From: Andreas Gruenbacher <agruenba@redhat.com>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: kvm-ppc@vger.kernel.org, Christoph Hellwig <hch@infradead.org>,
cluster-devel <cluster-devel@redhat.com>, Jan Kara <jack@suse.cz>,
Andreas Gruenbacher <agruenba@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Paul Mackerras <paulus@ozlabs.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-btrfs <linux-btrfs@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] [PATCH v8 00/17] gfs2: Fix mmap + page fault deadlocks
Date: Tue, 26 Oct 2021 11:44:30 +0200 [thread overview]
Message-ID: <20211026094430.3669156-1-agruenba@redhat.com> (raw)
In-Reply-To: <YXeOVZqer+GFBkXO@mit.edu>
Ted,
here's an updated version of Dave Hansen's original commit, but note
that generic/208 won't run on ext4 with data journaling enabled:
$ MOUNT_OPTIONS='-o data=journal' TEST_DIR=/mnt/test TEST_DEV=/dev/vdb ./tests/generic/208
QA output created by 208
208 not run: ext4 data journaling doesn't support O_DIRECT
Thanks,
Andreas
--
Based on commit 998ef75ddb57 ("fs: do not prefault sys_write() user
buffer pages") by Dave Hansen <dave.hansen@linux.intel.com>, but:
* Fix generic_perform_write as well as iomap_write_iter.
* copy_page_from_iter_atomic() doesn't trigger page faults, so there's no need
to disable page faults around it [see commit 9e8c2af96e0d ("callers of
iov_copy_from_user_atomic() don't need pagecache_disable()")].
* If fault_in_iov_iter_readable() fails to fault in the entire buffer,
we still want to read everything up to the fault position. This depends on
commit a6294593e8a1 ("iov_iter: Turn iov_iter_fault_in_readable into
fault_in_iov_iter_readable").
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/iomap/buffered-io.c | 20 +++++++-------------
mm/filemap.c | 20 +++++++-------------
2 files changed, 14 insertions(+), 26 deletions(-)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 1753c26c8e76..d8809cd9ab31 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -744,17 +744,6 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
if (bytes > length)
bytes = length;
- /*
- * Bring in the user page that we'll copy from _first_.
- * Otherwise there's a nasty deadlock on copying from the
- * same page as we're writing to, without it being marked
- * up-to-date.
- */
- if (unlikely(fault_in_iov_iter_readable(i, bytes))) {
- status = -EFAULT;
- break;
- }
-
status = iomap_write_begin(iter, pos, bytes, &page);
if (unlikely(status))
break;
@@ -777,9 +766,14 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
* halfway through, might be a race with munmap,
* might be severe memory pressure.
*/
- if (copied)
+ if (copied) {
bytes = copied;
- goto again;
+ goto again;
+ }
+ if (fault_in_iov_iter_readable(i, bytes) != bytes)
+ goto again;
+ status = -EFAULT;
+ break;
}
pos += status;
written += status;
diff --git a/mm/filemap.c b/mm/filemap.c
index 4dd5edcd39fd..467cdb7d086d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3751,17 +3751,6 @@ ssize_t generic_perform_write(struct file *file,
iov_iter_count(i));
again:
- /*
- * Bring in the user page that we will copy from _first_.
- * Otherwise there's a nasty deadlock on copying from the
- * same page as we're writing to, without it being marked
- * up-to-date.
- */
- if (unlikely(fault_in_iov_iter_readable(i, bytes))) {
- status = -EFAULT;
- break;
- }
-
if (fatal_signal_pending(current)) {
status = -EINTR;
break;
@@ -3794,9 +3783,14 @@ ssize_t generic_perform_write(struct file *file,
* halfway through, might be a race with munmap,
* might be severe memory pressure.
*/
- if (copied)
+ if (copied) {
bytes = copied;
- goto again;
+ goto again;
+ }
+ if (fault_in_iov_iter_readable(i, bytes) != bytes)
+ goto again;
+ status = -EFAULT;
+ break;
}
pos += status;
written += status;
--
2.26.3
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next prev parent reply other threads:[~2021-10-26 9:45 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 13:41 [Ocfs2-devel] [PATCH v8 00/17] gfs2: Fix mmap + page fault deadlocks Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 01/17] iov_iter: Fix iov_iter_get_pages{, _alloc} page fault return value Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 02/17] powerpc/kvm: Fix kvm_use_magic_page Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 03/17] gup: Turn fault_in_pages_{readable, writeable} into fault_in_{readable, writeable} Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 04/17] iov_iter: Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 05/17] iov_iter: Introduce fault_in_iov_iter_writeable Andreas Gruenbacher
2021-10-20 16:25 ` Catalin Marinas
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 06/17] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 07/17] gfs2: Clean up function may_grant Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 08/17] gfs2: Introduce flag for glock holder auto-demotion Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 09/17] gfs2: Move the inode glock locking to gfs2_file_buffered_write Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 10/17] gfs2: Eliminate ip->i_gh Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 11/17] gfs2: Fix mmap + page fault deadlocks for buffered I/O Andreas Gruenbacher
2021-10-19 13:41 ` [Ocfs2-devel] [PATCH v8 12/17] iomap: Fix iomap_dio_rw return value for user copies Andreas Gruenbacher
2021-10-19 13:42 ` [Ocfs2-devel] [PATCH v8 13/17] iomap: Support partial direct I/O on user copy failures Andreas Gruenbacher
2021-10-19 13:42 ` [Ocfs2-devel] [PATCH v8 14/17] iomap: Add done_before argument to iomap_dio_rw Andreas Gruenbacher
2021-10-19 15:51 ` Darrick J. Wong
2021-10-19 19:30 ` Andreas Gruenbacher
2021-10-20 1:57 ` Darrick J. Wong
2021-10-19 13:42 ` [Ocfs2-devel] [PATCH v8 15/17] gup: Introduce FOLL_NOFAULT flag to disable page faults Andreas Gruenbacher
2021-10-19 13:42 ` [Ocfs2-devel] [PATCH v8 16/17] iov_iter: Introduce nofault " Andreas Gruenbacher
2021-10-19 13:42 ` [Ocfs2-devel] [PATCH v8 17/17] gfs2: Fix mmap + page fault deadlocks for direct I/O Andreas Gruenbacher
2021-10-19 15:40 ` [Ocfs2-devel] [PATCH v8 00/17] gfs2: Fix mmap + page fault deadlocks Linus Torvalds
2021-10-19 16:00 ` Bob Peterson
2021-10-20 16:36 ` Catalin Marinas
2021-10-20 20:11 ` Linus Torvalds
2021-10-20 22:44 ` Catalin Marinas
2021-10-21 6:19 ` Linus Torvalds
2021-10-22 18:06 ` Catalin Marinas
2021-10-22 19:22 ` Linus Torvalds
2021-10-25 19:00 ` Andreas Gruenbacher
2021-10-26 18:24 ` Catalin Marinas
2021-10-26 18:50 ` Linus Torvalds
2021-10-26 19:18 ` Linus Torvalds
2021-10-27 19:13 ` Catalin Marinas
2021-10-27 21:14 ` Linus Torvalds
2021-10-28 21:20 ` Catalin Marinas
2021-10-28 21:40 ` Catalin Marinas
2021-10-28 22:15 ` Andreas Grünbacher
2021-10-29 12:50 ` Catalin Marinas
2021-10-28 22:32 ` Linus Torvalds
2021-10-29 17:50 ` Catalin Marinas
2021-10-29 18:47 ` Linus Torvalds
2021-10-25 18:24 ` Andreas Gruenbacher
2021-10-26 5:12 ` Theodore Ts'o
2021-10-26 9:44 ` Andreas Gruenbacher [this message]
2021-10-27 21:21 ` Andreas Gruenbacher
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