On Tue, 2024-02-06 at 12:05 +0000, Maximilian Heyne wrote: > 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)) Tip: Use fallocate for faster allocations. > 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. > > Signed-off-by: Maximilian Heyne <mheyne@xxxxxxxxx> > --- > fs/ext4/resize.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c > index 4d4a5a32e310..3433e83bb7a3 100644 > --- a/fs/ext4/resize.c > +++ b/fs/ext4/resize.c > @@ -1602,7 +1602,9 @@ static int ext4_flex_group_add(struct super_block *sb, > 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); > + unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb); > + int meta_bg = ext4_has_feature_meta_bg(sb) && > + metagroup >= le32_to_cpu(es->s_first_meta_bg); Instead of creating a new variable, please use existing variable `gdb_num`. > sector_t padding_blocks = meta_bg ? 0 : sbi->s_sbh->b_blocknr - > ext4_group_first_block_no(sb, 0); > -- > 2.40.1 Have tested it on different filesystem setups, it does stop corruption. > > > > > Amazon Development Center Germany GmbH > Krausenstr. 38 > 10117 Berlin > Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss > Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B > Sitz: Berlin > Ust-ID: DE 289 237 879
