From: Kent Overstreet <kent.overstreet@linux.dev>
To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-bcachefs@vger.kernel.org
Cc: Kent Overstreet <kent.overstreet@gmail.com>,
Kent Overstreet <kent.overstreet@linux.dev>,
Jan Kara <jack@suse.cz>, "Darrick J . Wong" <djwong@kernel.org>
Subject: [PATCH 06/32] sched: Add task_struct->faults_disabled_mapping
Date: Tue, 9 May 2023 12:56:31 -0400 [thread overview]
Message-ID: <20230509165657.1735798-7-kent.overstreet@linux.dev> (raw)
In-Reply-To: <20230509165657.1735798-1-kent.overstreet@linux.dev>
From: Kent Overstreet <kent.overstreet@gmail.com>
This is used by bcachefs to fix a page cache coherency issue with
O_DIRECT writes.
Also relevant: mapping->invalidate_lock, see below.
O_DIRECT writes (and other filesystem operations that modify file data
while bypassing the page cache) need to shoot down ranges of the page
cache - and additionally, need locking to prevent those pages from
pulled back in.
But O_DIRECT writes invoke the page fault handler (via get_user_pages),
and the page fault handler will need to take that same lock - this is a
classic recursive deadlock if userspace has mmaped the file they're DIO
writing to and uses those pages for the buffer to write from, and it's a
lock ordering deadlock in general.
Thus we need a way to signal from the dio code to the page fault handler
when we already are holding the pagecache add lock on an address space -
this patch just adds a member to task_struct for this purpose. For now
only bcachefs is implementing this locking, though it may be moved out
of bcachefs and made available to other filesystems in the future.
---------------------------------
The closest current VFS equivalent is mapping->invalidate_lock, which
comes from XFS. However, it's not used by direct IO. Instead, direct IO
paths shoot down the page cache twice - before starting the IO and at
the end, and they're still technically racy w.r.t. page cache coherency.
This is a more complete approach: in the future we might consider
replacing mapping->invalidate_lock with the bcachefs code.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Jan Kara <jack@suse.cz>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
---
include/linux/sched.h | 1 +
init/init_task.c | 1 +
2 files changed, 2 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 63d242164b..f2a56f64f7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -869,6 +869,7 @@ struct task_struct {
struct mm_struct *mm;
struct mm_struct *active_mm;
+ struct address_space *faults_disabled_mapping;
int exit_state;
int exit_code;
diff --git a/init/init_task.c b/init/init_task.c
index ff6c4b9bfe..f703116e05 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -85,6 +85,7 @@ struct task_struct init_task
.nr_cpus_allowed= NR_CPUS,
.mm = NULL,
.active_mm = &init_mm,
+ .faults_disabled_mapping = NULL,
.restart_block = {
.fn = do_no_restart_syscall,
},
--
2.40.1
next prev parent reply other threads:[~2023-05-09 16:57 UTC|newest]
Thread overview: 207+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-09 16:56 [PATCH 00/32] bcachefs - a new COW filesystem Kent Overstreet
2023-05-09 16:56 ` [PATCH 01/32] Compiler Attributes: add __flatten Kent Overstreet
2023-05-09 17:04 ` Miguel Ojeda
2023-05-09 17:24 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 02/32] locking/lockdep: lock_class_is_held() Kent Overstreet
2023-05-09 19:30 ` Peter Zijlstra
2023-05-09 20:11 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 03/32] locking/lockdep: lockdep_set_no_check_recursion() Kent Overstreet
2023-05-09 19:31 ` Peter Zijlstra
2023-05-09 19:57 ` Kent Overstreet
2023-05-09 20:18 ` Kent Overstreet
2023-05-09 20:27 ` Waiman Long
2023-05-09 20:35 ` Kent Overstreet
2023-05-09 21:37 ` Waiman Long
2023-05-10 8:59 ` Peter Zijlstra
2023-05-10 20:38 ` Kent Overstreet
2023-05-11 8:25 ` Peter Zijlstra
2023-05-11 9:32 ` Kent Overstreet
2023-05-12 20:49 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 04/32] locking: SIX locks (shared/intent/exclusive) Kent Overstreet
2023-05-11 12:14 ` Jan Engelhardt
2023-05-12 20:58 ` Kent Overstreet
2023-05-12 22:39 ` Jan Engelhardt
2023-05-12 23:26 ` Kent Overstreet
2023-05-12 23:49 ` Randy Dunlap
2023-05-13 0:17 ` Kent Overstreet
2023-05-13 0:45 ` Eric Biggers
2023-05-13 0:51 ` Kent Overstreet
2023-05-14 12:15 ` Jeff Layton
2023-05-15 2:39 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 05/32] MAINTAINERS: Add entry for six locks Kent Overstreet
2023-05-09 16:56 ` Kent Overstreet [this message]
2023-05-10 1:07 ` [PATCH 06/32] sched: Add task_struct->faults_disabled_mapping Jan Kara
2023-05-10 6:18 ` Kent Overstreet
2023-05-23 13:34 ` Jan Kara
2023-05-23 13:34 ` [Cluster-devel] " Jan Kara
2023-05-23 16:21 ` Christoph Hellwig
2023-05-23 16:21 ` Christoph Hellwig
2023-05-23 16:35 ` Kent Overstreet
2023-05-23 16:35 ` Kent Overstreet
2023-05-24 6:43 ` Christoph Hellwig
2023-05-24 6:43 ` Christoph Hellwig
2023-05-24 8:09 ` Kent Overstreet
2023-05-24 8:09 ` Kent Overstreet
2023-05-25 8:58 ` Christoph Hellwig
2023-05-25 8:58 ` Christoph Hellwig
2023-05-25 20:50 ` Kent Overstreet
2023-05-25 20:50 ` Kent Overstreet
2023-05-26 8:06 ` Christoph Hellwig
2023-05-26 8:06 ` Christoph Hellwig
2023-05-26 8:34 ` Kent Overstreet
2023-05-26 8:34 ` Kent Overstreet
2023-05-25 21:40 ` Kent Overstreet
2023-05-25 21:40 ` Kent Overstreet
2023-05-25 22:25 ` Andreas Grünbacher
2023-05-25 22:25 ` Andreas Grünbacher
2023-05-25 23:20 ` Kent Overstreet
2023-05-25 23:20 ` Kent Overstreet
2023-05-26 0:05 ` Andreas Grünbacher
2023-05-26 0:05 ` Andreas Grünbacher
2023-05-26 0:39 ` Kent Overstreet
2023-05-26 0:39 ` Kent Overstreet
2023-05-26 8:10 ` Christoph Hellwig
2023-05-26 8:10 ` Christoph Hellwig
2023-05-26 8:38 ` Kent Overstreet
2023-05-26 8:38 ` Kent Overstreet
2023-05-23 16:49 ` Kent Overstreet
2023-05-23 16:49 ` [Cluster-devel] " Kent Overstreet
2023-05-25 8:47 ` Jan Kara
2023-05-25 8:47 ` [Cluster-devel] " Jan Kara
2023-05-25 21:36 ` Kent Overstreet
2023-05-25 21:36 ` [Cluster-devel] " Kent Overstreet
2023-05-25 22:45 ` Andreas Grünbacher
2023-05-25 22:45 ` [Cluster-devel] " Andreas Grünbacher
2023-05-25 22:04 ` Andreas Grünbacher
2023-05-25 22:04 ` [Cluster-devel] " Andreas Grünbacher
2023-05-09 16:56 ` [PATCH 07/32] mm: Bring back vmalloc_exec Kent Overstreet
2023-05-09 18:19 ` Lorenzo Stoakes
2023-05-09 20:15 ` Kent Overstreet
2023-05-09 20:46 ` Christoph Hellwig
2023-05-09 21:12 ` Lorenzo Stoakes
2023-05-09 21:29 ` Kent Overstreet
2023-05-10 6:48 ` Eric Biggers
2023-05-12 18:36 ` Kent Overstreet
2023-05-13 1:57 ` Eric Biggers
2023-05-13 19:28 ` Kent Overstreet
2023-05-14 5:45 ` Kent Overstreet
2023-05-14 18:43 ` Eric Biggers
2023-05-15 5:38 ` Kent Overstreet
2023-05-15 6:13 ` Eric Biggers
2023-05-15 6:18 ` Kent Overstreet
2023-05-15 7:13 ` Eric Biggers
2023-05-15 7:26 ` Kent Overstreet
2023-05-21 21:33 ` Eric Biggers
2023-05-21 22:04 ` Kent Overstreet
2023-05-15 10:29 ` David Laight
2023-05-10 11:56 ` David Laight
2023-05-09 21:43 ` Darrick J. Wong
2023-05-09 21:54 ` Kent Overstreet
2023-05-11 5:33 ` Theodore Ts'o
2023-05-11 5:44 ` Kent Overstreet
2023-05-13 13:25 ` Lorenzo Stoakes
2023-05-14 18:39 ` Christophe Leroy
2023-05-14 23:43 ` Kent Overstreet
2023-05-15 4:45 ` Christophe Leroy
2023-05-15 5:02 ` Kent Overstreet
2023-05-10 14:18 ` Christophe Leroy
2023-05-10 15:05 ` Johannes Thumshirn
2023-05-11 22:28 ` Kees Cook
2023-05-12 18:41 ` Kent Overstreet
2023-05-16 21:02 ` Kees Cook
2023-05-16 21:20 ` Kent Overstreet
2023-05-16 21:47 ` Matthew Wilcox
2023-05-16 21:57 ` Kent Overstreet
2023-05-17 5:28 ` Kent Overstreet
2023-05-17 14:04 ` Mike Rapoport
2023-05-17 14:18 ` Kent Overstreet
2023-05-17 15:44 ` Mike Rapoport
2023-05-17 15:59 ` Kent Overstreet
2023-06-17 4:13 ` Andy Lutomirski
2023-06-17 15:34 ` Kent Overstreet
2023-06-17 19:19 ` Andy Lutomirski
2023-06-17 20:08 ` Kent Overstreet
2023-06-17 20:35 ` Andy Lutomirski
2023-06-19 19:45 ` Kees Cook
2023-06-20 0:39 ` Kent Overstreet
2023-06-19 9:19 ` Mark Rutland
2023-06-19 10:47 ` Kent Overstreet
2023-06-19 12:47 ` Mark Rutland
2023-06-19 19:17 ` Kent Overstreet
2023-06-20 17:42 ` Andy Lutomirski
2023-06-20 18:08 ` Kent Overstreet
2023-06-20 18:15 ` Andy Lutomirski
2023-06-20 18:48 ` Dave Hansen
2023-06-20 20:18 ` Kent Overstreet
2023-06-20 20:42 ` Andy Lutomirski
2023-06-20 22:32 ` Andy Lutomirski
2023-06-20 22:43 ` Nadav Amit
2023-06-21 1:27 ` Andy Lutomirski
2023-05-09 16:56 ` [PATCH 08/32] fs: factor out d_mark_tmpfile() Kent Overstreet
2023-05-09 16:56 ` [PATCH 09/32] block: Add some exports for bcachefs Kent Overstreet
2023-05-09 16:56 ` [PATCH 10/32] block: Allow bio_iov_iter_get_pages() with bio->bi_bdev unset Kent Overstreet
2023-05-09 16:56 ` [PATCH 11/32] block: Bring back zero_fill_bio_iter Kent Overstreet
2023-05-09 16:56 ` [PATCH 12/32] block: Rework bio_for_each_segment_all() Kent Overstreet
2023-05-09 16:56 ` [PATCH 13/32] block: Rework bio_for_each_folio_all() Kent Overstreet
2023-05-09 16:56 ` [PATCH 14/32] block: Don't block on s_umount from __invalidate_super() Kent Overstreet
2023-05-09 16:56 ` [PATCH 15/32] bcache: move closures to lib/ Kent Overstreet
2023-05-10 1:10 ` Randy Dunlap
2023-05-09 16:56 ` [PATCH 16/32] MAINTAINERS: Add entry for closures Kent Overstreet
2023-05-09 17:05 ` Coly Li
2023-05-09 21:03 ` Randy Dunlap
2023-05-09 16:56 ` [PATCH 17/32] closures: closure_wait_event() Kent Overstreet
2023-05-09 16:56 ` [PATCH 18/32] closures: closure_nr_remaining() Kent Overstreet
2023-05-09 16:56 ` [PATCH 19/32] closures: Add a missing include Kent Overstreet
2023-05-09 16:56 ` [PATCH 20/32] vfs: factor out inode hash head calculation Kent Overstreet
2023-05-23 9:27 ` (subset) " Christian Brauner
2023-05-23 22:53 ` Dave Chinner
2023-05-24 6:44 ` Christoph Hellwig
2023-05-24 7:35 ` Dave Chinner
2023-05-24 8:31 ` Christian Brauner
2023-05-24 8:41 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 21/32] hlist-bl: add hlist_bl_fake() Kent Overstreet
2023-05-10 4:48 ` Dave Chinner
2023-05-23 9:27 ` (subset) " Christian Brauner
2023-05-09 16:56 ` [PATCH 22/32] vfs: inode cache conversion to hash-bl Kent Overstreet
2023-05-10 4:45 ` Dave Chinner
2023-05-16 15:45 ` Christian Brauner
2023-05-16 16:17 ` Kent Overstreet
2023-05-16 23:15 ` Dave Chinner
2023-05-22 13:04 ` Christian Brauner
2023-05-23 9:28 ` (subset) " Christian Brauner
2023-10-19 15:30 ` Mateusz Guzik
2023-10-19 15:59 ` Mateusz Guzik
2023-10-20 11:38 ` Dave Chinner
2023-10-20 17:49 ` Mateusz Guzik
2023-10-21 12:13 ` Mateusz Guzik
2023-10-23 5:10 ` Dave Chinner
2023-10-27 17:13 ` Mateusz Guzik
2023-10-27 18:36 ` Darrick J. Wong
2023-10-31 11:02 ` Christian Brauner
2023-10-31 11:31 ` Mateusz Guzik
2023-11-02 2:36 ` Kent Overstreet
2023-11-04 20:51 ` Dave Chinner
2023-05-09 16:56 ` [PATCH 23/32] iov_iter: copy_folio_from_iter_atomic() Kent Overstreet
2023-05-10 2:20 ` kernel test robot
2023-05-11 2:08 ` kernel test robot
2023-05-09 16:56 ` [PATCH 24/32] MAINTAINERS: Add entry for generic-radix-tree Kent Overstreet
2023-05-09 21:03 ` Randy Dunlap
2023-05-09 16:56 ` [PATCH 25/32] lib/generic-radix-tree.c: Don't overflow in peek() Kent Overstreet
2023-05-09 16:56 ` [PATCH 26/32] lib/generic-radix-tree.c: Add a missing include Kent Overstreet
2023-05-09 16:56 ` [PATCH 27/32] lib/generic-radix-tree.c: Add peek_prev() Kent Overstreet
2023-05-09 16:56 ` [PATCH 28/32] stacktrace: Export stack_trace_save_tsk Kent Overstreet
2023-06-19 9:10 ` Mark Rutland
2023-06-19 11:16 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 29/32] lib/string_helpers: string_get_size() now returns characters wrote Kent Overstreet
2023-07-12 19:58 ` Kees Cook
2023-07-12 20:19 ` Kent Overstreet
2023-07-12 22:38 ` Kees Cook
2023-07-12 23:53 ` Kent Overstreet
2023-07-12 20:23 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 30/32] lib: Export errname Kent Overstreet
2023-05-09 16:56 ` [PATCH 31/32] lib: add mean and variance module Kent Overstreet
2023-05-09 16:56 ` [PATCH 32/32] MAINTAINERS: Add entry for bcachefs Kent Overstreet
2023-05-09 21:04 ` Randy Dunlap
2023-05-09 21:07 ` Kent Overstreet
2023-06-15 20:41 ` [PATCH 00/32] bcachefs - a new COW filesystem Pavel Machek
2023-06-15 21:26 ` Kent Overstreet
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