Unverified Commit 9871938f authored by David Howells's avatar David Howells Committed by Christian Brauner
Browse files

netfs, afs: Fix write skipping in dir/link writepages 



Fix netfs_write_single() and afs_single_writepages() to better handle a
write that would be skipped due to lock contention and WB_SYNC_NONE by
returning 1 from netfs_write_single() if it skipped and making
afs_single_writepages() skip also.  If a skip occurs, the inode must be
re-marked as the VFS may have cleared the mark.

This is really only theoretical for directories in netfs_write_single() as
the only path to that is through afs_single_writepages() that takes the
->validate_lock around it, thereby serialising it.

Fixes: 6dd80936 ("afs: Use netfslib for directories")
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/20260512123404.719402-24-dhowells@redhat.com


cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent ded0c6f1

fs/afs/dir.c

+10 −1
Original line number Diff line number Diff line
@@ -2206,7 +2206,14 @@ int afs_single_writepages(struct address_space *mapping, 
	/* Need to lock to prevent the folio queue and folios from being thrown

	 * away.

	 */

	if (!down_read_trylock(&dvnode->validate_lock)) {

		if (wbc->sync_mode == WB_SYNC_NONE) {

			/* The VFS will have undirtied the inode. */

			netfs_single_mark_inode_dirty(&dvnode->netfs.inode);

			return 0;

		}

		down_read(&dvnode->validate_lock);

	}



	if (is_dir ?

	    test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) :
@@ -2214,6 +2221,8 @@ int afs_single_writepages(struct address_space *mapping, 
		iov_iter_folio_queue(&iter, ITER_SOURCE, dvnode->directory, 0, 0,

				     i_size_read(&dvnode->netfs.inode));

		ret = netfs_writeback_single(mapping, wbc, &iter);

		if (ret == 1)

			ret = 0; /* Skipped write due to lock conflict. */

	}



	up_read(&dvnode->validate_lock);

fs/netfs/write_issue.c

+6 −1
Original line number Diff line number Diff line
@@ -830,6 +830,9 @@ static int netfs_write_folio_single(struct netfs_io_request *wreq, 
 *

 * Write a monolithic, non-pagecache object back to the server and/or

 * the cache.

 *

 * Return: 0 if successful; 1 if skipped due to lock conflict and WB_SYNC_NONE;

 * or a negative error code.

 */

int netfs_writeback_single(struct address_space *mapping,

			   struct writeback_control *wbc,
@@ -846,8 +849,10 @@ int netfs_writeback_single(struct address_space *mapping, 


	if (!mutex_trylock(&ictx->wb_lock)) {

		if (wbc->sync_mode == WB_SYNC_NONE) {

			/* The VFS will have undirtied the inode. */

			netfs_single_mark_inode_dirty(&ictx->inode);

			netfs_stat(&netfs_n_wb_lock_skip);

			return 0;

			return 1;

		}

		netfs_stat(&netfs_n_wb_lock_wait);

		mutex_lock(&ictx->wb_lock);