[PATCH 53/91] ext4: fix BUG_ON() in ext4_ext_insert_extent()

From: Willy Tarreau
Date: Sun Feb 05 2012 - 17:35:01 EST

2.6.27-longterm review patch. If anyone has any objections, please let us know.


Does not corrispond with a direct commit in Linus's tree as it was fixed
differently in the 3.0 release.

We will meet with a BUG_ON() if following script is run.

mkfs.ext4 -b 4096 /dev/sdb1 1000000
mount -t ext4 /dev/sdb1 /mnt/sdb1
fallocate -l 100M /mnt/sdb1/test
dd if=/dev/zero of=/mnt/sdb1/test conv=notrunc bs=256k count=1
seek=`expr $i \* 2`
umount /mnt/sdb1
mount -t ext4 /dev/sdb1 /mnt/sdb1
dd if=/dev/zero of=/mnt/sdb1/test conv=notrunc bs=256k count=1 seek=341
umount /mnt/sdb1
mount /dev/sdb1 /mnt/sdb1
dd if=/dev/zero of=/mnt/sdb1/test conv=notrunc bs=256k count=1 seek=340

The reason is that it forgot to mark dirty when splitting two extents in
ext4_ext_convert_to_initialized(). Althrough ex has been updated in
memory, it is not dirtied both in ext4_ext_convert_to_initialized() and
ext4_ext_insert_extent(). The disk layout is corrupted. Then it will
meet with a BUG_ON() when writting at the start of that extent again.

Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Xiaoyun Mao <xiaoyun.maoxy@xxxxxxxxxxxxxx>
Cc: Yingbin Wang <yingbin.wangyb@xxxxxxxxxxxxxx>
Cc: Jia Wan <jia.wanj@xxxxxxxxxxxxxx>
Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
fs/ext4/extents.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

Index: longterm-2.6.27/fs/ext4/extents.c
--- longterm-2.6.27.orig/fs/ext4/extents.c 2012-02-05 22:34:33.413914999 +0100
+++ longterm-2.6.27/fs/ext4/extents.c 2012-02-05 22:34:42.416916530 +0100
@@ -2327,6 +2327,7 @@
ex1 = ex;
ex1->ee_len = cpu_to_le16(iblock - ee_block);
+ ext4_ext_dirty(handle, inode, path + depth);
ex2 = &newex;

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