fuse: atomic_o_trunc should truncate pagecache
Fuse has an "atomic_o_trunc" mode, where userspace filesystem uses the
O_TRUNC flag in the OPEN request to truncate the file atomically with the
open.
In this mode there's no need to send a SETATTR request to userspace after
the open, so fuse_do_setattr() checks this mode and returns. But this
misses the important step of truncating the pagecache.
Add the missing parts of truncation to the ATTR_OPEN branch.
Reported-by: Chad Austin <chadaustin@fb.com>
Fixes: 6ff958edbf39 ("fuse: add atomic open+truncate support")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 2496738..7a980b44 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1629,8 +1629,19 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
return err;
if (attr->ia_valid & ATTR_OPEN) {
- if (fc->atomic_o_trunc)
+ /* This is coming from open(..., ... | O_TRUNC); */
+ WARN_ON(!(attr->ia_valid & ATTR_SIZE));
+ WARN_ON(attr->ia_size != 0);
+ if (fc->atomic_o_trunc) {
+ /*
+ * No need to send request to userspace, since actual
+ * truncation has already been done by OPEN. But still
+ * need to truncate page cache.
+ */
+ i_size_write(inode, 0);
+ truncate_pagecache(inode, 0);
return 0;
+ }
file = NULL;
}