From: Amir Goldstein <amir73il@gmail.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
Christian Brauner <brauner@kernel.org>,
linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org
Subject: [PATCH] ovl: punt write aio completion to workqueue
Date: Thu, 28 Sep 2023 09:46:36 +0300 [thread overview]
Message-ID: <20230928064636.487317-1-amir73il@gmail.com> (raw)
We want to protect concurrent updates of ovl inode size and mtime
(i.e. ovl_copyattr()) from aio completion context.
Punt write aio completion to a workqueue so that we can protect
ovl_copyattr() with a spinlock.
Export sb_init_dio_done_wq(), so that overlayfs can use its own
dio workqueue to punt aio completions.
Suggested-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/8620dfd3-372d-4ae0-aa3f-2fe97dda1bca@kernel.dk/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
Hi Jens,
I did not want to add an overlayfs specific workqueue for those
completions, because, as I'd mentioned before, I intend to move this
stacked file io infrastructure to common vfs code.
I figured it's fine for overlayfs (or any stacked filesystem) to use its
own s_dio_done_wq for its own private needs.
Please help me reassure that I got this right.
Thanks,
Amir.
fs/overlayfs/file.c | 42 +++++++++++++++++++++++++++++++++++++++++-
fs/super.c | 1 +
2 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 173cc55e47fb..b4fefd96881f 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -15,10 +15,15 @@
#include <linux/fs.h>
#include "overlayfs.h"
+#include "../internal.h" /* for sb_init_dio_done_wq */
+
struct ovl_aio_req {
struct kiocb iocb;
refcount_t ref;
struct kiocb *orig_iocb;
+ /* used for aio completion */
+ struct work_struct work;
+ long res;
};
static struct kmem_cache *ovl_aio_request_cachep;
@@ -302,6 +307,37 @@ static void ovl_aio_rw_complete(struct kiocb *iocb, long res)
orig_iocb->ki_complete(orig_iocb, res);
}
+static void ovl_aio_complete_work(struct work_struct *work)
+{
+ struct ovl_aio_req *aio_req = container_of(work,
+ struct ovl_aio_req, work);
+
+ ovl_aio_rw_complete(&aio_req->iocb, aio_req->res);
+}
+
+static void ovl_aio_queue_completion(struct kiocb *iocb, long res)
+{
+ struct ovl_aio_req *aio_req = container_of(iocb,
+ struct ovl_aio_req, iocb);
+ struct kiocb *orig_iocb = aio_req->orig_iocb;
+
+ /*
+ * Punt to a work queue to serialize updates of mtime/size.
+ */
+ aio_req->res = res;
+ INIT_WORK(&aio_req->work, ovl_aio_complete_work);
+ queue_work(file_inode(orig_iocb->ki_filp)->i_sb->s_dio_done_wq,
+ &aio_req->work);
+}
+
+static int ovl_init_aio_done_wq(struct super_block *sb)
+{
+ if (sb->s_dio_done_wq)
+ return 0;
+
+ return sb_init_dio_done_wq(sb);
+}
+
static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
@@ -402,6 +438,10 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
} else {
struct ovl_aio_req *aio_req;
+ ret = ovl_init_aio_done_wq(inode->i_sb);
+ if (ret)
+ goto out;
+
ret = -ENOMEM;
aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
if (!aio_req)
@@ -411,7 +451,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
aio_req->orig_iocb = iocb;
kiocb_clone(&aio_req->iocb, iocb, get_file(real.file));
aio_req->iocb.ki_flags = ifl;
- aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+ aio_req->iocb.ki_complete = ovl_aio_queue_completion;
refcount_set(&aio_req->ref, 2);
kiocb_start_write(&aio_req->iocb);
ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
diff --git a/fs/super.c b/fs/super.c
index 2d762ce67f6e..6ab6624989f2 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -2139,3 +2139,4 @@ int sb_init_dio_done_wq(struct super_block *sb)
destroy_workqueue(wq);
return 0;
}
+EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);
--
2.34.1
next reply other threads:[~2023-09-28 6:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-28 6:46 Amir Goldstein [this message]
2023-09-28 7:08 ` [PATCH] ovl: punt write aio completion to workqueue Jens Axboe
2023-09-28 9:15 ` Amir Goldstein
2023-09-28 9:22 ` Matthew Wilcox
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