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Btrfs: change how we iterate bios in endio
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Since dio submit has used bio_clone_fast, the submitted bio may not have a
reliable bi_vcnt, for the bio vector iterations in checksum related
functions, bio->bi_iter is not modified yet and it's safe to use
bio_for_each_segment, while for those bio vector iterations in dio read's
endio, we now save a copy of bvec_iter in struct btrfs_io_bio when cloning
bios and use the helper __bio_for_each_segment with the saved bvec_iter to
access each bvec.

Also for dio reads which don't get split, we also need to save a copy of
bio iterator in btrfs_bio_clone to let __bio_for_each_segments to access
each bvec in dio read's endio.  Note that it doesn't affect other calls of
btrfs_bio_clone() because they don't need to use this iterator.

Signed-off-by: Liu Bo <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>
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@kdave
Liu Bo authored and kdave committed Jun 19, 2017
1 parent 725130b commit 17347ce
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Showing 4 changed files with 37 additions and 32 deletions.
2 changes: 2 additions & 0 deletions fs/btrfs/extent_io.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2700,6 +2700,7 @@ struct bio *btrfs_bio_clone(struct bio *bio, gfp_t gfp_mask)
btrfs_bio->csum = NULL;
btrfs_bio->csum_allocated = NULL;
btrfs_bio->end_io = NULL;
btrfs_bio->iter = bio->bi_iter;
}
return new;
}
Expand Down Expand Up @@ -2736,6 +2737,7 @@ struct bio *btrfs_bio_clone_partial(struct bio *orig, gfp_t gfp_mask,
btrfs_bio->end_io = NULL;

bio_trim(bio, offset >> 9, size >> 9);
btrfs_bio->iter = bio->bi_iter;
return bio;
}

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31 changes: 15 additions & 16 deletions fs/btrfs/file-item.c
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Original file line number Diff line number Diff line change
Expand Up @@ -164,7 +164,8 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
u64 logical_offset, u32 *dst, int dio)
{
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct bio_vec *bvec;
struct bio_vec bvec;
struct bvec_iter iter;
struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
struct btrfs_csum_item *item = NULL;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
Expand All @@ -177,7 +178,7 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
u64 page_bytes_left;
u32 diff;
int nblocks;
int count = 0, i;
int count = 0;
u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);

path = btrfs_alloc_path();
Expand Down Expand Up @@ -206,8 +207,6 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
if (bio->bi_iter.bi_size > PAGE_SIZE * 8)
path->reada = READA_FORWARD;

WARN_ON(bio->bi_vcnt <= 0);

/*
* the free space stuff is only read when it hasn't been
* updated in the current transaction. So, we can safely
Expand All @@ -223,13 +222,13 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
if (dio)
offset = logical_offset;

bio_for_each_segment_all(bvec, bio, i) {
page_bytes_left = bvec->bv_len;
bio_for_each_segment(bvec, bio, iter) {
page_bytes_left = bvec.bv_len;
if (count)
goto next;

if (!dio)
offset = page_offset(bvec->bv_page) + bvec->bv_offset;
offset = page_offset(bvec.bv_page) + bvec.bv_offset;
count = btrfs_find_ordered_sum(inode, offset, disk_bytenr,
(u32 *)csum, nblocks);
if (count)
Expand Down Expand Up @@ -440,15 +439,15 @@ int btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
struct btrfs_ordered_sum *sums;
struct btrfs_ordered_extent *ordered = NULL;
char *data;
struct bio_vec *bvec;
struct bvec_iter iter;
struct bio_vec bvec;
int index;
int nr_sectors;
int i, j;
unsigned long total_bytes = 0;
unsigned long this_sum_bytes = 0;
int i;
u64 offset;

WARN_ON(bio->bi_vcnt <= 0);
sums = kzalloc(btrfs_ordered_sum_size(fs_info, bio->bi_iter.bi_size),
GFP_NOFS);
if (!sums)
Expand All @@ -465,19 +464,19 @@ int btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
sums->bytenr = (u64)bio->bi_iter.bi_sector << 9;
index = 0;

bio_for_each_segment_all(bvec, bio, j) {
bio_for_each_segment(bvec, bio, iter) {
if (!contig)
offset = page_offset(bvec->bv_page) + bvec->bv_offset;
offset = page_offset(bvec.bv_page) + bvec.bv_offset;

if (!ordered) {
ordered = btrfs_lookup_ordered_extent(inode, offset);
BUG_ON(!ordered); /* Logic error */
}

data = kmap_atomic(bvec->bv_page);
data = kmap_atomic(bvec.bv_page);

nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info,
bvec->bv_len + fs_info->sectorsize
bvec.bv_len + fs_info->sectorsize
- 1);

for (i = 0; i < nr_sectors; i++) {
Expand All @@ -504,12 +503,12 @@ int btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
+ total_bytes;
index = 0;

data = kmap_atomic(bvec->bv_page);
data = kmap_atomic(bvec.bv_page);
}

sums->sums[index] = ~(u32)0;
sums->sums[index]
= btrfs_csum_data(data + bvec->bv_offset
= btrfs_csum_data(data + bvec.bv_offset
+ (i * fs_info->sectorsize),
sums->sums[index],
fs_info->sectorsize);
Expand Down
35 changes: 19 additions & 16 deletions fs/btrfs/inode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7989,6 +7989,7 @@ static int dio_read_error(struct inode *inode, struct bio *failed_bio,
struct bio *bio;
int isector;
int read_mode = 0;
int segs;
int ret;

BUG_ON(bio_op(failed_bio) == REQ_OP_WRITE);
Expand All @@ -8004,9 +8005,9 @@ static int dio_read_error(struct inode *inode, struct bio *failed_bio,
return -EIO;
}

if ((failed_bio->bi_vcnt > 1)
|| (failed_bio->bi_io_vec->bv_len
> btrfs_inode_sectorsize(inode)))
segs = bio_segments(failed_bio);
if (segs > 1 ||
(failed_bio->bi_io_vec->bv_len > btrfs_inode_sectorsize(inode)))
read_mode |= REQ_FAILFAST_DEV;

isector = start - btrfs_io_bio(failed_bio)->logical;
Expand Down Expand Up @@ -8069,31 +8070,32 @@ static int __btrfs_correct_data_nocsum(struct inode *inode,
struct btrfs_io_bio *io_bio)
{
struct btrfs_fs_info *fs_info;
struct bio_vec *bvec;
struct bio_vec bvec;
struct bvec_iter iter;
struct btrfs_retry_complete done;
u64 start;
unsigned int pgoff;
u32 sectorsize;
int nr_sectors;
int i;
int ret;

fs_info = BTRFS_I(inode)->root->fs_info;
sectorsize = fs_info->sectorsize;

start = io_bio->logical;
done.inode = inode;
io_bio->bio.bi_iter = io_bio->iter;

bio_for_each_segment_all(bvec, &io_bio->bio, i) {
nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec->bv_len);
pgoff = bvec->bv_offset;
bio_for_each_segment(bvec, &io_bio->bio, iter) {
nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec.bv_len);
pgoff = bvec.bv_offset;

next_block_or_try_again:
done.uptodate = 0;
done.start = start;
init_completion(&done.done);

ret = dio_read_error(inode, &io_bio->bio, bvec->bv_page,
ret = dio_read_error(inode, &io_bio->bio, bvec.bv_page,
pgoff, start, start + sectorsize - 1,
io_bio->mirror_num,
btrfs_retry_endio_nocsum, &done);
Expand Down Expand Up @@ -8166,15 +8168,15 @@ static int __btrfs_subio_endio_read(struct inode *inode,
struct btrfs_io_bio *io_bio, int err)
{
struct btrfs_fs_info *fs_info;
struct bio_vec *bvec;
struct bio_vec bvec;
struct bvec_iter iter;
struct btrfs_retry_complete done;
u64 start;
u64 offset = 0;
u32 sectorsize;
int nr_sectors;
unsigned int pgoff;
int csum_pos;
int i;
int ret;

fs_info = BTRFS_I(inode)->root->fs_info;
Expand All @@ -8183,15 +8185,16 @@ static int __btrfs_subio_endio_read(struct inode *inode,
err = 0;
start = io_bio->logical;
done.inode = inode;
io_bio->bio.bi_iter = io_bio->iter;

bio_for_each_segment_all(bvec, &io_bio->bio, i) {
nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec->bv_len);
bio_for_each_segment(bvec, &io_bio->bio, iter) {
nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec.bv_len);

pgoff = bvec->bv_offset;
pgoff = bvec.bv_offset;
next_block:
csum_pos = BTRFS_BYTES_TO_BLKS(fs_info, offset);
ret = __readpage_endio_check(inode, io_bio, csum_pos,
bvec->bv_page, pgoff, start,
bvec.bv_page, pgoff, start,
sectorsize);
if (likely(!ret))
goto next;
Expand All @@ -8200,7 +8203,7 @@ static int __btrfs_subio_endio_read(struct inode *inode,
done.start = start;
init_completion(&done.done);

ret = dio_read_error(inode, &io_bio->bio, bvec->bv_page,
ret = dio_read_error(inode, &io_bio->bio, bvec.bv_page,
pgoff, start, start + sectorsize - 1,
io_bio->mirror_num,
btrfs_retry_endio, &done);
Expand Down
1 change: 1 addition & 0 deletions fs/btrfs/volumes.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,7 @@ struct btrfs_io_bio {
u8 csum_inline[BTRFS_BIO_INLINE_CSUM_SIZE];
u8 *csum_allocated;
btrfs_io_bio_end_io_t *end_io;
struct bvec_iter iter;
struct bio bio;
};

Expand Down

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