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btrfs: prepare zstd to support bs > ps cases

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This involves converting the following functions to use proper folio
sizes/shifts:

- zstd_compress_folios()
- zstd_decompress_bio()

The function zstd_decompress() is already using block size correctly
without using page size, thus it needs no modification.

And since zstd compression is calling kmap_local_folio(), the existing
code cannot handle large folios with HIGHMEM, as kmap_local_folio()
requires us to handle one page range each time.

I do not really think it's worth to spend time on some feature that will
be deprecated eventually.  So here just add an extra explicit rejection
for bs > ps with HIGHMEM feature enabled kernels.

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 2025-09-08 16:28:16 +09:30 committed by David Sterba
parent c2ffb1ec1a
commit a6452b85b3
2 changed files with 34 additions and 14 deletions
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18
fs/btrfs/fs.c
View File

@ -79,6 +79,24 @@ bool __attribute_const__ btrfs_supported_blocksize(u32 blocksize)
if (blocksize == PAGE_SIZE || blocksize == SZ_4K || blocksize == BTRFS_MIN_BLOCKSIZE)
return true;
#ifdef CONFIG_BTRFS_EXPERIMENTAL
/*
* For bs > ps support it's done by specifying a minimal folio order
* for filemap, thus implying large data folios.
* For HIGHMEM systems, we can not always access the content of a (large)
* folio in one go, but go through them page by page.
*
* A lot of features don't implement a proper PAGE sized loop for large
* folios, this includes:
*
* - compression
* - verity
* - encoded write
*
* Considering HIGHMEM is such a pain to deal with and it's going
* to be deprecated eventually, just reject HIGHMEM && bs > ps cases.
*/
if (IS_ENABLED(CONFIG_HIGHMEM) && blocksize > PAGE_SIZE)
return false;
if (blocksize <= PAGE_SIZE)
return true;
#endif

30
fs/btrfs/zstd.c
View File

@ -414,7 +414,8 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
const unsigned long nr_dest_folios = *out_folios;
const u64 orig_end = start + len;
const u32 blocksize = fs_info->sectorsize;
unsigned long max_out = nr_dest_folios * PAGE_SIZE;
const u32 min_folio_size = btrfs_min_folio_size(fs_info);
unsigned long max_out = nr_dest_folios * min_folio_size;
unsigned int cur_len;
workspace->params = zstd_get_btrfs_parameters(workspace->req_level, len);
@ -452,7 +453,7 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
folios[nr_folios++] = out_folio;
workspace->out_buf.dst = folio_address(out_folio);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
workspace->out_buf.size = min_t(size_t, max_out, min_folio_size);
while (1) {
size_t ret2;
@ -486,8 +487,8 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
/* Check if we need more output space */
if (workspace->out_buf.pos == workspace->out_buf.size) {
tot_out += PAGE_SIZE;
max_out -= PAGE_SIZE;
tot_out += min_folio_size;
max_out -= min_folio_size;
if (nr_folios == nr_dest_folios) {
ret = -E2BIG;
goto out;
@ -500,8 +501,7 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
folios[nr_folios++] = out_folio;
workspace->out_buf.dst = folio_address(out_folio);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out,
PAGE_SIZE);
workspace->out_buf.size = min_t(size_t, max_out, min_folio_size);
}
/* We've reached the end of the input */
@ -551,8 +551,8 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
goto out;
}
tot_out += PAGE_SIZE;
max_out -= PAGE_SIZE;
tot_out += min_folio_size;
max_out -= min_folio_size;
if (nr_folios == nr_dest_folios) {
ret = -E2BIG;
goto out;
@ -565,7 +565,7 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
folios[nr_folios++] = out_folio;
workspace->out_buf.dst = folio_address(out_folio);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
workspace->out_buf.size = min_t(size_t, max_out, min_folio_size);
}
if (tot_out >= tot_in) {
@ -587,14 +587,16 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
{
struct btrfs_fs_info *fs_info = cb_to_fs_info(cb);
struct workspace *workspace = list_entry(ws, struct workspace, list);
struct folio **folios_in = cb->compressed_folios;
size_t srclen = cb->compressed_len;
zstd_dstream *stream;
int ret = 0;
const u32 blocksize = cb_to_fs_info(cb)->sectorsize;
const u32 blocksize = fs_info->sectorsize;
const unsigned int min_folio_size = btrfs_min_folio_size(fs_info);
unsigned long folio_in_index = 0;
unsigned long total_folios_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
unsigned long total_folios_in = DIV_ROUND_UP(srclen, min_folio_size);
unsigned long buf_start;
unsigned long total_out = 0;
@ -612,7 +614,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
workspace->in_buf.src = kmap_local_folio(folios_in[folio_in_index], 0);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
workspace->in_buf.size = min_t(size_t, srclen, min_folio_size);
workspace->out_buf.dst = workspace->buf;
workspace->out_buf.pos = 0;
@ -657,11 +659,11 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
ret = -EIO;
goto done;
}
srclen -= PAGE_SIZE;
srclen -= min_folio_size;
workspace->in_buf.src =
kmap_local_folio(folios_in[folio_in_index], 0);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
workspace->in_buf.size = min_t(size_t, srclen, min_folio_size);
}
}
ret = 0;