fs/9p: remove writeback fid and fix per-file modes

This patch removes the creating of an additional writeback_fid
for opened files.  The patch addresses problems when files
were opened write-only or getattr on files with dirty caches.

This patch also incorporates information about cache behavior
in the fid for every file.  This allows us to reflect cache
behavior from mount flags, open mode, and information from
the server to inform readahead and writeback behavior.

This includes adding support for a 9p semantic that qid.version==0
is used to mark a file as non-cachable which is important for
synthetic files.  This may have a side-effect of not supporting
caching on certain legacy file servers that do not properly set
qid.version.  There is also now a mount flag which can disable
the qid.version behavior.

Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

1 files changed, 32 insertions, 1 deletions

diff --git a/fs/9p/fid.h b/fs/9p/fid.h
index 8a4e8cd12ca2..11576e1364bf 100644
--- a/fs/9p/fid.h
+++ b/fs/9p/fid.h
@@ -7,14 +7,16 @@
 #ifndef FS_9P_FID_H
 #define FS_9P_FID_H
 #include <linux/list.h>
+#include "v9fs.h"
 
+struct p9_fid *v9fs_fid_find_inode(struct inode *inode, bool want_writeable,
+	kuid_t uid, bool any);
 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry);
 static inline struct p9_fid *v9fs_parent_fid(struct dentry *dentry)
 {
 	return v9fs_fid_lookup(dentry->d_parent);
 }
 void v9fs_fid_add(struct dentry *dentry, struct p9_fid **fid);
-struct p9_fid *v9fs_writeback_fid(struct dentry *dentry);
 void v9fs_open_fid_add(struct inode *inode, struct p9_fid **fid);
 static inline struct p9_fid *clone_fid(struct p9_fid *fid)
 {
@@ -32,4 +34,33 @@ static inline struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
 	p9_fid_put(fid);
 	return nfid;
 }
+/**
+ * v9fs_fid_addmodes - add cache flags to fid mode (for client use only)
+ * @fid: fid to augment
+ * @s_flags: session info mount flags
+ * @s_cache: session info cache flags
+ * @f_flags: unix open flags
+ *
+ * make sure mode reflects flags of underlying mounts
+ * also qid.version == 0 reflects a synthetic or legacy file system
+ * NOTE: these are set after open so only reflect 9p client not
+ * underlying file system on server.
+ */
+static inline void v9fs_fid_add_modes(struct p9_fid *fid, int s_flags,
+	int s_cache, unsigned int f_flags)
+{
+	if (fid->qid.type != P9_QTFILE)
+		return;
+
+	if ((!s_cache) ||
+	   ((fid->qid.version == 0) && !(s_flags & V9FS_IGNORE_QV)) ||
+	   (s_flags & V9FS_DIRECT_IO) || (f_flags & O_DIRECT)) {
+		fid->mode |= P9L_DIRECT; /* no read or write cache */
+	} else if ((s_cache < CACHE_WRITEBACK) ||
+				(f_flags & O_DSYNC) | (s_flags & V9FS_SYNC)) {
+		fid->mode |= P9L_NOWRITECACHE;
+	} else if (s_cache == CACHE_LOOSE) {
+		fid->mode |= P9L_LOOSE; /* noncoherent cache */
+	}
+}
 #endif