linux-ext4 - [PATCH -v2] ext4: make fsync to sync parent dir in no-journal for real this time

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Message-ID: <20150403151614.GD9988@thunk.org>
Date:	Fri, 3 Apr 2015 11:16:14 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org, Frank Mayhar <fmayhar@...gle.com>
Subject: [PATCH -v2] ext4: make fsync to sync parent dir in no-journal for
 real this time

It turns out this patch was buggy; make_indexed_dir() releases the
buffer head, so it was missing a "bh = NULL" in a critical place.
(Note: please try running at least "kvm-xfstests smoke" before
submitting a patch; it only takes about 30 minutes, and in this case
generic/006 would have failed very quickly.)

						- Ted

>From e12fb97222fc41e8442896934f76d39ef99b590a Mon Sep 17 00:00:00 2001
From: Lukas Czerner <lczerner@...hat.com>
Date: Fri, 3 Apr 2015 10:46:58 -0400
Subject: [PATCH] ext4: make fsync to sync parent dir in no-journal for real
 this time

Previously commit 14ece1028b3ed53ffec1b1213ffc6acaf79ad77c added a
support for for syncing parent directory of newly created inodes to
make sure that the inode is not lost after a power failure in
no-journal mode.

However this does not work in majority of cases, namely:
 - if the directory has inline data
 - if the directory is already indexed
 - if the directory already has at least one block and:
	- the new entry fits into it
	- or we've successfully converted it to indexed

So in those cases we might lose the inode entirely even after fsync in
the no-journal mode. This also includes ext2 default mode obviously.

I've noticed this while running xfstest generic/321 and even though the
test should fail (we need to run fsck after a crash in no-journal mode)
I could not find a newly created entries even when if it was fsynced
before.

Fix this by adjusting the ext4_add_entry() successful exit paths to set
the inode EXT4_STATE_NEWENTRY so that fsync has the chance to fsync the
parent directory as well.

Signed-off-by: Lukas Czerner <lczerner@...hat.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Reviewed-by: Jan Kara <jack@...e.cz>
Cc: Frank Mayhar <fmayhar@...gle.com>
Cc: stable@...r.kernel.org
---
 fs/ext4/namei.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index efb64ae..23a0b9b 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1864,7 +1864,7 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
 			  struct inode *inode)
 {
 	struct inode *dir = dentry->d_parent->d_inode;
-	struct buffer_head *bh;
+	struct buffer_head *bh = NULL;
 	struct ext4_dir_entry_2 *de;
 	struct ext4_dir_entry_tail *t;
 	struct super_block *sb;
@@ -1888,14 +1888,14 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
 			return retval;
 		if (retval == 1) {
 			retval = 0;
-			return retval;
+			goto out;
 		}
 	}
 
 	if (is_dx(dir)) {
 		retval = ext4_dx_add_entry(handle, dentry, inode);
 		if (!retval || (retval != ERR_BAD_DX_DIR))
-			return retval;
+			goto out;
 		ext4_clear_inode_flag(dir, EXT4_INODE_INDEX);
 		dx_fallback++;
 		ext4_mark_inode_dirty(handle, dir);
@@ -1907,14 +1907,15 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
 			return PTR_ERR(bh);
 
 		retval = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
-		if (retval != -ENOSPC) {
-			brelse(bh);
-			return retval;
-		}
+		if (retval != -ENOSPC)
+			goto out;
 
 		if (blocks == 1 && !dx_fallback &&
-		    EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_DIR_INDEX))
-			return make_indexed_dir(handle, dentry, inode, bh);
+		    EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_DIR_INDEX)) {
+			retval = make_indexed_dir(handle, dentry, inode, bh);
+			bh = NULL; /* make_indexed_dir releases bh */
+			goto out;
+		}
 		brelse(bh);
 	}
 	bh = ext4_append(handle, dir, &block);
@@ -1930,6 +1931,7 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
 	}
 
 	retval = add_dirent_to_buf(handle, dentry, inode, de, bh);
+out:
 	brelse(bh);
 	if (retval == 0)
 		ext4_set_inode_state(inode, EXT4_STATE_NEWENTRY);
-- 
2.3.0

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