From: Christoph Hellwig <hch@lst.de>
To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Waiman Long <longman@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-ext4@vger.kernel.org, cluster-devel@redhat.com
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 07/12] iomap: allow holding i_rwsem until aio completion
Date: Tue, 14 Jan 2020 17:12:20 +0100 [thread overview]
Message-ID: <20200114161225.309792-8-hch@lst.de> (raw)
In-Reply-To: <20200114161225.309792-1-hch@lst.de>
The direct I/O code currently uses a hand crafted i_dio_count that needs
to be incremented under i_rwsem and then is decremented when I/O
completes. That scheme means file system code needs to be very careful
to wait for i_dio_count to reach zero under i_rwsem in various places
that are very cumbersome to get rid. It also means we can't get the
effect of an exclusive i_rwsem for actually asynchronous I/O, forcing
pointless synchronous execution of sub-blocksize writes.
Replace the i_dio_count scheme with holding i_rwsem over the duration
of the whole I/O. While this introduces a non-owner unlock that isn't
nice to RT workload, the open coded locking primitive using i_dio_count
isn't any better.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/iomap/direct-io.c | 44 +++++++++++++++++++++++++++++++++++++------
include/linux/iomap.h | 2 ++
2 files changed, 40 insertions(+), 6 deletions(-)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index e706329d71a0..0113ac33b0a0 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -70,7 +70,7 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
dio->submit.cookie = submit_bio(bio);
}
-static ssize_t iomap_dio_complete(struct iomap_dio *dio)
+static ssize_t iomap_dio_complete(struct iomap_dio *dio, bool unlock)
{
const struct iomap_dio_ops *dops = dio->dops;
struct kiocb *iocb = dio->iocb;
@@ -112,6 +112,13 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
dio_warn_stale_pagecache(iocb->ki_filp);
}
+ if (unlock) {
+ if (dio->flags & IOMAP_DIO_RWSEM_EXCL)
+ up_write(&inode->i_rwsem);
+ else if (dio->flags & IOMAP_DIO_RWSEM_SHARED)
+ up_read(&inode->i_rwsem);
+ }
+
/*
* If this is a DSYNC write, make sure we push it to stable storage now
* that we've written data.
@@ -129,8 +136,22 @@ static void iomap_dio_complete_work(struct work_struct *work)
{
struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
struct kiocb *iocb = dio->iocb;
+ struct inode *inode = file_inode(iocb->ki_filp);
- iocb->ki_complete(iocb, iomap_dio_complete(dio), 0);
+ /*
+ * XXX: For reads this code is directly called from bio ->end_io, which
+ * often is hard or softirq context. In that case lockdep records the
+ * below as lock acquisitions from irq context and causes warnings.
+ */
+ if (dio->flags & IOMAP_DIO_RWSEM_EXCL) {
+ rwsem_acquire(&inode->i_rwsem.dep_map, 0, 0, _THIS_IP_);
+ if (IS_ENABLED(CONFIG_RWSEM_SPIN_ON_OWNER))
+ atomic_long_set(&inode->i_rwsem.owner, (long)current);
+ } else if (dio->flags & IOMAP_DIO_RWSEM_SHARED) {
+ rwsem_acquire_read(&inode->i_rwsem.dep_map, 0, 0, _THIS_IP_);
+ }
+
+ iocb->ki_complete(iocb, iomap_dio_complete(dio, true), 0);
}
/*
@@ -430,7 +451,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio->i_size = i_size_read(inode);
dio->dops = dops;
dio->error = 0;
- dio->flags = 0;
+ dio->flags = dio_flags;
dio->submit.iter = iter;
dio->submit.waiter = current;
@@ -551,8 +572,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio->wait_for_completion = wait_for_completion;
if (!atomic_dec_and_test(&dio->ref)) {
if (!wait_for_completion)
- return -EIOCBQUEUED;
-
+ goto async_completion;
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!READ_ONCE(dio->submit.waiter))
@@ -567,10 +587,22 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
__set_current_state(TASK_RUNNING);
}
- return iomap_dio_complete(dio);
+ return iomap_dio_complete(dio, false);
out_free_dio:
kfree(dio);
return ret;
+
+async_completion:
+ /*
+ * We are returning to userspace now, but i_rwsem is still held until
+ * the I/O completion comes back.
+ */
+ if (dio_flags & (IOMAP_DIO_RWSEM_EXCL | IOMAP_DIO_RWSEM_SHARED))
+ rwsem_release(&inode->i_rwsem.dep_map, _THIS_IP_);
+ if ((dio_flags & IOMAP_DIO_RWSEM_EXCL) &&
+ IS_ENABLED(CONFIG_RWSEM_SPIN_ON_OWNER))
+ atomic_long_set(&inode->i_rwsem.owner, RWSEM_OWNER_UNKNOWN);
+ return -EIOCBQUEUED;
}
EXPORT_SYMBOL_GPL(iomap_dio_rw);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 3faeb8fd0961..f259bb979d7f 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -249,6 +249,8 @@ int iomap_writepages(struct address_space *mapping,
#define IOMAP_DIO_UNWRITTEN (1 << 0) /* covers unwritten extent(s) */
#define IOMAP_DIO_COW (1 << 1) /* covers COW extent(s) */
#define IOMAP_DIO_SYNCHRONOUS (1 << 2) /* no async completion */
+#define IOMAP_DIO_RWSEM_EXCL (1 << 3) /* holds shared i_rwsem */
+#define IOMAP_DIO_RWSEM_SHARED (1 << 4) /* holds exclusive i_rwsem */
struct iomap_dio_ops {
int (*end_io)(struct kiocb *iocb, ssize_t size, int error,
--
2.24.1
next prev parent reply other threads:[~2020-01-14 16:13 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-14 16:12 RFC: hold i_rwsem until aio completes Christoph Hellwig
2020-01-14 16:12 ` [PATCH 01/12] mm: fix a comment in sys_swapon Christoph Hellwig
2020-02-10 23:29 ` Andrew Morton
2020-02-12 7:37 ` Christoph Hellwig
2020-01-14 16:12 ` [PATCH 02/12] locking/rwsem: Exit early when held by an anonymous owner Christoph Hellwig
2020-01-14 18:17 ` Waiman Long
2020-01-14 18:25 ` Christoph Hellwig
2020-01-14 18:33 ` Waiman Long
2020-01-14 18:55 ` Waiman Long
2020-01-14 16:12 ` [PATCH 03/12] xfs: fix IOCB_NOWAIT handling in xfs_file_dio_aio_read Christoph Hellwig
2020-01-14 16:12 ` [PATCH 04/12] gfs2: move setting current->backing_dev_info Christoph Hellwig
2020-01-14 16:12 ` [PATCH 05/12] gfs2: fix O_SYNC write handling Christoph Hellwig
2020-02-06 15:31 ` [Cluster-devel] " Andreas Gruenbacher
2020-01-14 16:12 ` [PATCH 06/12] iomap: pass a flags value to iomap_dio_rw Christoph Hellwig
2020-01-14 16:12 ` Christoph Hellwig [this message]
2020-01-14 16:12 ` [PATCH 08/12] ext4: hold i_rwsem until AIO completes Christoph Hellwig
2020-01-14 21:50 ` Theodore Y. Ts'o
2020-01-15 6:48 ` Christoph Hellwig
2020-01-14 16:12 ` [PATCH 09/12] gfs2: " Christoph Hellwig
2020-01-14 16:12 ` [PATCH 10/12] xfs: " Christoph Hellwig
2020-01-14 16:12 ` [PATCH 11/12] xfs: don't set IOMAP_DIO_SYNCHRONOUS for unaligned I/O Christoph Hellwig
2020-01-14 16:12 ` [PATCH 12/12] iomap: remove the inode_dio_begin/end calls Christoph Hellwig
2020-01-14 18:47 ` RFC: hold i_rwsem until aio completes Matthew Wilcox
2020-01-15 6:54 ` Christoph Hellwig
2020-01-14 19:27 ` Jason Gunthorpe
2020-01-15 6:56 ` Christoph Hellwig
2020-01-15 13:24 ` Jason Gunthorpe
2020-01-15 14:33 ` Peter Zijlstra
2020-01-15 14:49 ` Jason Gunthorpe
2020-01-15 19:03 ` Waiman Long
2020-01-15 19:07 ` Christoph Hellwig
2020-01-18 22:40 ` Matthew Wilcox
2020-01-15 15:36 ` Christoph Hellwig
2020-01-15 16:26 ` Jason Gunthorpe
2020-01-16 14:00 ` Jan Kara
2020-02-03 17:44 ` Christoph Hellwig
2020-01-18 9:28 ` Dave Chinner
2020-02-03 17:46 ` Christoph Hellwig
2020-02-03 23:02 ` Dave Chinner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200114161225.309792-8-hch@lst.de \
--to=hch@lst.de \
--cc=akpm@linux-foundation.org \
--cc=cluster-devel@redhat.com \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-xfs@vger.kernel.org \
--cc=longman@redhat.com \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).