[BUG]
There is a recent bug that btrfs/012 fails and kernel rejects to read a
symbolic link which is backed by a regular extent.
Furthremore in that case, "btrfs check --mode=lowmem" doesn't detect such
problem at all.
[CAUSE]
For symbolic links, we only allow inline extents, and this means we should
only have a symbolic link target which is smaller than 4K.
But lowmem mode btrfs check doesn't handle symbolic link inodes any
differently, thus it doesn't check if the file extents are inlined or not,
nor reporting this problem as an error.
[FIX]
When processing data extents, if we find the owning inode is a symbolic
link, and the file extent is regular/preallocated, report an error for
the bad file extent item.
Signed-off-by: Qu Wenruo <wqu@suse.com>
6674a952ff