Commit b7849516 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Carlos Maiolino
Browse files

iomap: move locking out of iomap_write_delalloc_release 



XFS (which currently is the only user of iomap_write_delalloc_release)
already holds invalidate_lock for most zeroing operations.  To be able
to avoid a deadlock it needs to stop taking the lock, but doing so
in iomap would leak XFS locking details into iomap.

To avoid this require the caller to hold invalidate_lock when calling
iomap_write_delalloc_release instead of taking it there.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarCarlos Maiolino <cem@kernel.org>
parent caf0ea45

fs/iomap/buffered-io.c

+8 −9
Original line number Diff line number Diff line
@@ -1211,12 +1211,13 @@ void iomap_write_delalloc_release(struct inode *inode, loff_t start_byte, 
	loff_t scan_end_byte = min(i_size_read(inode), end_byte);



	/*

	 * Lock the mapping to avoid races with page faults re-instantiating

	 * folios and dirtying them via ->page_mkwrite whilst we walk the

	 * cache and perform delalloc extent removal. Failing to do this can

	 * leave dirty pages with no space reservation in the cache.

	 * The caller must hold invalidate_lock to avoid races with page faults

	 * re-instantiating folios and dirtying them via ->page_mkwrite whilst

	 * we walk the cache and perform delalloc extent removal.  Failing to do

	 * this can leave dirty pages with no space reservation in the cache.

	 */

	filemap_invalidate_lock(inode->i_mapping);

	lockdep_assert_held_write(&inode->i_mapping->invalidate_lock);



	while (start_byte < scan_end_byte) {

		loff_t		data_end;
@@ -1233,7 +1234,7 @@ void iomap_write_delalloc_release(struct inode *inode, loff_t start_byte, 
		if (start_byte == -ENXIO || start_byte == scan_end_byte)

			break;

		if (WARN_ON_ONCE(start_byte < 0))

			goto out_unlock;

			return;

		WARN_ON_ONCE(start_byte < punch_start_byte);

		WARN_ON_ONCE(start_byte > scan_end_byte);
@@ -1244,7 +1245,7 @@ void iomap_write_delalloc_release(struct inode *inode, loff_t start_byte, 
		data_end = mapping_seek_hole_data(inode->i_mapping, start_byte,

				scan_end_byte, SEEK_HOLE);

		if (WARN_ON_ONCE(data_end < 0))

			goto out_unlock;

			return;



		/*

		 * If we race with post-direct I/O invalidation of the page cache,
@@ -1266,8 +1267,6 @@ void iomap_write_delalloc_release(struct inode *inode, loff_t start_byte, 
	if (punch_start_byte < end_byte)

		punch(inode, punch_start_byte, end_byte - punch_start_byte,

				iomap);

out_unlock:

	filemap_invalidate_unlock(inode->i_mapping);

}

EXPORT_SYMBOL_GPL(iomap_write_delalloc_release);

fs/xfs/xfs_iomap.c

+2 −0
Original line number Diff line number Diff line
@@ -1239,8 +1239,10 @@ xfs_buffered_write_iomap_end( 
	if (start_byte >= end_byte)

		return 0;



	filemap_invalidate_lock(inode->i_mapping);

	iomap_write_delalloc_release(inode, start_byte, end_byte, flags, iomap,

			xfs_buffered_write_delalloc_punch);

	filemap_invalidate_unlock(inode->i_mapping);

	return 0;

}