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btrfs: simplify adding pages in btrfs_add_compressed_bio_pages 

btrfs_add_compressed_bio_pages is needlessly complicated.  Instead
of iterating over the logic disk offset just to add pages to the bio
use a simple offset starting at 0, which also removes most of the
claiming.  Additionally __bio_add_pages already takes care of the
assert that the bio is always properly sized, and btrfs_submit_bio
called right after asserts that the bio size is non-zero.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Christoph Hellwig 2023-03-14 17:51:10 +01:00 committed by David Sterba
parent 4513cb0c40
commit 43fa4219bc
1 changed files with 7 additions and 27 deletions
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34
fs/btrfs/compression.c
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@ -258,37 +258,17 @@ static void end_compressed_bio_write(struct btrfs_bio *bbio)
static void btrfs_add_compressed_bio_pages(struct compressed_bio *cb)
{
struct btrfs_fs_info *fs_info = cb->bbio.inode->root->fs_info;
struct bio *bio = &cb->bbio.bio;
u64 disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT;
u64 cur_disk_byte = disk_bytenr;
u32 offset = 0;
while (cur_disk_byte < disk_bytenr + cb->compressed_len) {
u64 offset = cur_disk_byte - disk_bytenr;
unsigned int index = offset >> PAGE_SHIFT;
unsigned int real_size;
unsigned int added;
struct page *page = cb->compressed_pages[index];
while (offset < cb->compressed_len) {
u32 len = min_t(u32, cb->compressed_len - offset, PAGE_SIZE);
/*
* We have various limit on the real read size:
* - page boundary
* - compressed length boundary
*/
real_size = min_t(u64, U32_MAX, PAGE_SIZE - offset_in_page(offset));
real_size = min_t(u64, real_size, cb->compressed_len - offset);
ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
added = bio_add_page(bio, page, real_size, offset_in_page(offset));
/*
* Maximum compressed extent is smaller than bio size limit,
* thus bio_add_page() should always success.
*/
ASSERT(added == real_size);
cur_disk_byte += added;
/* Maximum compressed extent is smaller than bio size limit. */
__bio_add_page(bio, cb->compressed_pages[offset >> PAGE_SHIFT],
len, 0);
offset += len;
}
ASSERT(bio->bi_iter.bi_size);
}
/*