Commit f9a49aa3 authored by Joanne Koong's avatar Joanne Koong Committed by Andrew Morton
Browse files

fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes() 

Above the while() loop in wait_sb_inodes(), we document that we must wait
for all pages under writeback for data integrity.  Consequently, if a
mapping, like fuse, traditionally does not have data integrity semantics,
there is no need to wait at all; we can simply skip these inodes.

This restores fuse back to prior behavior where syncs are no-ops.  This
fixes a user regression where if a system is running a faulty fuse server
that does not reply to issued write requests, this causes wait_sb_inodes()
to wait forever.

Link: https://lkml.kernel.org/r/20260105211737.4105620-2-joannelkoong@gmail.com


Fixes: 0c58a97f ("fuse: remove tmp folio for writebacks and internal rb tree")
Signed-off-by: default avatarJoanne Koong <joannelkoong@gmail.com>
Reported-by: default avatarAthul Krishna <athul.krishna.kr@protonmail.com>
Reported-by: default avatarJ. Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-by: default avatarBernd Schubert <bschubert@ddn.com>
Tested-by: default avatarJ. Neuschäfer <j.neuschaefer@gmx.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Bernd Schubert <bschubert@ddn.com>
Cc: Bonaccorso Salvatore <carnil@debian.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent be31340a

fs/fs-writeback.c

+6 −1
Original line number Diff line number Diff line
@@ -2750,8 +2750,13 @@ static void wait_sb_inodes(struct super_block *sb) 
		 * The mapping can appear untagged while still on-list since we

		 * do not have the mapping lock. Skip it here, wb completion

		 * will remove it.

		 *

		 * If the mapping does not have data integrity semantics,

		 * there's no need to wait for the writeout to complete, as the

		 * mapping cannot guarantee that data is persistently stored.

		 */

		if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))

		if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK) ||

		    mapping_no_data_integrity(mapping))

			continue;



		spin_unlock_irq(&sb->s_inode_wblist_lock);

fs/fuse/file.c

+3 −1
Original line number Diff line number Diff line
@@ -3200,8 +3200,10 @@ void fuse_init_file_inode(struct inode *inode, unsigned int flags) 


	inode->i_fop = &fuse_file_operations;

	inode->i_data.a_ops = &fuse_file_aops;

	if (fc->writeback_cache)

	if (fc->writeback_cache) {

		mapping_set_writeback_may_deadlock_on_reclaim(&inode->i_data);

		mapping_set_no_data_integrity(&inode->i_data);

	}



	INIT_LIST_HEAD(&fi->write_files);

	INIT_LIST_HEAD(&fi->queued_writes);

include/linux/pagemap.h

+11 −0
Original line number Diff line number Diff line
@@ -210,6 +210,7 @@ enum mapping_flags { 
	AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,

	AS_KERNEL_FILE = 10,	/* mapping for a fake kernel file that shouldn't

				   account usage to user cgroups */

	AS_NO_DATA_INTEGRITY = 11, /* no data integrity guarantees */

	/* Bits 16-25 are used for FOLIO_ORDER */

	AS_FOLIO_ORDER_BITS = 5,

	AS_FOLIO_ORDER_MIN = 16,
@@ -345,6 +346,16 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres 
	return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);

}



static inline void mapping_set_no_data_integrity(struct address_space *mapping)

{

	set_bit(AS_NO_DATA_INTEGRITY, &mapping->flags);

}



static inline bool mapping_no_data_integrity(const struct address_space *mapping)

{

	return test_bit(AS_NO_DATA_INTEGRITY, &mapping->flags);

}



static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)

{

	return mapping->gfp_mask;