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bcachefs: Some compression improvements

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In __bio_map_or_bounce(), the check for if the bio is physically
contiguous is improved; it's now more readable and handles multi page
but contiguous bios.

Also when decompressing, we were doing a redundant memcpy in the case
where we were able to use vmap to map a bio contigiously.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2020-05-06 15:37:04 -04:00 committed by Kent Overstreet
parent bc970cecd8
commit c4dd7871ef
1 changed files with 37 additions and 16 deletions
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53
fs/bcachefs/compress.c
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@ -39,6 +39,24 @@ static struct bbuf __bounce_alloc(struct bch_fs *c, unsigned size, int rw)
BUG();
}
static bool bio_phys_contig(struct bio *bio, struct bvec_iter start)
{
struct bio_vec bv;
struct bvec_iter iter;
void *expected_start = NULL;
__bio_for_each_bvec(bv, bio, iter, start) {
if (expected_start &&
expected_start != page_address(bv.bv_page) + bv.bv_offset)
return false;
expected_start = page_address(bv.bv_page) +
bv.bv_offset + bv.bv_len;
}
return true;
}
static struct bbuf __bio_map_or_bounce(struct bch_fs *c, struct bio *bio,
struct bvec_iter start, int rw)
{
@ -48,27 +66,28 @@ static struct bbuf __bio_map_or_bounce(struct bch_fs *c, struct bio *bio,
unsigned nr_pages = 0;
struct page *stack_pages[16];
struct page **pages = NULL;
bool first = true;
unsigned prev_end = PAGE_SIZE;
void *data;
BUG_ON(bvec_iter_sectors(start) > c->sb.encoded_extent_max);
#ifndef CONFIG_HIGHMEM
__bio_for_each_bvec(bv, bio, iter, start) {
if (bv.bv_len == start.bi_size)
return (struct bbuf) {
.b = page_address(bv.bv_page) + bv.bv_offset,
.type = BB_NONE, .rw = rw
};
}
#endif
if (!IS_ENABLED(CONFIG_HIGHMEM) &&
bio_phys_contig(bio, start))
return (struct bbuf) {
.b = page_address(bio_iter_page(bio, start)) +
bio_iter_offset(bio, start),
.type = BB_NONE, .rw = rw
};
/* check if we can map the pages contiguously: */
__bio_for_each_segment(bv, bio, iter, start) {
if ((!first && bv.bv_offset) ||
prev_end != PAGE_SIZE)
if (iter.bi_size != start.bi_size &&
bv.bv_offset)
goto bounce;
if (bv.bv_len < iter.bi_size &&
bv.bv_offset + bv.bv_len < PAGE_SIZE)
goto bounce;
prev_end = bv.bv_offset + bv.bv_len;
nr_pages++;
}
@ -264,7 +283,8 @@ int bch2_bio_uncompress(struct bch_fs *c, struct bio *src,
if (ret)
goto err;
if (dst_data.type != BB_NONE)
if (dst_data.type != BB_NONE &&
dst_data.type != BB_VMAP)
memcpy_to_bio(dst, dst_iter, dst_data.b + (crc.offset << 9));
err:
bio_unmap_or_unbounce(c, dst_data);
@ -407,7 +427,8 @@ static unsigned __bio_compress(struct bch_fs *c,
memset(dst_data.b + *dst_len, 0, pad);
*dst_len += pad;
if (dst_data.type != BB_NONE)
if (dst_data.type != BB_NONE &&
dst_data.type != BB_VMAP)
memcpy_to_bio(dst, dst->bi_iter, dst_data.b);
BUG_ON(!*dst_len || *dst_len > dst->bi_iter.bi_size);