fuse: Trust kernel i_mtime only

Let the kernel maintain i_mtime locally:
 - clear S_NOCMTIME
 - implement i_op->update_time()
 - flush mtime on fsync and last close
 - update i_mtime explicitly on truncate and fallocate

Fuse inode flag FUSE_I_MTIME_DIRTY serves as indication that local i_mtime
should be flushed to the server eventually.

Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index c668c8436894..1061b0d9b86d 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -170,8 +170,11 @@ void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
         inode->i_blocks  = attr->blocks;
         inode->i_atime.tv_sec   = attr->atime;
         inode->i_atime.tv_nsec  = attr->atimensec;
-        inode->i_mtime.tv_sec   = attr->mtime;
-        inode->i_mtime.tv_nsec  = attr->mtimensec;
+        /* mtime from server may be stale due to local buffered write */
+        if (!fc->writeback_cache || !S_ISREG(inode->i_mode)) {
+                inode->i_mtime.tv_sec   = attr->mtime;
+                inode->i_mtime.tv_nsec  = attr->mtimensec;
+        }
         inode->i_ctime.tv_sec   = attr->ctime;
         inode->i_ctime.tv_nsec  = attr->ctimensec;
 
@@ -250,6 +253,8 @@ static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
 {
         inode->i_mode = attr->mode & S_IFMT;
         inode->i_size = attr->size;
+        inode->i_mtime.tv_sec  = attr->mtime;
+        inode->i_mtime.tv_nsec = attr->mtimensec;
         if (S_ISREG(inode->i_mode)) {
                 fuse_init_common(inode);
                 fuse_init_file_inode(inode);
@@ -296,7 +301,9 @@ struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
                 return NULL;
 
         if ((inode->i_state & I_NEW)) {
-                inode->i_flags |= S_NOATIME|S_NOCMTIME;
+                inode->i_flags |= S_NOATIME;
+                if (!fc->writeback_cache || !S_ISREG(inode->i_mode))
+                        inode->i_flags |= S_NOCMTIME;
                 inode->i_generation = generation;
                 inode->i_data.backing_dev_info = &fc->bdi;
                 fuse_init_inode(inode, attr);