4.9-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 8b9433eb4de3c26a9226c981c283f9f4896ae030 ]
On a DIO_SKIP_HOLES filesystem, the ->get_block() method is currently
not allowed to create blocks for an empty inode. This confusion comes
from trying to bit shift a negative number, so check the size of the
inode first.
The problem is most visible for hfsplus, because the fallback to
buffered I/O doesn't happen and the write fails with EIO. This is in
part the fault of the module, because it gives a wrong return value on
->get_block(); that will be fixed in a separate patch.
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/direct-io.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 07cc38ec66ca6..fc90f0c33cbe4 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -616,6 +616,7 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
unsigned long fs_count; /* Number of filesystem-sized blocks */
int create;
unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
+ loff_t i_size;
/*
* If there was a memory error and we've overwritten all the
@@ -645,8 +646,8 @@ 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))
+ i_size = i_size_read(dio->inode);
+ if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
create = 0;
}
--
2.19.1
