[PATCH U-boot v2] fs: btrfs: fix the false alert of decompression failure

[Qu Wenruo]

There are some cases where decompressed sectors can have padding zeros.

In kernel code, we have lines to address such situation:

        /*
         * btrfs_getblock is doing a zero on the tail of the page too,
         * but this will cover anything missing from the decompressed
         * data.
         */
        if (bytes < destlen)
                memset(kaddr+bytes, 0, destlen-bytes);
        kunmap_local(kaddr);

But not in U-boot code, thus we have some reports of U-boot failed to
read compressed files in btrfs.

Fix it by doing the same thing of the kernel, for both inline and
regular compressed extents.

Reported-by: Matwey Kornilov <matwey.korni...@gmail.com>
Link: https://bugzilla.suse.com/show_bug.cgi?id=1183717
Fixes: a26a6bedafcf ("fs: btrfs: Introduce btrfs_read_extent_inline() and 
btrfs_read_extent_reg()")
Signed-off-by: Qu Wenruo <w...@suse.com>
---
Changelog:
v2:
- Fix the bug for regular and inline compressed extents
---
 fs/btrfs/inode.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 019d532a1a4b..2c2379303d74 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -390,10 +390,16 @@ int btrfs_read_extent_inline(struct btrfs_path *path,
                           csize);
        ret = btrfs_decompress(btrfs_file_extent_compression(leaf, fi),
                               cbuf, csize, dbuf, dsize);
-       if (ret < 0 || ret != dsize) {
+       if (ret == (u32)-1) {
                ret = -EIO;
                goto out;
        }
+       /*
+        * The compressed part ends before sector boundary, the remaining needs
+        * to be zeroed out.
+        */
+       if (ret < dsize)
+               memset(dbuf + ret, 0, dsize - ret);
        memcpy(dest, dbuf, dsize);
        ret = dsize;
 out:
@@ -494,10 +500,16 @@ int btrfs_read_extent_reg(struct btrfs_path *path,
 
        ret = btrfs_decompress(btrfs_file_extent_compression(leaf, fi), cbuf,
                               csize, dbuf, dsize);
-       if (ret != dsize) {
+       if (ret == (u32)-1) {
                ret = -EIO;
                goto out;
        }
+       /*
+        * The compressed part ends before sector boundary, the remaining needs
+        * to be zeroed out.
+        */
+       if (ret < dsize)
+               memset(dbuf + ret, 0, dsize - ret);
        /* Then copy the needed part */
        memcpy(dest, dbuf + btrfs_file_extent_offset(leaf, fi), len);
        ret = len;
-- 
2.31.1