[PATCH 4.9 35/62] fuse: truncate pending writes on O_TRUNC

Greg Kroah-Hartman
2019-11-04T21:50:47Z

From: Miklos Szeredi <mszeredi@redhat.com>

commit e4648309b85a78f8c787457832269a8712a8673e upstream.

Make sure cached writes are not reordered around open(..., O_TRUNC), with
the obvious wrong results.

Fixes: 4d99ff8f12eb ("fuse: Turn writeback cache on")
Cc: <stable@vger.kernel.org> # v3.15+
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/fuse/file.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -201,7 +201,7 @@ int fuse_open_common(struct inode *inode
{
struct fuse_conn *fc = get_fuse_conn(inode);
int err;
- bool lock_inode = (file->f_flags & O_TRUNC) &&
+ bool is_wb_truncate = (file->f_flags & O_TRUNC) &&
fc->atomic_o_trunc &&
fc->writeback_cache;

@@ -209,16 +209,20 @@ int fuse_open_common(struct inode *inode
if (err)
return err;

- if (lock_inode)
+ if (is_wb_truncate) {
inode_lock(inode);
+ fuse_set_nowrite(inode);
+ }

err = fuse_do_open(fc, get_node_id(inode), file, isdir);

if (!err)
fuse_finish_open(inode, file);

- if (lock_inode)
+ if (is_wb_truncate) {
+ fuse_release_nowrite(inode);
inode_unlock(inode);
+ }

return err;
}