigned from, unsigned to) {
    struct inode *inode = page->mapping->host ;
    reiserfs_wait_on_write_block(inode->i_sb) ;
+    kmap(page);
    fix_tail_page_for_writing(page) ;
    return block_prepare_write(page, from, to, reiserfs_get_block) ;
 }

@@ -2082,6 +2092,7 @@ static int reiserfs_commit_write(struct 
 	reiserfs_commit_for_inode(inode) ;
 	reiserfs_write_unlock(inode->i_sb);
    }
+    kunmap(page);
    return ret ;
 }
 

fs/sysv/dir.c renamed from fs/sysv/dir.c~kmap_atomic_writes +2 -0

@@ -14,6 +14,7 @@
 */
 
 #include <linux/pagemap.h>
+#include <linux/highmem.h>
 #include <linux/smp_lock.h>
 #include "sysv.h"
 

@@ -273,6 +274,7 @@ int sysv_make_empty(struct inode *inode,
 
 	if (!page)
 		return -ENOMEM;
+	kmap(page);
 	err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * SYSV_DIRSIZE);
 	if (err) {
 		unlock_page(page);

@@ -291,6 +293,7 @@ int sysv_make_empty(struct inode *inode,
 
 	err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);

fail:

fs/sysv/dir.c renamed from fs/sysv/dir.c~kmap_atomic_writes +1 -0

+	kunmap(page);

	page_cache_release(page);
	return err;
}

fs/fat/inode.c renamed from fs/fat/inode.c~kmap_atomic_writes +15 -2

@@ -982,11 +982,24 @@ static int fat_readpage(struct file *fil
 {
 	return block_read_full_page(page,fat_get_block);
 }
-static int fat_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to)
+
+static int
+fat_prepare_write(struct file *file, struct page *page,
+			unsigned from, unsigned to)
 {
+	kmap(page);
 	return cont_prepare_write(page,from,to,fat_get_block,
 		&MSDOS_I(page->mapping->host)->mmu_private);
 }
+
+static int
+fat_commit_write(struct file *file, struct page *page,
+			unsigned from, unsigned to)
+{
+	kunmap(page);
+	return generic_commit_write(file, page, from, to);
+}
+
 static int _fat_bmap(struct address_space *mapping, long block)
 {
 	return generic_block_bmap(mapping,block,fat_get_block);

@@ -996,7 +1009,7 @@ static struct address_space_operations f
 	writepage: fat_writepage,
 	sync_page: block_sync_page,
 	prepare_write: fat_prepare_write,
-	commit_write: generic_commit_write,
+	commit_write: fat_commit_write,
 	bmap: _fat_bmap
 };
 

.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

I made a bit of a mess of reiserfs. It works OK, but I suspect it's performing unnecessary kmaps.

Hello!

Quoted 2 lines · Andrew Morton

I made a bit of a mess of reiserfs. It works OK, but I suspect it's performing unnecessary kmaps.

We have reviewed the fs/reiserfs/inode.c change you proposed and we think that patch below should be applied instead of it.

Unfortunatelly we were not able to test it as 2.5.30 + your patches locks up even before it have a chance to go to login prompt (and to even touch reiserfs code, since I was booting off ext2 partition).

Quoted 6 lines · Oleg Drokin

Hello!

On Fri, Aug 09, 2002 at 05:57:12PM -0700, Andrew Morton wrote:

Quoted 8 lines

Quoted 4 lines

I made a bit of a mess of reiserfs. It works OK, but I suspect it's performing unnecessary kmaps.

We have reviewed the fs/reiserfs/inode.c change you proposed and we think that patch below should be applied instead of it.

OK, thanks - shall do.

Quoted 5 lines

Unfortunatelly we were not able to test it as 2.5.30 + your patches locks up even before it have a chance to go to login prompt (and to even touch reiserfs code, since I was booting off ext2 partition).

That's strange - that code has been under test by myself and several others for a week or two.