Commit 7cc91126 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
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fuse: fix parallel dio write on file open in passthrough mode 



Parallel dio write takes a negative refcount of fi->iocachectr and so does
open of file in passthrough mode.

The refcount of passthrough mode is associated with attach/detach of a
fuse_backing object to fuse inode.

For parallel dio write, the backing file is irrelevant, so the call to
fuse_inode_uncached_io_start() passes a NULL fuse_backing object.

Passing a NULL fuse_backing will result in false -EBUSY error if the file
is already open in passthrough mode.

Allow taking negative fi->iocachectr refcount with NULL fuse_backing,
because it does not conflict with an already attached fuse_backing object.

Fixes: 4a90451b ("fuse: implement open in passthrough mode")
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 4864a6dd

fs/fuse/iomode.c

+2 −2
Original line number Diff line number Diff line
@@ -90,7 +90,7 @@ int fuse_inode_uncached_io_start(struct fuse_inode *fi, struct fuse_backing *fb) 
	spin_lock(&fi->lock);

	/* deny conflicting backing files on same fuse inode */

	oldfb = fuse_inode_backing(fi);

	if (oldfb && oldfb != fb) {

	if (fb && oldfb && oldfb != fb) {

		err = -EBUSY;

		goto unlock;

	}
@@ -101,7 +101,7 @@ int fuse_inode_uncached_io_start(struct fuse_inode *fi, struct fuse_backing *fb) 
	fi->iocachectr--;



	/* fuse inode holds a single refcount of backing file */

	if (!oldfb) {

	if (fb && !oldfb) {

		oldfb = fuse_inode_backing_set(fi, fb);

		WARN_ON_ONCE(oldfb != NULL);

	} else {