Revert "btrfs: zstd: fix and simplify the inline extent decompression"

This reverts commit 1e7f6def8b2370ecefb54b3c8f390ff894b0c51b.

It causes my machine to not even boot, and Klara Modin reports that the
cause is that small zstd-compressed files return garbage when read.

Reported-by: Klara Modin <klarasmodin@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CABq1_vj4GpUeZpVG49OHCo-3sdbe2-2ROcu_xDvUG-6-5zPRXg@mail.gmail.com/
Reported-and-bisected-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: David Sterba <dsterba@suse.com>
Cc: Qu Wenruo <wqu@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 97fe3ebf11a223455bfa315709991947cf39ead5..afd7e50d073d4ac743c924b70e7e1734af2f6ffc 100644 (file)
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -169,7 +169,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                unsigned long *total_in, unsigned long *total_out);
 int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
 int zstd_decompress(struct list_head *ws, const u8 *data_in,
-               struct page *dest_page, unsigned long dest_pgoff, size_t srclen,
+               struct page *dest_page, unsigned long start_byte, size_t srclen,
                size_t destlen);
 void zstd_init_workspace_manager(void);
 void zstd_cleanup_workspace_manager(void);

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 346c46d88d07f89dcb647a374ee5cd4e57a32c77..0d66db8bc1d4774835348a1aa71b827371aebb65 100644 (file)
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -20,7 +20,6 @@
 #include "misc.h"
 #include "compression.h"
 #include "ctree.h"
-#include "super.h"
 
 #define ZSTD_BTRFS_MAX_WINDOWLOG 17
 #define ZSTD_BTRFS_MAX_INPUT (1 << ZSTD_BTRFS_MAX_WINDOWLOG)
@@ -619,48 +618,80 @@ done:
 }
 
 int zstd_decompress(struct list_head *ws, const u8 *data_in,
-               struct page *dest_page, unsigned long dest_pgoff, size_t srclen,
+               struct page *dest_page, unsigned long start_byte, size_t srclen,
                size_t destlen)
 {
        struct workspace *workspace = list_entry(ws, struct workspace, list);
-       struct btrfs_fs_info *fs_info = btrfs_sb(dest_page->mapping->host->i_sb);
-       const u32 sectorsize = fs_info->sectorsize;
        zstd_dstream *stream;
        int ret = 0;
-       unsigned long to_copy = 0;
+       size_t ret2;
+       unsigned long total_out = 0;
+       unsigned long pg_offset = 0;
 
        stream = zstd_init_dstream(
                        ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
        if (!stream) {
                pr_warn("BTRFS: zstd_init_dstream failed\n");
+               ret = -EIO;
                goto finish;
        }
 
+       destlen = min_t(size_t, destlen, PAGE_SIZE);
+
        workspace->in_buf.src = data_in;
        workspace->in_buf.pos = 0;
        workspace->in_buf.size = srclen;
 
        workspace->out_buf.dst = workspace->buf;
        workspace->out_buf.pos = 0;
-       workspace->out_buf.size = sectorsize;
-
-       /*
-        * Since both input and output buffers should not exceed one sector,
-        * one call should end the decompression.
-        */
-       ret = zstd_decompress_stream(stream, &workspace->out_buf, &workspace->in_buf);
-       if (zstd_is_error(ret)) {
-               pr_warn_ratelimited("BTRFS: zstd_decompress_stream return %d\n",
-                                   zstd_get_error_code(ret));
-               goto finish;
+       workspace->out_buf.size = PAGE_SIZE;
+
+       ret2 = 1;
+       while (pg_offset < destlen
+              && workspace->in_buf.pos < workspace->in_buf.size) {
+               unsigned long buf_start;
+               unsigned long buf_offset;
+               unsigned long bytes;
+
+               /* Check if the frame is over and we still need more input */
+               if (ret2 == 0) {
+                       pr_debug("BTRFS: zstd_decompress_stream ended early\n");
+                       ret = -EIO;
+                       goto finish;
+               }
+               ret2 = zstd_decompress_stream(stream, &workspace->out_buf,
+                               &workspace->in_buf);
+               if (zstd_is_error(ret2)) {
+                       pr_debug("BTRFS: zstd_decompress_stream returned %d\n",
+                                       zstd_get_error_code(ret2));
+                       ret = -EIO;
+                       goto finish;
+               }
+
+               buf_start = total_out;
+               total_out += workspace->out_buf.pos;
+               workspace->out_buf.pos = 0;
+
+               if (total_out <= start_byte)
+                       continue;
+
+               if (total_out > start_byte && buf_start < start_byte)
+                       buf_offset = start_byte - buf_start;
+               else
+                       buf_offset = 0;
+
+               bytes = min_t(unsigned long, destlen - pg_offset,
+                               workspace->out_buf.size - buf_offset);
+
+               memcpy_to_page(dest_page, pg_offset,
+                              workspace->out_buf.dst + buf_offset, bytes);
+
+               pg_offset += bytes;
        }
-       to_copy = workspace->out_buf.pos;
-       memcpy_to_page(dest_page, dest_pgoff + to_copy, workspace->out_buf.dst, to_copy);
+       ret = 0;
 finish:
-       /* Error or early end. */
-       if (unlikely(to_copy < destlen)) {
-               ret = -EIO;
-               memzero_page(dest_page, dest_pgoff + to_copy, destlen - to_copy);
+       if (pg_offset < destlen) {
+               memzero_page(dest_page, pg_offset, destlen - pg_offset);
        }
        return ret;
 }