| From 74cedf9b6c603f2278a05bc91b140b32b434d0b5 Mon Sep 17 00:00:00 2001 |
| From: Jan Kara <jack@suse.cz> |
| Date: Mon, 30 Nov 2015 10:15:42 -0700 |
| Subject: direct-io: Fix negative return from dio read beyond eof |
| |
| From: Jan Kara <jack@suse.cz> |
| |
| commit 74cedf9b6c603f2278a05bc91b140b32b434d0b5 upstream. |
| |
| Assume a filesystem with 4KB blocks. When a file has size 1000 bytes and |
| we issue direct IO read at offset 1024, blockdev_direct_IO() reads the |
| tail of the last block and the logic for handling short DIO reads in |
| dio_complete() results in a return value -24 (1000 - 1024) which |
| obviously confuses userspace. |
| |
| Fix the problem by bailing out early once we sample i_size and can |
| reliably check that direct IO read starts beyond i_size. |
| |
| Reported-by: Avi Kivity <avi@scylladb.com> |
| Fixes: 9fe55eea7e4b444bafc42fa0000cc2d1d2847275 |
| CC: Steven Whitehouse <swhiteho@redhat.com> |
| Signed-off-by: Jan Kara <jack@suse.cz> |
| Signed-off-by: Jens Axboe <axboe@fb.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/direct-io.c | 10 +++++++++- |
| 1 file changed, 9 insertions(+), 1 deletion(-) |
| |
| --- a/fs/direct-io.c |
| +++ b/fs/direct-io.c |
| @@ -1161,6 +1161,15 @@ do_blockdev_direct_IO(struct kiocb *iocb |
| } |
| } |
| |
| + /* Once we sampled i_size check for reads beyond EOF */ |
| + dio->i_size = i_size_read(inode); |
| + if (iov_iter_rw(iter) == READ && offset >= dio->i_size) { |
| + if (dio->flags & DIO_LOCKING) |
| + mutex_unlock(&inode->i_mutex); |
| + kmem_cache_free(dio_cache, dio); |
| + goto out; |
| + } |
| + |
| /* |
| * For file extending writes updating i_size before data writeouts |
| * complete can expose uninitialized blocks in dumb filesystems. |
| @@ -1214,7 +1223,6 @@ do_blockdev_direct_IO(struct kiocb *iocb |
| sdio.next_block_for_io = -1; |
| |
| dio->iocb = iocb; |
| - dio->i_size = i_size_read(inode); |
| |
| spin_lock_init(&dio->bio_lock); |
| dio->refcount = 1; |
