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ovl: punt write aio completion to workqueue

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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>
This commit is contained in:
Amir Goldstein 2023-08-22 20:50:59 +03:00
parent 5f034d3473
commit 389a4a4a19
2 changed files with 42 additions and 1 deletions
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42
fs/overlayfs/file.c
View file

@ -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;
@ -305,6 +310,37 @@ 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;
@ -404,6 +440,10 @@ 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)
@ -412,7 +452,7 @@ 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);

1
fs/super.c
View file

@ -2157,3 +2157,4 @@ int sb_init_dio_done_wq(struct super_block *sb)
destroy_workqueue(wq);
return 0;
}
EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);