Commit df2d6f26 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Al Viro
Browse files

fs: always maintain i_dio_count 



Maintain i_dio_count for all filesystems, not just those using DIO_LOCKING.
This these filesystems to also protect truncate against direct I/O requests
by using common code.  Right now the only non-DIO_LOCKING filesystem that
appears to do so is XFS, which uses an opencoded variant of the i_dio_count
scheme.

Behaviour doesn't change for filesystems never calling inode_dio_wait.
For ext4 behaviour changes when using the dioread_nonlock option, which
previously was missing any protection between truncate and direct I/O reads.
For ocfs2 that handcrafted i_dio_count manipulations are replaced with
the common code now enable.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 562c72aa

fs/direct-io.c

+13 −12
Original line number Diff line number Diff line
@@ -297,7 +297,6 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is 
		aio_complete(dio->iocb, ret, 0);

	}



	if (dio->flags & DIO_LOCKING)

	inode_dio_done(dio->inode);

	return ret;

}
@@ -1185,14 +1184,16 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, 
 *    For writes this function is called under i_mutex and returns with

 *    i_mutex held, for reads, i_mutex is not held on entry, but it is

 *    taken and dropped again before returning.

 *    The i_dio_count counter keeps track of the number of outstanding

 *    direct I/O requests, and truncate waits for it to reach zero.

 *    New references to i_dio_count must only be grabbed with i_mutex

 *    held.

 *

 *  - if the flags value does NOT contain DIO_LOCKING we don't use any

 *    internal locking but rather rely on the filesystem to synchronize

 *    direct I/O reads/writes versus each other and truncate.

 *

 * To help with locking against truncate we incremented the i_dio_count

 * counter before starting direct I/O, and decrement it once we are done.

 * Truncate can wait for it to reach zero to provide exclusion.  It is

 * expected that filesystem provide exclusion between new direct I/O

 * and truncates.  For DIO_LOCKING filesystems this is done by i_mutex,

 * but other filesystems need to take care of this on their own.

 */

ssize_t

__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
@@ -1270,12 +1271,12 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, 
				goto out;

			}

		}

	}



	/*

	 * Will be decremented at I/O completion time.

	 */

	atomic_inc(&inode->i_dio_count);

	}



	/*

	 * For file extending writes updating i_size before data

fs/ocfs2/aops.c

+1 −3
Original line number Diff line number Diff line
@@ -567,10 +567,8 @@ static void ocfs2_dio_end_io(struct kiocb *iocb, 
	/* this io's submitter should not have unlocked this before we could */

	BUG_ON(!ocfs2_iocb_is_rw_locked(iocb));



	if (ocfs2_iocb_is_sem_locked(iocb)) {

		inode_dio_done(inode);

	if (ocfs2_iocb_is_sem_locked(iocb))

		ocfs2_iocb_clear_sem_locked(iocb);

	}



	ocfs2_iocb_clear_rw_locked(iocb);

fs/ocfs2/file.c

+3 −9
Original line number Diff line number Diff line
@@ -2240,7 +2240,6 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb, 
relock:

	/* to match setattr's i_mutex -> rw_lock ordering */

	if (direct_io) {

		atomic_inc(&inode->i_dio_count);

		have_alloc_sem = 1;

		/* communicate with ocfs2_dio_end_io */

		ocfs2_iocb_set_sem_locked(iocb);
@@ -2292,7 +2291,6 @@ relock: 
	 */

	if (direct_io && !can_do_direct) {

		ocfs2_rw_unlock(inode, rw_level);

		inode_dio_done(inode);



		have_alloc_sem = 0;

		rw_level = -1;
@@ -2379,10 +2377,8 @@ out: 
		ocfs2_rw_unlock(inode, rw_level);



out_sems:

	if (have_alloc_sem) {

		inode_dio_done(inode);

	if (have_alloc_sem)

		ocfs2_iocb_clear_sem_locked(iocb);

	}



	mutex_unlock(&inode->i_mutex);
@@ -2533,7 +2529,6 @@ static ssize_t ocfs2_file_aio_read(struct kiocb *iocb, 
	 */

	if (filp->f_flags & O_DIRECT) {

		have_alloc_sem = 1;

		atomic_inc(&inode->i_dio_count);

		ocfs2_iocb_set_sem_locked(iocb);



		ret = ocfs2_rw_lock(inode, 0);
@@ -2575,10 +2570,9 @@ static ssize_t ocfs2_file_aio_read(struct kiocb *iocb, 
	}



bail:

	if (have_alloc_sem) {

		inode_dio_done(inode);

	if (have_alloc_sem)

		ocfs2_iocb_clear_sem_locked(iocb);

	}



	if (rw_level != -1)

		ocfs2_rw_unlock(inode, rw_level);

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