[PATCH 02/17] btrfs: save bio::bi_iter into btrfs_bio::iter before submitting
From: Qu Wenruo <hidden>
Date: 2021-12-01 05:18:20
Also in:
dm-devel, linux-block
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
Since block layer will advance bio::bi_iter, at endio time we can no longer rely on bio::bi_iter for split bio. But for the incoming btrfs_bio split at btrfs_map_bio() time, we have to ensure endio function is only executed for the split range, not the whole original bio. Thus this patch will introduce a new helper, btrfs_bio_save_iter(), to save bi_iter into btrfs_bio::iter. The following call sites need this helper call: - btrfs_submit_compressed_read() For compressed read. For compressed write it doesn't really care as they use ordered extent. - raid56_parity_write() - raid56_parity_recovery() For RAID56. - submit_stripe_bio() For all other cases. Signed-off-by: Qu Wenruo <redacted> --- fs/btrfs/compression.c | 3 +++ fs/btrfs/raid56.c | 2 ++ fs/btrfs/volumes.c | 14 ++++++++++++++ fs/btrfs/volumes.h | 18 ++++++++++++++++++ 4 files changed, 37 insertions(+)
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index e776956d5bc9..cc8d13369f53 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c@@ -870,6 +870,9 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, /* include any pages we added in add_ra-bio_pages */ cb->len = bio->bi_iter.bi_size; + /* Save bi_iter so that end_bio_extent_readpage() won't freak out. */ + btrfs_bio_save_iter(btrfs_bio(bio)); + while (cur_disk_byte < disk_bytenr + compressed_len) { u64 offset = cur_disk_byte - disk_bytenr; unsigned int index = offset >> PAGE_SHIFT;
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 0e239a4c3b26..13e726c88a81 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c@@ -1731,6 +1731,7 @@ int raid56_parity_write(struct bio *bio, struct btrfs_io_context *bioc, return PTR_ERR(rbio); } bio_list_add(&rbio->bio_list, bio); + btrfs_bio_save_iter(btrfs_bio(bio)); rbio->bio_list_bytes = bio->bi_iter.bi_size; rbio->operation = BTRFS_RBIO_WRITE;
@@ -2135,6 +2136,7 @@ int raid56_parity_recover(struct bio *bio, struct btrfs_io_context *bioc, rbio->operation = BTRFS_RBIO_READ_REBUILD; bio_list_add(&rbio->bio_list, bio); + btrfs_bio_save_iter(btrfs_bio(bio)); rbio->bio_list_bytes = bio->bi_iter.bi_size; rbio->faila = find_logical_bio_stripe(rbio, bio);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f38c230111be..b70037cc1a51 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c@@ -6829,6 +6829,20 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio, BUG(); } + /* + * At endio time, bi_iter is no longer reliable, thus we have to save + * current bi_iter into btrfs_bio so that even for split bio we can + * iterate only the split part. + * + * And this has to be done before any bioc error, as endio functions + * will rely on bbio::iter. + * + * For bio create by btrfs_bio_slit() or btrfs_bio_clone*(), it's + * already set, but we can still have original bio which has its + * iter not initialized. + */ + btrfs_bio_save_iter(btrfs_bio(bio)); + for (dev_nr = 0; dev_nr < total_devs; dev_nr++) { dev = bioc->stripes[dev_nr].dev; if (!dev || !dev->bdev || test_bit(BTRFS_DEV_STATE_MISSING,
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 3b8130680749..f9178d2c2fd6 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h@@ -334,6 +334,12 @@ struct btrfs_bio { struct btrfs_device *device; u8 *csum; u8 csum_inline[BTRFS_BIO_INLINE_CSUM_SIZE]; + /* + * Saved bio::bi_iter before submission. + * + * This allows us to interate the cloned/split bio properly, as at + * endio time bio::bi_iter is no longer reliable. + */ struct bvec_iter iter; /*
@@ -356,6 +362,18 @@ static inline void btrfs_bio_free_csum(struct btrfs_bio *bbio) } } +/* + * To save bbio::bio->bi_iter into bbio::iter so for callers who need the + * original bi_iter can access the original part of the bio. + * This is especially important for the incoming split btrfs_bio, which needs + * to call its endio for and only for the split range. + */ +static inline void btrfs_bio_save_iter(struct btrfs_bio *bbio) +{ + if (!bbio->iter.bi_size) + bbio->iter = bbio->bio.bi_iter; +} + struct btrfs_io_stripe { struct btrfs_device *dev; u64 physical;
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2.34.1