Commit 389a4a4a authored by Amir Goldstein's avatar Amir Goldstein
Browse files

ovl: punt write aio completion to workqueue 



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: default avatarJens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/8620dfd3-372d-4ae0-aa3f-2fe97dda1bca@kernel.dk/


Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
parent 5f034d34

fs/overlayfs/file.c

+41 −1
Original line number Diff line number Diff line
@@ -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);

fs/super.c

+1 −0
Original line number Diff line number Diff line
@@ -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);