deny partial write for loop dev fd

Partial write can be easily supported by LO_CRYPT_NONE mode, but it is not
easy in LO_CRYPT_CRYPTOAPI case, because of its block nature.  I don't know
who still used cryptoapi, but theoretically it is possible.  So let's leave
things as they are.  Loop device doesn't support partial write before
Nick's "write_begin/write_end" patch set, and let's it behave the same way
after.

Signed-off-by: Dmitriy Monakhov <dmonakhov@openvz.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 3 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index a5f993ac28dd..e5a051577a5e 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -245,10 +245,8 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
 
                 ret = pagecache_write_end(file, mapping, pos, size, copied,
                                                         page, fsdata);
-                if (ret < 0)
+                if (ret < 0 || ret != copied)
                         goto fail;
-                if (ret < copied)
-                        copied = ret;
 
                 if (unlikely(transfer_result))
                         goto fail;