[Devel] [PATCH RH7] ext4: do not zeroout extents beyond i_disksize

[Kirill Tkhai]

From: Jan Kara <jack at suse.cz>

(Eugeniy, please RK this where it is not applied. At least 163.46 needs it).

ms commit 801674f34ecf

We do not want to create initialized extents beyond end of file because
for e2fsck it is impossible to distinguish them from a case of corrupted
file size / extent tree and so it complains like:

Inode 12, i_size is 147456, should be 163840.  Fix? no

Code in ext4_ext_convert_to_initialized() and
ext4_split_convert_extents() try to make sure it does not create
initialized extents beyond inode size however they check against
inode->i_size which is wrong. They should instead check against
EXT4_I(inode)->i_disksize which is the current inode size on disk.
That's what e2fsck is going to see in case of crash before all dirty
data is written. This bug manifests as generic/456 test failure (with
recent enough fstests where fsx got fixed to properly pass
FALLOC_KEEP_SIZE_FL flags to the kernel) when run with dioread_lock
mount option.

CC: stable at vger.kernel.org
Fixes: 21ca087a3891 ("ext4: Do not zero out uninitialized extents beyond i_size")
Reviewed-by: Lukas Czerner <lczerner at redhat.com>
Signed-off-by: Jan Kara <jack at suse.cz>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Link: https://lore.kernel.org/r/20200331105016.8674-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
---
 fs/ext4/extents.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 74a283d3ce36..6d59c9661e38 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3432,8 +3432,8 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 		(unsigned long long)map->m_lblk, map_len);
 
 	sbi = EXT4_SB(inode->i_sb);
-	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
-		inode->i_sb->s_blocksize_bits;
+	eof_block = (EXT4_I(inode)->i_disksize + inode->i_sb->s_blocksize - 1)
+			>> inode->i_sb->s_blocksize_bits;
 	if (eof_block < map->m_lblk + map_len)
 		eof_block = map->m_lblk + map_len;
 
@@ -3686,8 +3686,8 @@ static int ext4_split_convert_extents(handle_t *handle,
 		  __func__, inode->i_ino,
 		  (unsigned long long)map->m_lblk, map->m_len);
 
-	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
-		inode->i_sb->s_blocksize_bits;
+	eof_block = (EXT4_I(inode)->i_disksize + inode->i_sb->s_blocksize - 1)
+			>> inode->i_sb->s_blocksize_bits;
 	if (eof_block < map->m_lblk + map->m_len)
 		eof_block = map->m_lblk + map->m_len;
 	/*