Patch "fuse: direct-io: don't dirty ITER_BVEC pages" has been added to the 4.4-stable tree

Patch "fuse: direct-io: don't dirty ITER_BVEC pages" has been added to the 4.4-stable tree

[gregkh]

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

    fuse: direct-io: don't dirty ITER_BVEC pages

to the 4.4-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:
     fuse-direct-io-don-t-dirty-iter_bvec-pages.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 8fba54aebbdf1f999738121922e74bf796ad60ee Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Wed, 24 Aug 2016 18:17:04 +0200
Subject: fuse: direct-io: don't dirty ITER_BVEC pages

From: Miklos Szeredi <mszeredi@redhat.com>

commit 8fba54aebbdf1f999738121922e74bf796ad60ee upstream.

When reading from a loop device backed by a fuse file it deadlocks on
lock_page().

This is because the page is already locked by the read() operation done on
the loop device.  In this case we don't want to either lock the page or
dirty it.

So do what fs/direct-io.c does: only dirty the page for ITER_IOVEC vectors.

Reported-by: Sheng Yang <sheng@yasker.org>
Fixes: aa4d86163e4e ("block: loop: switch to VFS ITER_BVEC")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Sheng Yang <sheng@yasker.org>
Reviewed-by: Ashish Samant <ashish.samant@oracle.com>
Tested-by: Sheng Yang <sheng@yasker.org>
Tested-by: Ashish Samant <ashish.samant@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/fuse/file.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -540,13 +540,13 @@ void fuse_read_fill(struct fuse_req *req
 	req->out.args[0].size = count;
 }
 
-static void fuse_release_user_pages(struct fuse_req *req, int write)
+static void fuse_release_user_pages(struct fuse_req *req, bool should_dirty)
 {
 	unsigned i;
 
 	for (i = 0; i < req->num_pages; i++) {
 		struct page *page = req->pages[i];
-		if (write)
+		if (should_dirty)
 			set_page_dirty_lock(page);
 		put_page(page);
 	}
@@ -1331,6 +1331,7 @@ ssize_t fuse_direct_io(struct fuse_io_pr
 		       loff_t *ppos, int flags)
 {
 	int write = flags & FUSE_DIO_WRITE;
+	bool should_dirty = !write && iter_is_iovec(iter);
 	int cuse = flags & FUSE_DIO_CUSE;
 	struct file *file = io->file;
 	struct inode *inode = file->f_mapping->host;
@@ -1375,7 +1376,7 @@ ssize_t fuse_direct_io(struct fuse_io_pr
 			nres = fuse_send_read(req, io, pos, nbytes, owner);
 
 		if (!io->async)
-			fuse_release_user_pages(req, !write);
+			fuse_release_user_pages(req, should_dirty);
 		if (req->out.h.error) {
 			if (!res)
 				res = req->out.h.error;


Patches currently in stable-queue which might be from mszeredi@redhat.com are

queue-4.4/fuse-direct-io-don-t-dirty-iter_bvec-pages.patch