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authorJan Kara <jack@suse.cz>2015-11-30 10:15:42 -0700
committerJens Axboe <axboe@fb.com>2015-11-30 10:15:42 -0700
commit74cedf9b6c603f2278a05bc91b140b32b434d0b5 (patch)
tree0d4412cee169295a290867b72545b65c742527a8
parentbf4e6b4e757488dee1b6a581f49c7ac34cd217f8 (diff)
direct-io: Fix negative return from dio read beyond eof
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: stable@vger.kernel.org CC: Steven Whitehouse <swhiteho@redhat.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--fs/direct-io.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c
index cb5337d8c273..1c75a3a07f8f 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1169,6 +1169,15 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
}
}
+ /* 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.
@@ -1222,7 +1231,6 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
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;