e3c62324e4
[BUG] When relocating partial preallocated data extents (part of the preallocated extent is written) for subpage, it can cause the following false alert and make the relocation to fail: BTRFS info (device dm-3): balance: start -d BTRFS info (device dm-3): relocating block group 13631488 flags data BTRFS warning (device dm-3): csum failed root -9 ino 257 off 4096 csum 0x98757625 expected csum 0x00000000 mirror 1 BTRFS error (device dm-3): bdev /dev/mapper/arm_nvme-test errs: wr 0, rd 0, flush 0, corrupt 1, gen 0 BTRFS warning (device dm-3): csum failed root -9 ino 257 off 4096 csum 0x98757625 expected csum 0x00000000 mirror 1 BTRFS error (device dm-3): bdev /dev/mapper/arm_nvme-test errs: wr 0, rd 0, flush 0, corrupt 2, gen 0 BTRFS info (device dm-3): balance: ended with status: -5 The minimal script to reproduce looks like this: mkfs.btrfs -f -s 4k $dev mount $dev -o nospace_cache $mnt xfs_io -f -c "falloc 0 8k" $mnt/file xfs_io -f -c "pwrite 0 4k" $mnt/file btrfs balance start -d $mnt [CAUSE] Function btrfs_verify_data_csum() checks if the full range has EXTENT_NODATASUM bit for data reloc inode, if *all* bytes of the range have EXTENT_NODATASUM bit, then it skip the range. This works pretty well for regular sectorsize, as in that case btrfs_verify_data_csum() is called for each sector, thus no problem at all. But for subpage case, btrfs_verify_data_csum() is called on each bvec, which can contain several sectors, and since it checks *all* bytes for EXTENT_NODATASUM bit, if we have some range with csum, then we will continue checking all the sectors. For the preallocated sectors, it doesn't have any csum, thus obviously the csum won't match and cause the false alert. [FIX] Move the EXTENT_NODATASUM check into the main loop, so that we can check each sector for EXTENT_NODATASUM bit for subpage case. Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.