On Mon, Aug 24, 2020 at 03:54:29PM -0400, Josef Bacik wrote:

On 8/21/20 3:38 AM, Omar Sandoval wrote:

quoted

From: Omar Sandoval <redacted>

There are 4 main cases:

1. Inline extents: we copy the data straight out of the extent buffer.
2. Hole/preallocated extents: we fill in zeroes.
3. Regular, uncompressed extents: we read the sectors we need directly
    from disk.
4. Regular, compressed extents: we read the entire compressed extent
    from disk and indicate what subset of the decompressed extent is in
    the file.

This initial implementation simplifies a few things that can be improved
in the future:

- We hold the inode lock during the operation.
- Cases 1, 3, and 4 allocate temporary memory to read into before
   copying out to userspace.

Signed-off-by: Omar Sandoval <redacted>

<snip>

quoted

+	tmp = kmalloc(count, GFP_NOFS);
+	if (!tmp) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	read_extent_buffer(leaf, tmp, ptr, count);
+	btrfs_free_path(path);

Why not just btrfs_release_path(), you're freeing below anyway.

Oh that's nicer, fixed.

Also a mention that we're explicitly not handling read repairs and backup
copies would be good in the changelog as well.  Thanks,

Josef

Will do, thanks.