[PATCH 3/5] fuse: add FOPEN_INVAL_ATTR

[Jiachen Zhang]

Add FOPEN_INVAL_ATTR so that the fuse daemon can ask kernel to invalidate
the attr cache on file open.

The fi->attr_version should be increased when handling FOPEN_INVAL_ATTR.
Because if a FUSE request returning attributes (getattr, setattr, lookup,
and readdirplus) starts before a FUSE_OPEN replying FOPEN_INVAL_ATTR, but
finishes after the FUSE_OPEN, staled attributes will be set to the inode
and falsely clears the inval_mask.

Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@xxxxxxxxxxxxx>
---
 fs/fuse/file.c            | 10 ++++++++++
 include/uapi/linux/fuse.h |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index de37a3a06a71..412824a11b7b 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -215,6 +215,16 @@ void fuse_finish_open(struct inode *inode, struct file *file)
 		file_update_time(file);
 		fuse_invalidate_attr_mask(inode, FUSE_STATX_MODSIZE);
 	}
+
+	if (ff->open_flags & FOPEN_INVAL_ATTR) {
+		struct fuse_inode *fi = get_fuse_inode(inode);
+
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
+		fuse_invalidate_attr(inode);
+		spin_unlock(&fi->lock);
+	}
+
 	if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
 		fuse_link_write_file(file);
 }
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index b3fcab13fcd3..1a24c11637a4 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -315,6 +315,7 @@ struct fuse_file_lock {
  * FOPEN_STREAM: the file is stream-like (no file position at all)
  * FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE)
  * FOPEN_PARALLEL_DIRECT_WRITES: Allow concurrent direct writes on the same inode
+ * FOPEN_INVAL_ATTR: invalidate the attr cache on open
  */
 #define FOPEN_DIRECT_IO		(1 << 0)
 #define FOPEN_KEEP_CACHE	(1 << 1)
@@ -323,6 +324,7 @@ struct fuse_file_lock {
 #define FOPEN_STREAM		(1 << 4)
 #define FOPEN_NOFLUSH		(1 << 5)
 #define FOPEN_PARALLEL_DIRECT_WRITES	(1 << 6)
+#define FOPEN_INVAL_ATTR	(1 << 7)
 
 /**
  * INIT request/reply flags
-- 
2.20.1