Commit c3d4ed1a authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Darrick J. Wong
Browse files

iomap: Allow filesystem to call iomap_dio_complete without i_rwsem 



This is to avoid the deadlock caused in btrfs because of O_DIRECT |
O_DSYNC.

Filesystems such as btrfs require i_rwsem while performing sync on a
file. iomap_dio_rw() is called under i_rw_sem. This leads to a
deadlock because of:

iomap_dio_complete()
  generic_write_sync()
    btrfs_sync_file()

Separate out iomap_dio_complete() from iomap_dio_rw(), so filesystems
can call iomap_dio_complete() after unlocking i_rwsem.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 4595a298

fs/iomap/direct-io.c

+26 −9
Original line number Diff line number Diff line
@@ -76,7 +76,7 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap, 
		dio->submit.cookie = submit_bio(bio);

}



static ssize_t iomap_dio_complete(struct iomap_dio *dio)

ssize_t iomap_dio_complete(struct iomap_dio *dio)

{

	const struct iomap_dio_ops *dops = dio->dops;

	struct kiocb *iocb = dio->iocb;
@@ -130,6 +130,7 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio) 


	return ret;

}

EXPORT_SYMBOL_GPL(iomap_dio_complete);



static void iomap_dio_complete_work(struct work_struct *work)

{
@@ -416,8 +417,8 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length, 
 * Returns -ENOTBLK In case of a page invalidation invalidation failure for

 * writes.  The callers needs to fall back to buffered I/O in this case.

 */

ssize_t

iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,

struct iomap_dio *

__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,

		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,

		bool wait_for_completion)

{
@@ -431,14 +432,14 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, 
	struct iomap_dio *dio;



	if (!count)

		return 0;

		return NULL;



	if (WARN_ON(is_sync_kiocb(iocb) && !wait_for_completion))

		return -EIO;

		return ERR_PTR(-EIO);



	dio = kmalloc(sizeof(*dio), GFP_KERNEL);

	if (!dio)

		return -ENOMEM;

		return ERR_PTR(-ENOMEM);



	dio->iocb = iocb;

	atomic_set(&dio->ref, 1);
@@ -568,7 +569,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, 
	dio->wait_for_completion = wait_for_completion;

	if (!atomic_dec_and_test(&dio->ref)) {

		if (!wait_for_completion)

			return -EIOCBQUEUED;

			return ERR_PTR(-EIOCBQUEUED);



		for (;;) {

			set_current_state(TASK_UNINTERRUPTIBLE);
@@ -584,10 +585,26 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, 
		__set_current_state(TASK_RUNNING);

	}



	return iomap_dio_complete(dio);

	return dio;



out_free_dio:

	kfree(dio);

	return ret;

	if (ret)

		return ERR_PTR(ret);

	return NULL;

}

EXPORT_SYMBOL_GPL(__iomap_dio_rw);



ssize_t

iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,

		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,

		bool wait_for_completion)

{

	struct iomap_dio *dio;



	dio = __iomap_dio_rw(iocb, iter, ops, dops, wait_for_completion);

	if (IS_ERR_OR_NULL(dio))

		return PTR_ERR_OR_ZERO(dio);

	return iomap_dio_complete(dio);

}

EXPORT_SYMBOL_GPL(iomap_dio_rw);

include/linux/iomap.h

+5 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
struct address_space;

struct fiemap_extent_info;

struct inode;

struct iomap_dio;

struct iomap_writepage_ctx;

struct iov_iter;

struct kiocb;
@@ -258,6 +259,10 @@ struct iomap_dio_ops { 
ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,

		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,

		bool wait_for_completion);

struct iomap_dio *__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,

		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,

		bool wait_for_completion);

ssize_t iomap_dio_complete(struct iomap_dio *dio);

int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);



#ifdef CONFIG_SWAP