[PATCH] vfs: fix readahead(2) on block devices

[Reuben Hawkins <reubenhwk@gmail.com>]

Readahead was factored to call generic_fadvise.  That refactor broke
readahead on block devices.

The fix is to check F_ISFIFO rather than F_ISREG.  It would also work to
not check and let generic_fadvise to do the checking, but then the
generic_fadvise return value would have to be checked and changed from
-ESPIPE to -EINVAL to comply with the readahead(2) man-pages.

Fixes: 3d8f7615319b ("vfs: implement readahead(2) using POSIX_FADV_WILLNEED")
Signed-off-by: Reuben Hawkins <reubenhwk@gmail.com>
---
 mm/readahead.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index 47afbca1d122..877ddcb61c76 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -749,7 +749,7 @@ ssize_t ksys_readahead(int fd, loff_t offset, size_t count)
 	 */
 	ret = -EINVAL;
 	if (!f.file->f_mapping || !f.file->f_mapping->a_ops ||
-	    !S_ISREG(file_inode(f.file)->i_mode))
+	    S_ISFIFO(file_inode(f.file)->i_mode))
 		goto out;
 
 	ret = vfs_fadvise(f.file, offset, count, POSIX_FADV_WILLNEED);
-- 
2.34.1