From: Andreas Gruenbacher <agruenba@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>,
"Darrick J. Wong" <djwong@kernel.org>
Cc: Jan Kara <jack@suse.cz>, Matthew Wilcox <willy@infradead.org>,
cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com,
Andreas Gruenbacher <agruenba@redhat.com>
Subject: [PATCH v3 7/7] gfs2: Fix mmap + page fault deadlocks for direct I/O
Date: Fri, 23 Jul 2021 22:58:40 +0200 [thread overview]
Message-ID: <20210723205840.299280-8-agruenba@redhat.com> (raw)
In-Reply-To: <20210723205840.299280-1-agruenba@redhat.com>
Also disable page faults during direct I/O requests and implement the same kind
of retry logic as in the buffered I/O case.
Direct I/O requests differ from buffered I/O requests in that they use
bio_iov_iter_get_pages for grabbing page references and faulting in pages
instead of triggering real page faults. Those manual page faults can be
disabled with the iocb->noio flag.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/gfs2/file.c | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 insertions(+), 1 deletion(-)
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index f66ac7f56f6d..7986f3be69d2 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -782,21 +782,41 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to,
struct file *file = iocb->ki_filp;
struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
size_t count = iov_iter_count(to);
+ size_t written = 0;
ssize_t ret;
+ /*
+ * In this function, we disable page faults when we're holding the
+ * inode glock while doing I/O. If a page fault occurs, we drop the
+ * inode glock, fault in the pages manually, and then we retry. Other
+ * than in gfs2_file_read_iter, iomap_dio_rw can trigger implicit as
+ * well as manual page faults, and we need to disable both kinds
+ * separately.
+ */
+
if (!count)
return 0; /* skip atime */
gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, gh);
+retry:
ret = gfs2_glock_nq(gh);
if (ret)
goto out_uninit;
+ pagefault_disable();
+ to->noio = true;
ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL, 0);
+ to->noio = false;
+ pagefault_enable();
+
gfs2_glock_dq(gh);
+ if (ret > 0)
+ written += ret;
+ if (unlikely(ret == -EFAULT) && fault_in_iov_iter(to))
+ goto retry;
out_uninit:
gfs2_holder_uninit(gh);
- return ret;
+ return written ? written : ret;
}
static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
@@ -809,6 +829,12 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
loff_t offset = iocb->ki_pos;
ssize_t ret;
+ /*
+ * In this function, we disable page faults when we're holding the
+ * inode glock while doing I/O. If a page fault occurs, we drop the
+ * inode glock, fault in the pages manually, and then we retry.
+ */
+
/*
* Deferred lock, even if its a write, since we do no allocation on
* this path. All we need to change is the atime, and this lock mode
@@ -818,6 +844,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
* VFS does.
*/
gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, gh);
+retry:
ret = gfs2_glock_nq(gh);
if (ret)
goto out_uninit;
@@ -826,11 +853,16 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
if (offset + len > i_size_read(&ip->i_inode))
goto out;
+ from->noio = true;
ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL, 0);
+ from->noio = false;
+
if (ret == -ENOTBLK)
ret = 0;
out:
gfs2_glock_dq(gh);
+ if (unlikely(ret == -EFAULT) && fault_in_iov_iter(from))
+ goto retry;
out_uninit:
gfs2_holder_uninit(gh);
return ret;
--
2.26.3
next prev parent reply other threads:[~2021-07-23 20:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 20:58 [PATCH v3 0/7] gfs2: Fix mmap + page fault deadlocks Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 1/7] iov_iter: Introduce fault_in_iov_iter helper Andreas Gruenbacher
2021-07-23 23:40 ` Linus Torvalds
2021-07-24 7:51 ` Andreas Grünbacher
2021-07-24 1:52 ` Al Viro
2021-07-24 8:05 ` Andreas Grünbacher
2021-07-26 16:33 ` Jan Kara
2021-07-26 17:15 ` Linus Torvalds
2021-07-23 20:58 ` [PATCH v3 2/7] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 3/7] gfs2: Fix mmap + page fault deadlocks for buffered I/O Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 4/7] iomap: Fix iomap_dio_rw return value for user copies Andreas Gruenbacher
2021-07-23 20:58 ` [PATCH v3 5/7] iomap: Support restarting direct I/O requests after user copy failures Andreas Gruenbacher
2021-07-26 17:19 ` Jan Kara
[not found] ` <CAHpGcMLtQ1=WOT1mTUS4=iWBwHLQ-EBzY=+XuSGJfu4gVPYTLw@mail.gmail.com>
2021-07-26 18:08 ` Jan Kara
2021-07-23 20:58 ` [PATCH v3 6/7] iov_iter: Introduce noio flag to disable page faults Andreas Gruenbacher
2021-07-23 20:58 ` Andreas Gruenbacher [this message]
2021-07-26 17:02 ` [PATCH v3 7/7] gfs2: Fix mmap + page fault deadlocks for direct I/O Jan Kara
[not found] ` <CAHpGcMLOZhZ7tGrY7rcYWUwx12sY884T=eC-Ckna63PBmF=zwA@mail.gmail.com>
2021-07-26 18:00 ` Jan Kara
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