Commit a6452b85 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: prepare zstd to support bs > ps cases 



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: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent c2ffb1ec

fs/btrfs/fs.c

+18 −0
Original line number Diff line number Diff line
@@ -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

fs/btrfs/zstd.c

+16 −14
Original line number Diff line number Diff line
@@ -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;