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Patch "ceph: only dirty ITER_IOVEC pages for direct read" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message Apr 1, 2018

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This is a note to let you know that I've just added the patch titled

ceph: only dirty ITER_IOVEC pages for direct read

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ceph-only-dirty-iter_iovec-pages-for-direct-read.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 85784f9395987a422fa04263e7c0fb13da11eb5c Mon Sep 17 00:00:00 2001

From: "Yan, Zheng" <[email protected]>
Date: Fri, 16 Mar 2018 11:22:29 +0800
Subject: ceph: only dirty ITER_IOVEC pages for direct read

From: Yan, Zheng <[email protected]>

commit 85784f9395987a422fa04263e7c0fb13da11eb5c upstream.

If a page is already locked, attempting to dirty it leads to a deadlock in lock_page(). This is what currently happens to ITER_BVEC pages when a dio-enabled loop device is backed by ceph:

  $ losetup --direct-io /dev/loop0 /mnt/cephfs/img
  $ xfs_io -c 'pread 0 4k' /dev/loop0

Follow other file systems and only dirty ITER_IOVEC pages.

Cc [email protected]
Signed-off-by "Yan, Zheng" <[email protected]>
Reviewed-by Ilya Dryomov <[email protected]>
Signed-off-by Ilya Dryomov <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 fs/ceph/file.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
fs/ceph/file.c +6 -3
@@ -598,7 +598,8 @@ static ssize_t ceph_sync_read(struct kio
 struct ceph_aio_request {
 	struct kiocb *iocb;
 	size_t total_len;
-	int write;
+	bool write;
+	bool should_dirty;
 	int error;
 	struct list_head osd_reqs;
 	unsigned num_reqs;

@@ -708,7 +709,7 @@ static void ceph_aio_complete_req(struct
 		}
 	}
 
-	ceph_put_page_vector(osd_data->pages, num_pages, !aio_req->write);
+	ceph_put_page_vector(osd_data->pages, num_pages, aio_req->should_dirty);
 	ceph_osdc_put_request(req);
 
 	if (rc < 0)

@@ -890,6 +891,7 @@ ceph_direct_read_write(struct kiocb *ioc
 	size_t count = iov_iter_count(iter);
 	loff_t pos = iocb->ki_pos;
 	bool write = iov_iter_rw(iter) == WRITE;
+	bool should_dirty = !write && iter_is_iovec(iter);
 
 	if (write && ceph_snap(file_inode(file)) != CEPH_NOSNAP)
 		return -EROFS;

@@ -954,6 +956,7 @@ ceph_direct_read_write(struct kiocb *ioc
 			if (aio_req) {
 				aio_req->iocb = iocb;
 				aio_req->write = write;
+				aio_req->should_dirty = should_dirty;
 				INIT_LIST_HEAD(&aio_req->osd_reqs);
 				if (write) {
 					aio_req->mtime = mtime;

@@ -1012,7 +1015,7 @@ ceph_direct_read_write(struct kiocb *ioc
 				len = ret;
 		}
 
-		ceph_put_page_vector(pages, num_pages, !write);
+		ceph_put_page_vector(pages, num_pages, should_dirty);
 
 		ceph_osdc_put_request(req);
 		if (ret < 0)

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ceph-only-dirty-iter_iovec-pages-for-direct-read.patch