O_SYNC patch 3/3, add inode dirty buffer list support to ext2

Hi,

This final part of the O_SYNC patches adds calls to ext2, and to generic_commit_write, to record dirty buffers against the owning inode. It also removes most of fs/ext2/fsync.c, which now simply calls the generic sync code.

--Stephen

2.4.0test11.02.ext2-osync.diff :

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

@@ -1727,6 +1727,7 @@
 			set_bit(BH_Uptodate, &bh->b_state);
 			if (!atomic_set_buffer_dirty(bh)) {
 				__mark_dirty(bh);
+				buffer_insert_inode_queue(bh, inode);
 				need_balance_dirty = 1;
 			}
 		}

fs/ext2/fsync.c renamed from fs/ext2/fsync.c.~1~ +13 -119

@@ -28,98 +28,6 @@
 #include <linux/smp_lock.h>
 
 
-#define blocksize	(EXT2_BLOCK_SIZE(inode->i_sb))
-#define addr_per_block	(EXT2_ADDR_PER_BLOCK(inode->i_sb))
-
-static int sync_indirect(struct inode * inode, u32 * block, int wait)
-{
-	struct buffer_head * bh;
-	
-	if (!*block)
-		return 0;
-	bh = get_hash_table(inode->i_dev, le32_to_cpu(*block), blocksize);
-	if (!bh)
-		return 0;
-	if (wait && buffer_req(bh) && !buffer_uptodate(bh)) {
-		/* There can be a parallell read(2) that started read-I/O
-		   on the buffer so we can't assume that there's been
-		   an I/O error without first waiting I/O completation. */
-		wait_on_buffer(bh);
-		if (!buffer_uptodate(bh))
-		{
-			brelse (bh);
-			return -1;
-		}
-	}
-	if (wait || !buffer_uptodate(bh) || !buffer_dirty(bh)) {
-		if (wait)
-			/* when we return from fsync all the blocks
-			   must be _just_ stored on disk */
-			wait_on_buffer(bh);
-		brelse(bh);
-		return 0;
-	}
-	ll_rw_block(WRITE, 1, &bh);
-	atomic_dec(&bh->b_count);
-	return 0;
-}
-
-static int sync_iblock(struct inode * inode, u32 * iblock, 
-			struct buffer_head ** bh, int wait) 
-{
-	int rc, tmp;
-	
-	*bh = NULL;
-	tmp = le32_to_cpu(*iblock);
-	if (!tmp)
-		return 0;
-	rc = sync_indirect(inode, iblock, wait);
-	if (rc)
-		return rc;
-	*bh = bread(inode->i_dev, tmp, blocksize);
-	if (!*bh)
-		return -1;
-	return 0;
-}
-
-static int sync_dindirect(struct inode * inode, u32 * diblock, int wait)
-{
-	int i;
-	struct buffer_head * dind_bh;
-	int rc, err = 0;
-
-	rc = sync_iblock(inode, diblock, &dind_bh, wait);
-	if (rc || !dind_bh)
-		return rc;
-	
-	for (i = 0; i < addr_per_block; i++) {
-		rc = sync_indirect(inode, ((u32 *) dind_bh->b_data) + i, wait);
-		if (rc)
-			err = rc;
-	}
-	brelse(dind_bh);
-	return err;
-}
-
-static int sync_tindirect(struct inode * inode, u32 * tiblock, int wait)
-{
-	int i;
-	struct buffer_head * tind_bh;
-	int rc, err = 0;
-
-	rc = sync_iblock(inode, tiblock, &tind_bh, wait);
-	if (rc || !tind_bh)
-		return rc;
-	
-	for (i = 0; i < addr_per_block; i++) {
-		rc = sync_dindirect(inode, ((u32 *) tind_bh->b_data) + i, wait);
-		if (rc)
-			err = rc;
-	}
-	brelse(tind_bh);
-	return err;
-}
-
 /*
  *	File may be NULL when we are called. Perhaps we shouldn't
  *	even pass file to fsync ?

@@ -127,34 +35,20 @@
 
 int ext2_sync_file(struct file * file, struct dentry *dentry, int datasync)
 {
-	int wait, err = 0;
 	struct inode *inode = dentry->d_inode;
+	return ext2_fsync_inode(inode, datasync);
+}
 
-	lock_kernel();
-	if (S_ISLNK(inode->i_mode) && !(inode->i_blocks))
-		/*
-		 * Don't sync fast links!
-		 */
-		goto skip;
-
-	err = generic_buffer_fdatasync(inode, 0, ~0UL);
-
-	for (wait=0; wait<=1; wait++)
-	{
-		err |= sync_indirect(inode,
-				     inode->u.ext2_i.i_data+EXT2_IND_BLOCK,
-				     wait);
-		err |= sync_dindirect(inode,
-				      inode->u.ext2_i.i_data+EXT2_DIND_BLOCK, 
-				      wait);
-		err |= sync_tindirect(inode, 
-				      inode->u.ext2_i.i_data+EXT2_TIND_BLOCK, 
-				      wait);
-	}
-skip:
-	if ((inode->i_state & I_DIRTY_DATASYNC) || 
-	    ((inode->i_state & I_DIRTY) && !datasync))
-		err |= ext2_sync_inode (inode);
-	unlock_kernel();
+int ext2_fsync_inode(struct inode *inode, int datasync)
+{
+	int err;
+	
+	err  = fsync_inode_buffers(inode);
+	if (!(inode->i_state & I_DIRTY))
+		return err;
+	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
+		return err;
+	
+	err |= ext2_sync_inode(inode);
 	return err ? -EIO : 0;
 }

fs/ext2/inode.c renamed from fs/ext2/inode.c.~1~ +6 -6

@@ -404,7 +404,7 @@
 		branch[n].p = (u32*) bh->b_data + offsets[n];
 		*branch[n].p = branch[n].key;
 		mark_buffer_uptodate(bh, 1);
-		mark_buffer_dirty(bh);
+		mark_buffer_dirty_inode(bh, inode);
 		if (IS_SYNC(inode) || inode->u.ext2_i.i_osync) {
 			ll_rw_block (WRITE, 1, &bh);
 			wait_on_buffer (bh);

@@ -469,7 +469,7 @@
 
 	/* had we spliced it onto indirect block? */
 	if (where->bh) {
-		mark_buffer_dirty(where->bh);
+		mark_buffer_dirty_inode(where->bh, inode);
 		if (IS_SYNC(inode) || inode->u.ext2_i.i_osync) {
 			ll_rw_block (WRITE, 1, &where->bh);
 			wait_on_buffer(where->bh);

@@ -591,7 +591,7 @@
 				wait_on_buffer(bh);
 			memset(bh->b_data, 0, inode->i_sb->s_blocksize);
 			mark_buffer_uptodate(bh, 1);
-			mark_buffer_dirty(bh);
+			mark_buffer_dirty_inode(bh, inode);
 		}
 		return bh;
 	}

@@ -907,7 +907,7 @@
 		if (partial == chain)
 			mark_inode_dirty(inode);
 		else
-			mark_buffer_dirty(partial->bh);
+			mark_buffer_dirty_inode(partial->bh, inode);
 		ext2_free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
 	}
 	/* Clear the ends of indirect blocks on the shared branch */

@@ -916,7 +916,7 @@
 				   partial->p + 1,
 				   (u32*)partial->bh->b_data + addr_per_block,
 				   (chain+n-1) - partial);
-		mark_buffer_dirty(partial->bh);
+		mark_buffer_dirty_inode(partial->bh, inode);
 		if (IS_SYNC(inode)) {
 			ll_rw_block (WRITE, 1, &partial->bh);
 			wait_on_buffer (partial->bh);

@@ -1208,7 +1208,7 @@
 		raw_inode->i_block[0] = cpu_to_le32(kdev_t_to_nr(inode->i_rdev));
 	else for (block = 0; block < EXT2_N_BLOCKS; block++)
 		raw_inode->i_block[block] = inode->u.ext2_i.i_data[block];
-	mark_buffer_dirty(bh);
+	mark_buffer_dirty_inode(bh, inode);
 	if (do_sync) {
 		ll_rw_block (WRITE, 1, &bh);
 		wait_on_buffer (bh);

fs/ext2/namei.c renamed from fs/ext2/namei.c.~1~ +5 -5

@@ -296,7 +296,7 @@
 			dir->u.ext2_i.i_flags &= ~EXT2_BTREE_FL;
 			mark_inode_dirty(dir);
 			dir->i_version = ++event;
-			mark_buffer_dirty(bh);
+			mark_buffer_dirty_inode(bh, dir);
 			if (IS_SYNC(dir)) {
 				ll_rw_block (WRITE, 1, &bh);
 				wait_on_buffer (bh);

@@ -337,7 +337,7 @@
 			else
 				de->inode = 0;
 			dir->i_version = ++event;
-			mark_buffer_dirty(bh);
+			mark_buffer_dirty_inode(bh, dir);
 			if (IS_SYNC(dir)) {
 				ll_rw_block (WRITE, 1, &bh);
 				wait_on_buffer (bh);

@@ -449,7 +449,7 @@
 	strcpy (de->name, "..");
 	ext2_set_de_type(dir->i_sb, de, S_IFDIR);
 	inode->i_nlink = 2;
-	mark_buffer_dirty(dir_block);
+	mark_buffer_dirty_inode(dir_block, dir);
 	brelse (dir_block);
 	inode->i_mode = S_IFDIR | mode;
 	if (dir->i_mode & S_ISGID)

@@ -755,7 +755,7 @@
 					      EXT2_FEATURE_INCOMPAT_FILETYPE))
 			new_de->file_type = old_de->file_type;
 		new_dir->i_version = ++event;
-		mark_buffer_dirty(new_bh);
+		mark_buffer_dirty_inode(new_bh, new_dir);
 		if (IS_SYNC(new_dir)) {
 			ll_rw_block (WRITE, 1, &new_bh);
 			wait_on_buffer (new_bh);

@@ -786,7 +786,7 @@
 	mark_inode_dirty(old_dir);
 	if (dir_bh) {
 		PARENT_INO(dir_bh->b_data) = le32_to_cpu(new_dir->i_ino);
-		mark_buffer_dirty(dir_bh);
+		mark_buffer_dirty_inode(dir_bh, old_inode);
 		old_dir->i_nlink--;
 		mark_inode_dirty(old_dir);
 		if (new_inode) {

include/linux/ext2_fs.h renamed from include/linux/ext2_fs.h.~1~ +1 -0

@@ -549,6 +549,7 @@
 
 /* fsync.c */
 extern int ext2_sync_file (struct file *, struct dentry *, int);
+extern int ext2_fsync_inode (struct inode *, int);
 
 /* ialloc.c */
 extern struct inode * ext2_new_inode (const struct inode *, int, int *);

mm/filemap.c renamed from mm/filemap.c.~1~ +6 -1

@@ -2521,8 +2521,14 @@
 	if (cached_page)
 		page_cache_free(cached_page);
 
+	/* For now, when the user asks for O_SYNC, we'll actually
+	 * provide O_DSYNC. */
+	if ((status >= 0) && (file->f_flags & O_SYNC))
+		status = generic_osync_inode(inode, 1); /* 1 means datasync */
+	
 	err = written ? written : status;
 out:
+
 	up(&inode->i_sem);
 	return err;
 fail_write:
-

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Quoted 3 lines

Is this assumption correct, and does this comply with TPC rules for ORACLE and other DBMS benchmarks? It looks like a good patch that will perform very fast for O_SYNC.

Quoted 8 lines · Stephen C. Tweedie

Hi,

This final part of the O_SYNC patches adds calls to ext2, and to generic_commit_write, to record dirty buffers against the owning inode. It also removes most of fs/ext2/fsync.c, which now simply calls the generic sync code.

--Stephen

Stephen,

I have not implemented O_SYNC in NWFS, but it looks like I need to add it before posting the final patches. This patch appears to force write-through of only dirty inodes, and allow reads to continue from cache. Is this assumption correct, and does this comply with TPC rules for ORACLE and other DBMS benchmarks? It looks like a good patch that will perform very fast for O_SYNC.

Jeff

Quoted 293 lines

2.4.0test11.02.ext2-osync.diff :

fs/buffer.c Tue Nov 21 16:35:35 2000 renamed from fs/buffer.c.~1~ Tue Nov 21 15:51:17 2000 +1 -0

@@ -1727,6 +1727,7 @@
                      set_bit(BH_Uptodate, &bh->b_state);
                      if (!atomic_set_buffer_dirty(bh)) {
                              __mark_dirty(bh);
+                             buffer_insert_inode_queue(bh, inode);
                              need_balance_dirty = 1;
                      }
              }

fs/ext2/fsync.c Tue Nov 21 16:01:15 2000 renamed from fs/ext2/fsync.c.~1~ Tue Nov 21 15:47:48 2000 +13 -119

@@ -28,98 +28,6 @@
 #include <linux/smp_lock.h>
 
 
-#define blocksize    (EXT2_BLOCK_SIZE(inode->i_sb))
-#define addr_per_block       (EXT2_ADDR_PER_BLOCK(inode->i_sb))
-
-static int sync_indirect(struct inode * inode, u32 * block, int wait)
-{
-     struct buffer_head * bh;
-
-     if (!*block)
-             return 0;
-     bh = get_hash_table(inode->i_dev, le32_to_cpu(*block), blocksize);
-     if (!bh)
-             return 0;
-     if (wait && buffer_req(bh) && !buffer_uptodate(bh)) {
-             /* There can be a parallell read(2) that started read-I/O
-                on the buffer so we can't assume that there's been
-                an I/O error without first waiting I/O completation. */
-             wait_on_buffer(bh);
-             if (!buffer_uptodate(bh))
-             {
-                     brelse (bh);
-                     return -1;
-             }
-     }
-     if (wait || !buffer_uptodate(bh) || !buffer_dirty(bh)) {
-             if (wait)
-                     /* when we return from fsync all the blocks
-                        must be _just_ stored on disk */
-                     wait_on_buffer(bh);
-             brelse(bh);
-             return 0;
-     }
-     ll_rw_block(WRITE, 1, &bh);
-     atomic_dec(&bh->b_count);
-     return 0;
-}
-
-static int sync_iblock(struct inode * inode, u32 * iblock,
-                     struct buffer_head ** bh, int wait)
-{
-     int rc, tmp;
-
-     *bh = NULL;
-     tmp = le32_to_cpu(*iblock);
-     if (!tmp)
-             return 0;
-     rc = sync_indirect(inode, iblock, wait);
-     if (rc)
-             return rc;
-     *bh = bread(inode->i_dev, tmp, blocksize);
-     if (!*bh)
-             return -1;
-     return 0;
-}
-
-static int sync_dindirect(struct inode * inode, u32 * diblock, int wait)
-{
-     int i;
-     struct buffer_head * dind_bh;
-     int rc, err = 0;
-
-     rc = sync_iblock(inode, diblock, &dind_bh, wait);
-     if (rc || !dind_bh)
-             return rc;
-
-     for (i = 0; i < addr_per_block; i++) {
-             rc = sync_indirect(inode, ((u32 *) dind_bh->b_data) + i, wait);
-             if (rc)
-                     err = rc;
-     }
-     brelse(dind_bh);
-     return err;
-}
-
-static int sync_tindirect(struct inode * inode, u32 * tiblock, int wait)
-{
-     int i;
-     struct buffer_head * tind_bh;
-     int rc, err = 0;
-
-     rc = sync_iblock(inode, tiblock, &tind_bh, wait);
-     if (rc || !tind_bh)
-             return rc;
-
-     for (i = 0; i < addr_per_block; i++) {
-             rc = sync_dindirect(inode, ((u32 *) tind_bh->b_data) + i, wait);
-             if (rc)
-                     err = rc;
-     }
-     brelse(tind_bh);
-     return err;
-}
-
 /*
  *   File may be NULL when we are called. Perhaps we shouldn't
  *   even pass file to fsync ?

@@ -127,34 +35,20 @@
 
 int ext2_sync_file(struct file * file, struct dentry *dentry, int datasync)
 {
-     int wait, err = 0;
      struct inode *inode = dentry->d_inode;
+     return ext2_fsync_inode(inode, datasync);
+}
 
-     lock_kernel();
-     if (S_ISLNK(inode->i_mode) && !(inode->i_blocks))
-             /*
-              * Don't sync fast links!
-              */
-             goto skip;
-
-     err = generic_buffer_fdatasync(inode, 0, ~0UL);
-
-     for (wait=0; wait<=1; wait++)
-     {
-             err |= sync_indirect(inode,
-                                  inode->u.ext2_i.i_data+EXT2_IND_BLOCK,
-                                  wait);
-             err |= sync_dindirect(inode,
-                                   inode->u.ext2_i.i_data+EXT2_DIND_BLOCK,
-                                   wait);
-             err |= sync_tindirect(inode,
-                                   inode->u.ext2_i.i_data+EXT2_TIND_BLOCK,
-                                   wait);
-     }
-skip:
-     if ((inode->i_state & I_DIRTY_DATASYNC) ||
-         ((inode->i_state & I_DIRTY) && !datasync))
-             err |= ext2_sync_inode (inode);
-     unlock_kernel();
+int ext2_fsync_inode(struct inode *inode, int datasync)
+{
+     int err;
+
+     err  = fsync_inode_buffers(inode);
+     if (!(inode->i_state & I_DIRTY))
+             return err;
+     if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
+             return err;
+
+     err |= ext2_sync_inode(inode);
      return err ? -EIO : 0;
 }

fs/ext2/inode.c Tue Nov 21 16:01:15 2000 renamed from fs/ext2/inode.c.~1~ Tue Nov 21 15:40:22 2000 +6 -6

@@ -404,7 +404,7 @@
              branch[n].p = (u32*) bh->b_data + offsets[n];
              *branch[n].p = branch[n].key;
              mark_buffer_uptodate(bh, 1);
-             mark_buffer_dirty(bh);
+             mark_buffer_dirty_inode(bh, inode);
              if (IS_SYNC(inode) || inode->u.ext2_i.i_osync) {
                      ll_rw_block (WRITE, 1, &bh);
                      wait_on_buffer (bh);

@@ -469,7 +469,7 @@
 
      /* had we spliced it onto indirect block? */
      if (where->bh) {
-             mark_buffer_dirty(where->bh);
+             mark_buffer_dirty_inode(where->bh, inode);
              if (IS_SYNC(inode) || inode->u.ext2_i.i_osync) {
                      ll_rw_block (WRITE, 1, &where->bh);
                      wait_on_buffer(where->bh);

@@ -591,7 +591,7 @@
                              wait_on_buffer(bh);
                      memset(bh->b_data, 0, inode->i_sb->s_blocksize);
                      mark_buffer_uptodate(bh, 1);
-                     mark_buffer_dirty(bh);
+                     mark_buffer_dirty_inode(bh, inode);
              }
              return bh;
      }

@@ -907,7 +907,7 @@
              if (partial == chain)
                      mark_inode_dirty(inode);
              else
-                     mark_buffer_dirty(partial->bh);
+                     mark_buffer_dirty_inode(partial->bh, inode);
              ext2_free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
      }
      /* Clear the ends of indirect blocks on the shared branch */

@@ -916,7 +916,7 @@
                                 partial->p + 1,
                                 (u32*)partial->bh->b_data + addr_per_block,
                                 (chain+n-1) - partial);
-             mark_buffer_dirty(partial->bh);
+             mark_buffer_dirty_inode(partial->bh, inode);
              if (IS_SYNC(inode)) {
                      ll_rw_block (WRITE, 1, &partial->bh);
                      wait_on_buffer (partial->bh);

@@ -1208,7 +1208,7 @@
              raw_inode->i_block[0] = cpu_to_le32(kdev_t_to_nr(inode->i_rdev));
      else for (block = 0; block < EXT2_N_BLOCKS; block++)
              raw_inode->i_block[block] = inode->u.ext2_i.i_data[block];
-     mark_buffer_dirty(bh);
+     mark_buffer_dirty_inode(bh, inode);
      if (do_sync) {
              ll_rw_block (WRITE, 1, &bh);
              wait_on_buffer (bh);

fs/ext2/namei.c Tue Nov 21 16:01:15 2000 renamed from fs/ext2/namei.c.~1~ Tue Nov 21 15:40:22 2000 +5 -5

@@ -296,7 +296,7 @@
                      dir->u.ext2_i.i_flags &= ~EXT2_BTREE_FL;
                      mark_inode_dirty(dir);
                      dir->i_version = ++event;
-                     mark_buffer_dirty(bh);
+                     mark_buffer_dirty_inode(bh, dir);
                      if (IS_SYNC(dir)) {
                              ll_rw_block (WRITE, 1, &bh);
                              wait_on_buffer (bh);

@@ -337,7 +337,7 @@
                      else
                              de->inode = 0;
                      dir->i_version = ++event;
-                     mark_buffer_dirty(bh);
+                     mark_buffer_dirty_inode(bh, dir);
                      if (IS_SYNC(dir)) {
                              ll_rw_block (WRITE, 1, &bh);
                              wait_on_buffer (bh);

@@ -449,7 +449,7 @@
      strcpy (de->name, "..");
      ext2_set_de_type(dir->i_sb, de, S_IFDIR);
      inode->i_nlink = 2;
-     mark_buffer_dirty(dir_block);
+     mark_buffer_dirty_inode(dir_block, dir);
      brelse (dir_block);
      inode->i_mode = S_IFDIR | mode;
      if (dir->i_mode & S_ISGID)

@@ -755,7 +755,7 @@
                                            EXT2_FEATURE_INCOMPAT_FILETYPE))
                      new_de->file_type = old_de->file_type;
              new_dir->i_version = ++event;
-             mark_buffer_dirty(new_bh);
+             mark_buffer_dirty_inode(new_bh, new_dir);
              if (IS_SYNC(new_dir)) {
                      ll_rw_block (WRITE, 1, &new_bh);
                      wait_on_buffer (new_bh);

@@ -786,7 +786,7 @@
      mark_inode_dirty(old_dir);
      if (dir_bh) {
              PARENT_INO(dir_bh->b_data) = le32_to_cpu(new_dir->i_ino);
-             mark_buffer_dirty(dir_bh);
+             mark_buffer_dirty_inode(dir_bh, old_inode);
              old_dir->i_nlink--;
              mark_inode_dirty(old_dir);
              if (new_inode) {

include/linux/ext2_fs.h Tue Nov 21 16:01:15 2000 renamed from include/linux/ext2_fs.h.~1~ Tue Nov 21 15:40:22 2000 +1 -0

@@ -549,6 +549,7 @@
 
 /* fsync.c */
 extern int ext2_sync_file (struct file *, struct dentry *, int);
+extern int ext2_fsync_inode (struct inode *, int);
 
 /* ialloc.c */
 extern struct inode * ext2_new_inode (const struct inode *, int, int *);

mm/filemap.c Tue Nov 21 16:01:15 2000 renamed from mm/filemap.c.~1~ Tue Nov 21 15:47:48 2000 +6 -0

@@ -2521,8 +2521,14 @@
      if (cached_page)
              page_cache_free(cached_page);
 
+     /* For now, when the user asks for O_SYNC, we'll actually
+      * provide O_DSYNC. */
+     if ((status >= 0) && (file->f_flags & O_SYNC))
+             status = generic_osync_inode(inode, 1); /* 1 means datasync */
+
      err = written ? written : status;
 out:
+
      up(&inode->i_sem);
      return err;
 fail_write:

Quoted 4 lines

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

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

I have not implemented O_SYNC in NWFS, but it looks like I need to add it before posting the final patches. This patch appears to force write-through of only dirty inodes, and allow reads to continue from cache. Is this assumption correct

Hi,

Quoted 1 line · Jeff V. Merkey

Quoted 4 lines

I have not implemented O_SYNC in NWFS, but it looks like I need to add it before posting the final patches. This patch appears to force write-through of only dirty inodes, and allow reads to continue from cache. Is this assumption correct

Yes: O_SYNC is not required to force reads to be made from disk. SingleUnix has an "O_RSYNC" option which does that, but O_SYNC and O_DSYNC don't imply that.

Cheers,
Stephen

Quoted 9 lines · Stephen C. Tweedie

Hi,

Quoted 5 lines · Jeff V. Merkey

I have not implemented O_SYNC in NWFS, but it looks like I need to add it before posting the final patches. This patch appears to force write-through of only dirty inodes, and allow reads to continue from cache. Is this assumption correct

Quoted 3 lines

Yes: O_SYNC is not required to force reads to be made from disk. SingleUnix has an "O_RSYNC" option which does that, but O_SYNC and O_DSYNC don't imply that.

Cool. ORACLE is going to **SMOKE** on EXT2 with this change.

Cool. ORACLE is going to **SMOKE** on EXT2 with this change.