FUSE: Adapt readdirplus to application usage patterns

Use the same adaptive readdirplus mechanism as NFS:

http://permalink.gmane.org/gmane.linux.nfs/49299

If the user space implementation wants to disable readdirplus
temporarily, it could just return ENOTSUPP. Then kernel will
recall it with readdir.

Signed-off-by: Feng Shuo <steve.shuo.feng@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

3 files changed, 38 insertions, 3 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index aa0b6ade0e68..dc5e64893375 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -14,6 +14,27 @@
 #include <linux/namei.h>
 #include <linux/slab.h>
 
+static bool fuse_use_readdirplus(struct inode *dir, struct file *filp)
+{
+        struct fuse_conn *fc = get_fuse_conn(dir);
+        struct fuse_inode *fi = get_fuse_inode(dir);
+
+        if (!fc->do_readdirplus)
+                return false;
+        if (test_and_clear_bit(FUSE_I_ADVISE_RDPLUS, &fi->state))
+                return true;
+        if (filp->f_pos == 0)
+                return true;
+        return false;
+}
+
+static void fuse_advise_use_readdirplus(struct inode *dir)
+{
+        struct fuse_inode *fi = get_fuse_inode(dir);
+
+        set_bit(FUSE_I_ADVISE_RDPLUS, &fi->state);
+}
+
 #if BITS_PER_LONG >= 64
 static inline void fuse_dentry_settime(struct dentry *entry, u64 time)
 {
@@ -219,6 +240,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
                                        attr_version);
                 fuse_change_entry_timeout(entry, &outarg);
         }
+        fuse_advise_use_readdirplus(inode);
         return 1;
 }
 
@@ -355,6 +377,7 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
         else
                 fuse_invalidate_entry_cache(entry);
 
+        fuse_advise_use_readdirplus(dir);
         return newent;
 
  out_iput:
@@ -1290,7 +1313,7 @@ static int parse_dirplusfile(char *buf, size_t nbytes, struct file *file,
 
 static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
 {
-        int err;
+        int plus, err;
         size_t nbytes;
         struct page *page;
         struct inode *inode = file->f_path.dentry->d_inode;
@@ -1310,11 +1333,13 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
                 fuse_put_request(fc, req);
                 return -ENOMEM;
         }
+
+        plus = fuse_use_readdirplus(inode, file);
         req->out.argpages = 1;
         req->num_pages = 1;
         req->pages[0] = page;
         req->page_descs[0].length = PAGE_SIZE;
-        if (fc->do_readdirplus) {
+        if (plus) {
                 attr_version = fuse_get_attr_version(fc);
                 fuse_read_fill(req, file, file->f_pos, PAGE_SIZE,
                                FUSE_READDIRPLUS);
@@ -1327,7 +1352,7 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
         err = req->out.h.error;
         fuse_put_request(fc, req);
         if (!err) {
-                if (fc->do_readdirplus) {
+                if (plus) {
                         err = parse_dirplusfile(page_address(page), nbytes,
                                                 file, dstbuf, filldir,
                                                 attr_version);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index af51c146a9ae..fc55dd33c1e2 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -106,6 +106,15 @@ struct fuse_inode {
 
         /** List of writepage requestst (pending or sent) */
         struct list_head writepages;
+
+        /** Miscellaneous bits describing inode state */
+        unsigned long state;
+};
+
+/** FUSE inode state bits */
+enum {
+        /** Advise readdirplus  */
+        FUSE_I_ADVISE_RDPLUS,
 };
 
 struct fuse_conn;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 79b70deb7cd6..9876a87255fe 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -92,6 +92,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
         fi->attr_version = 0;
         fi->writectr = 0;
         fi->orig_ino = 0;
+        fi->state = 0;
         INIT_LIST_HEAD(&fi->write_files);
         INIT_LIST_HEAD(&fi->queued_writes);
         INIT_LIST_HEAD(&fi->writepages);