[PATCH] direct-io: Fix unsigned comparison overflow

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The first write after file create fails to take the direct IO
(Peer-to-Peer) path and falls back to slower software copy. The function
get_more_block() sets 'create' to 0 after comparing 'unsigned long
fs_startblk = 0' with 'long long (i_size_read(dio->inode) - 1) >>
i_blkbits = 0xfffffffffffff'.

Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@xxxxxxx>
---
 fs/direct-io.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 3aafb33..588aa17 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -687,8 +687,8 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
 		 */
 		create = dio->op == REQ_OP_WRITE;
 		if (dio->flags & DIO_SKIP_HOLES) {
-			if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
-							i_blkbits))
+			if ((loff_t)fs_startblk <=
+				((i_size_read(dio->inode) - 1) >> i_blkbits))
 				create = 0;
 		}
 
-- 
2.7.4




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