Commit df0e91d4 authored Feb 08, 2018 by Miklos Szeredi

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: 6ff958ed ("fuse: add atomic open+truncate support")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>

parent c698ca52

fs/fuse/dir.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

Admin message