4.9-stable review patch. If anyone has any objections, please let me know.
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From: Miklos Szeredi mszeredi@redhat.com
commit df0e91d488276086bc07da2e389986cae0048c37 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/fuse/dir.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
--- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1633,8 +1633,19 @@ int fuse_do_setattr(struct dentry *dentr 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; }