btrfs: zstd: fix and simplify the inline extent decompression
[BUG] If we have a filesystem with 4k sectorsize, and an inlined compressed extent created like this: item 4 key (257 INODE_ITEM 0) itemoff 15863 itemsize 160 generation 8 transid 8 size 4096 nbytes 4096 block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0 sequence 1 flags 0x0(none) item 5 key (257 INODE_REF 256) itemoff 15839 itemsize 24 index 2 namelen 14 name: source_inlined item 6 key (257 EXTENT_DATA 0) itemoff 15770 itemsize 69 generation 8 type 0 (inline) inline extent data size 48 ram_bytes 4096 compression 3 (zstd) Then trying to reflink that extent in an aarch64 system with 64K page size, the reflink would just fail: # xfs_io -f -c "reflink $mnt/source_inlined 0 60k 4k" $mnt/dest XFS_IOC_CLONE_RANGE: Input/output error [CAUSE] In zstd_decompress(), we didn't treat @start_byte as just a page offset, but also use it as an indicator on whether we should error out, without any proper explanation (this is copied from other decompression code). In reality, for subpage cases, although @start_byte can be non-zero, we should never switch input/output buffer nor error out, since the whole input/output buffer should never exceed one sector, thus we should not need to do any buffer switch. Thus the current code using @start_byte as a condition to switch input/output buffer or finish the decompression is completely incorrect. [FIX] The fix involves several modification: - Rename @start_byte to @dest_pgoff to properly express its meaning - Use @sectorsize other than PAGE_SIZE to properly initialize the output buffer size - Use correct destination offset inside the destination page - Simplify the main loop Since the input/output buffer should never switch, we only need one zstd_decompress_stream() call. - Consider early end as an error After the fix, even on 64K page sized aarch64, above reflink now works as expected: # xfs_io -f -c "reflink $mnt/source_inlined 0 60k 4k" $mnt/dest linked 4096/4096 bytes at offset 61440 And results the correct file layout: item 9 key (258 INODE_ITEM 0) itemoff 15542 itemsize 160 generation 10 transid 10 size 65536 nbytes 4096 block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0 sequence 1 flags 0x0(none) item 10 key (258 INODE_REF 256) itemoff 15528 itemsize 14 index 3 namelen 4 name: dest item 11 key (258 XATTR_ITEM 3817753667) itemoff 15445 itemsize 83 location key (0 UNKNOWN.0 0) type XATTR transid 10 data_len 37 name_len 16 name: security.selinux data unconfined_u:object_r:unlabeled_t:s0 item 12 key (258 EXTENT_DATA 61440) itemoff 15392 itemsize 53 generation 10 type 1 (regular) extent data disk byte 13631488 nr 4096 extent data offset 0 nr 4096 ram 4096 extent compression 0 (none) 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
David Sterba
parent
6a69631ec9
commit
1e7f6def8b
@ -169,7 +169,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
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unsigned long *total_in, unsigned long *total_out);
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int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
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int zstd_decompress(struct list_head *ws, const u8 *data_in,
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struct page *dest_page, unsigned long start_byte, size_t srclen,
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struct page *dest_page, unsigned long dest_pgoff, size_t srclen,
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size_t destlen);
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void zstd_init_workspace_manager(void);
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void zstd_cleanup_workspace_manager(void);
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@ -20,6 +20,7 @@
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#include "misc.h"
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#include "compression.h"
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#include "ctree.h"
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#include "super.h"
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#define ZSTD_BTRFS_MAX_WINDOWLOG 17
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#define ZSTD_BTRFS_MAX_INPUT (1 << ZSTD_BTRFS_MAX_WINDOWLOG)
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@ -618,80 +619,48 @@ done:
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}
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int zstd_decompress(struct list_head *ws, const u8 *data_in,
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struct page *dest_page, unsigned long start_byte, size_t srclen,
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struct page *dest_page, unsigned long dest_pgoff, size_t srclen,
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size_t destlen)
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{
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struct workspace *workspace = list_entry(ws, struct workspace, list);
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struct btrfs_fs_info *fs_info = btrfs_sb(dest_page->mapping->host->i_sb);
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const u32 sectorsize = fs_info->sectorsize;
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zstd_dstream *stream;
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int ret = 0;
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size_t ret2;
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unsigned long total_out = 0;
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unsigned long pg_offset = 0;
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unsigned long to_copy = 0;
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stream = zstd_init_dstream(
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ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
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if (!stream) {
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pr_warn("BTRFS: zstd_init_dstream failed\n");
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ret = -EIO;
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goto finish;
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}
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destlen = min_t(size_t, destlen, PAGE_SIZE);
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workspace->in_buf.src = data_in;
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workspace->in_buf.pos = 0;
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workspace->in_buf.size = srclen;
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workspace->out_buf.dst = workspace->buf;
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workspace->out_buf.pos = 0;
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workspace->out_buf.size = PAGE_SIZE;
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workspace->out_buf.size = sectorsize;
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ret2 = 1;
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while (pg_offset < destlen
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&& workspace->in_buf.pos < workspace->in_buf.size) {
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unsigned long buf_start;
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unsigned long buf_offset;
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unsigned long bytes;
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/* Check if the frame is over and we still need more input */
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if (ret2 == 0) {
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pr_debug("BTRFS: zstd_decompress_stream ended early\n");
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ret = -EIO;
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goto finish;
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}
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ret2 = zstd_decompress_stream(stream, &workspace->out_buf,
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&workspace->in_buf);
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if (zstd_is_error(ret2)) {
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pr_debug("BTRFS: zstd_decompress_stream returned %d\n",
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zstd_get_error_code(ret2));
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ret = -EIO;
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goto finish;
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}
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buf_start = total_out;
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total_out += workspace->out_buf.pos;
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workspace->out_buf.pos = 0;
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if (total_out <= start_byte)
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continue;
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if (total_out > start_byte && buf_start < start_byte)
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buf_offset = start_byte - buf_start;
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else
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buf_offset = 0;
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bytes = min_t(unsigned long, destlen - pg_offset,
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workspace->out_buf.size - buf_offset);
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memcpy_to_page(dest_page, pg_offset,
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workspace->out_buf.dst + buf_offset, bytes);
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pg_offset += bytes;
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/*
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* Since both input and output buffers should not exceed one sector,
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* one call should end the decompression.
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*/
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ret = zstd_decompress_stream(stream, &workspace->out_buf, &workspace->in_buf);
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if (zstd_is_error(ret)) {
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pr_warn_ratelimited("BTRFS: zstd_decompress_stream return %d\n",
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zstd_get_error_code(ret));
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goto finish;
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}
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ret = 0;
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to_copy = workspace->out_buf.pos;
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memcpy_to_page(dest_page, dest_pgoff + to_copy, workspace->out_buf.dst, to_copy);
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finish:
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if (pg_offset < destlen) {
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memzero_page(dest_page, pg_offset, destlen - pg_offset);
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/* Error or early end. */
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if (unlikely(to_copy < destlen)) {
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ret = -EIO;
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memzero_page(dest_page, dest_pgoff + to_copy, destlen - to_copy);
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}
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return ret;
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}
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