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btrfs: lzo: use folio_iter to handle lzo_decompress_bio()

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Currently lzo_decompress_bio() is using
compressed_bio->compressed_folios[] array to grab each compressed folio.

This is making the code much easier to read, as we only need to maintain
a single iterator, @cur_in, and can easily grab any random folio using
@cur_in >> min_folio_shift as an index.

However lzo_decompress_bio() itself is ensured to only advance to the
next folio at one time, and compressed_folios[] is just a pointer to
each folio of the compressed bio, thus we have no real random access
requirement for lzo_decompress_bio().

Replace the compressed_folios[] access by a helper, get_current_folio(),
which uses folio_iter and an external folio counter to properly switch
the folio when needed.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo
2026-01-20 10:30:08 +10:30
committed by David Sterba
parent 4b7ecd0984
commit 37cc07cab7
1 changed files with 37 additions and 9 deletions
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46
fs/btrfs/lzo.c
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@@ -310,23 +310,43 @@ out:
return ret;
}
static struct folio *get_current_folio(struct compressed_bio *cb, struct folio_iter *fi,
u32 *cur_folio_index, u32 cur_in)
{
struct btrfs_fs_info *fs_info = cb_to_fs_info(cb);
const u32 min_folio_shift = PAGE_SHIFT + fs_info->block_min_order;
ASSERT(cur_folio_index);
/* Need to switch to the next folio. */
if (cur_in >> min_folio_shift != *cur_folio_index) {
/* We can only do the switch one folio a time. */
ASSERT(cur_in >> min_folio_shift == *cur_folio_index + 1);
bio_next_folio(fi, &cb->bbio.bio);
(*cur_folio_index)++;
}
return fi->folio;
}
/*
* Copy the compressed segment payload into @dest.
*
* For the payload there will be no padding, just need to do page switching.
*/
static void copy_compressed_segment(struct compressed_bio *cb,
struct folio_iter *fi, u32 *cur_folio_index,
char *dest, u32 len, u32 *cur_in)
{
struct btrfs_fs_info *fs_info = cb_to_fs_info(cb);
const u32 min_folio_shift = PAGE_SHIFT + fs_info->block_min_order;
u32 orig_in = *cur_in;
while (*cur_in < orig_in + len) {
struct folio *cur_folio = cb->compressed_folios[*cur_in >> min_folio_shift];
u32 copy_len = min_t(u32, orig_in + len - *cur_in,
folio_size(cur_folio) - offset_in_folio(cur_folio, *cur_in));
struct folio *cur_folio = get_current_folio(cb, fi, cur_folio_index, *cur_in);
u32 copy_len;
ASSERT(cur_folio);
copy_len = min_t(u32, orig_in + len - *cur_in,
folio_size(cur_folio) - offset_in_folio(cur_folio, *cur_in));
ASSERT(copy_len);
memcpy_from_folio(dest + *cur_in - orig_in, cur_folio,
@@ -341,7 +361,7 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
struct workspace *workspace = list_entry(ws, struct workspace, list);
const struct btrfs_fs_info *fs_info = cb->bbio.inode->root->fs_info;
const u32 sectorsize = fs_info->sectorsize;
const u32 min_folio_shift = PAGE_SHIFT + fs_info->block_min_order;
struct folio_iter fi;
char *kaddr;
int ret;
/* Compressed data length, can be unaligned */
@@ -350,8 +370,15 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
u32 cur_in = 0;
/* Bytes decompressed so far */
u32 cur_out = 0;
/* The current folio index number inside the bio. */
u32 cur_folio_index = 0;
kaddr = kmap_local_folio(cb->compressed_folios[0], 0);
bio_first_folio(&fi, &cb->bbio.bio, 0);
/* There must be a compressed folio and matches the sectorsize. */
if (unlikely(!fi.folio))
return -EINVAL;
ASSERT(folio_size(fi.folio) == sectorsize);
kaddr = kmap_local_folio(fi.folio, 0);
len_in = read_compress_length(kaddr);
kunmap_local(kaddr);
cur_in += LZO_LEN;
@@ -388,7 +415,7 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
*/
ASSERT(cur_in / sectorsize ==
(cur_in + LZO_LEN - 1) / sectorsize);
cur_folio = cb->compressed_folios[cur_in >> min_folio_shift];
cur_folio = get_current_folio(cb, &fi, &cur_folio_index, cur_in);
ASSERT(cur_folio);
kaddr = kmap_local_folio(cur_folio, 0);
seg_len = read_compress_length(kaddr + offset_in_folio(cur_folio, cur_in));
@@ -410,7 +437,8 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
}
/* Copy the compressed segment payload into workspace */
copy_compressed_segment(cb, workspace->cbuf, seg_len, &cur_in);
copy_compressed_segment(cb, &fi, &cur_folio_index, workspace->cbuf,
seg_len, &cur_in);
/* Decompress the data */
ret = lzo1x_decompress_safe(workspace->cbuf, seg_len,