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authorMaximilian Heyne <mheyne@amazon.de>2024-02-15 18:50:09 +0300
committerTheodore Ts'o <tytso@mit.edu>2024-03-07 21:32:54 +0300
commita6b3bfe176e8a5b05ec4447404e412c2a3fc92cc (patch)
tree369347d2a74247316c746064dc0ff7b419b29c20 /fs/ext4/resize.c
parentfa60629380bbbf0952d2eb906da187b171f54529 (diff)
downloadlinux-a6b3bfe176e8a5b05ec4447404e412c2a3fc92cc.tar.xz
ext4: fix corruption during on-line resize
We observed a corruption during on-line resize of a file system that is larger than 16 TiB with 4k block size. With having more then 2^32 blocks resize_inode is turned off by default by mke2fs. The issue can be reproduced on a smaller file system for convenience by explicitly turning off resize_inode. An on-line resize across an 8 GiB boundary (the size of a meta block group in this setup) then leads to a corruption: dev=/dev/<some_dev> # should be >= 16 GiB mkdir -p /corruption /sbin/mke2fs -t ext4 -b 4096 -O ^resize_inode $dev $((2 * 2**21 - 2**15)) mount -t ext4 $dev /corruption dd if=/dev/zero bs=4096 of=/corruption/test count=$((2*2**21 - 4*2**15)) sha1sum /corruption/test # 79d2658b39dcfd77274e435b0934028adafaab11 /corruption/test /sbin/resize2fs $dev $((2*2**21)) # drop page cache to force reload the block from disk echo 1 > /proc/sys/vm/drop_caches sha1sum /corruption/test # 3c2abc63cbf1a94c9e6977e0fbd72cd832c4d5c3 /corruption/test 2^21 = 2^15*2^6 equals 8 GiB whereof 2^15 is the number of blocks per block group and 2^6 are the number of block groups that make a meta block group. The last checksum might be different depending on how the file is laid out across the physical blocks. The actual corruption occurs at physical block 63*2^15 = 2064384 which would be the location of the backup of the meta block group's block descriptor. During the on-line resize the file system will be converted to meta_bg starting at s_first_meta_bg which is 2 in the example - meaning all block groups after 16 GiB. However, in ext4_flex_group_add we might add block groups that are not part of the first meta block group yet. In the reproducer we achieved this by substracting the size of a whole block group from the point where the meta block group would start. This must be considered when updating the backup block group descriptors to follow the non-meta_bg layout. The fix is to add a test whether the group to add is already part of the meta block group or not. Fixes: 01f795f9e0d67 ("ext4: add online resizing support for meta_bg and 64-bit file systems") Cc: <stable@vger.kernel.org> Signed-off-by: Maximilian Heyne <mheyne@amazon.de> Tested-by: Srivathsa Dara <srivathsa.d.dara@oracle.com> Reviewed-by: Srivathsa Dara <srivathsa.d.dara@oracle.com> Link: https://lore.kernel.org/r/20240215155009.94493-1-mheyne@amazon.de Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/resize.c')
-rw-r--r--fs/ext4/resize.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 4d4a5a32e310..3c0d12382e06 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1602,7 +1602,8 @@ exit_journal:
int gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
int gdb_num_end = ((group + flex_gd->count - 1) /
EXT4_DESC_PER_BLOCK(sb));
- int meta_bg = ext4_has_feature_meta_bg(sb);
+ int meta_bg = ext4_has_feature_meta_bg(sb) &&
+ gdb_num >= le32_to_cpu(es->s_first_meta_bg);
sector_t padding_blocks = meta_bg ? 0 : sbi->s_sbh->b_blocknr -
ext4_group_first_block_no(sb, 0);