Commit 8e4473bb authored by Xiubo Li's avatar Xiubo Li Committed by Ilya Dryomov
Browse files

ceph: do not execute direct write in parallel if O_APPEND is specified 



In O_APPEND & O_DIRECT mode, the data from different writers will
be possibly overlapping each other since they take the shared lock.

For example, both Writer1 and Writer2 are in O_APPEND and O_DIRECT
mode:

          Writer1                         Writer2

     shared_lock()                   shared_lock()
     getattr(CAP_SIZE)               getattr(CAP_SIZE)
     iocb->ki_pos = EOF              iocb->ki_pos = EOF
     write(data1)
                                     write(data2)
     shared_unlock()                 shared_unlock()

The data2 will overlap the data1 from the same file offset, the
old EOF.

Switch to exclusive lock instead when O_APPEND is specified.

Signed-off-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent bb6d3fb3

fs/ceph/file.c

+11 −6
Original line number Diff line number Diff line
@@ -1418,6 +1418,7 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from) 
	struct ceph_cap_flush *prealloc_cf;

	ssize_t count, written = 0;

	int err, want, got;

	bool direct_lock = false;

	loff_t pos;

	loff_t limit = max(i_size_read(inode), fsc->max_file_size);
@@ -1428,8 +1429,11 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from) 
	if (!prealloc_cf)

		return -ENOMEM;



	if ((iocb->ki_flags & (IOCB_DIRECT | IOCB_APPEND)) == IOCB_DIRECT)

		direct_lock = true;



retry_snap:

	if (iocb->ki_flags & IOCB_DIRECT)

	if (direct_lock)

		ceph_start_io_direct(inode);

	else

		ceph_start_io_write(inode);
@@ -1519,14 +1523,15 @@ retry_snap: 


		/* we might need to revert back to that point */

		data = *from;

		if (iocb->ki_flags & IOCB_DIRECT) {

		if (iocb->ki_flags & IOCB_DIRECT)

			written = ceph_direct_read_write(iocb, &data, snapc,

							 &prealloc_cf);

			ceph_end_io_direct(inode);

		} else {

		else

			written = ceph_sync_write(iocb, &data, pos, snapc);

		if (direct_lock)

			ceph_end_io_direct(inode);

		else

			ceph_end_io_write(inode);

		}

		if (written > 0)

			iov_iter_advance(from, written);

		ceph_put_snap_context(snapc);
@@ -1577,7 +1582,7 @@ retry_snap: 


	goto out_unlocked;

out:

	if (iocb->ki_flags & IOCB_DIRECT)

	if (direct_lock)

		ceph_end_io_direct(inode);

	else

		ceph_end_io_write(inode);

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