On Sun, Nov 20, 2022 at 01:47:17PM +0100, Christoph Hellwig wrote: > Currently btrfs handles checksum validation and repair in the end I/O > handler for the btrfs_bio. This leads to a lot of duplicate code > plus issues with variying semantics or bugs, e.g. > > - the until recently broken repair for compressed extents > - the fact that encoded reads validate the checksums but do not kick > of read repair > - the inconsistent checking of the BTRFS_FS_STATE_NO_CSUMS flag > > This commit revamps the checksum validation and repair code to instead > work below the btrfs_submit_bio interfaces. For this to work we need > to make sure an inode is available, so that is added as a parameter > to btrfs_bio_alloc. With that btrfs_submit_bio can preload > btrfs_bio.csum from the csum tree without help from the upper layers, > and the low-level I/O completion can iterate over the bio and verify > the checksums. > > In case of a checksum failure (or a plain old I/O error), the repair > is now kicked off before the upper level ->end_io handler is invoked. > Tracking of the repair status is massively simplified by just keeping > a small failed_bio structure per bio with failed sectors and otherwise > using the information in the repair bio. The per-inode I/O failure > tree can be entirely removed. > > The saved bvec_iter in the btrfs_bio is now competely managed by > btrfs_submit_bio and must not be accessed by the callers. > > There is one significant behavior change here: If repair fails or > is impossible to start with, the whole bio will be failed to the > upper layer. This is the behavior that all I/O submitters execept > for buffered I/O already emulated in their end_io handler. For > buffered I/O this now means that a large readahead request can > fail due to a single bad sector, but as readahead errors are igored > the following readpage if the sector is actually accessed will > still be able to read. This also matches the I/O failure handling > in other file systems. This patch is apparently doing several things at once, please split it. Thanks.
