fuse: add list of writable files to fuse_inode

Each WRITE request must carry a valid file descriptor.  When a page is written
back from a memory mapping, the file through which the page was dirtied is not
available, so a new mechananism is needed to find a suitable file in
->writepage(s).

A list of fuse_files is added to fuse_inode.  The file is removed from the
list in fuse_release().

This patch is in preparation for writable mmap support.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 15 insertions, 0 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 471ea70be48d..c4c59c7d0038 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -56,6 +56,7 @@ struct fuse_file *fuse_file_alloc(void)
                         kfree(ff);
                         ff = NULL;
                 }
+                INIT_LIST_HEAD(&ff->write_entry);
                 atomic_set(&ff->count, 0);
         }
         return ff;
@@ -150,12 +151,18 @@ int fuse_release_common(struct inode *inode, struct file *file, int isdir)
 {
         struct fuse_file *ff = file->private_data;
         if (ff) {
+                struct fuse_conn *fc = get_fuse_conn(inode);
+
                 fuse_release_fill(ff, get_node_id(inode), file->f_flags,
                                   isdir ? FUSE_RELEASEDIR : FUSE_RELEASE);
 
                 /* Hold vfsmount and dentry until release is finished */
                 ff->reserved_req->vfsmount = mntget(file->f_path.mnt);
                 ff->reserved_req->dentry = dget(file->f_path.dentry);
+
+                spin_lock(&fc->lock);
+                list_del(&ff->write_entry);
+                spin_unlock(&fc->lock);
                 /*
                  * Normally this will send the RELEASE request,
                  * however if some asynchronous READ or WRITE requests
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index b24fc9b386f8..5657cca0d0cb 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -70,6 +70,9 @@ struct fuse_inode {
 
         /** Version of last attribute change */
         u64 attr_version;
+
+        /** Files usable in writepage.  Protected by fc->lock */
+        struct list_head write_files;
 };
 
 /** FUSE specific file data */
@@ -82,6 +85,9 @@ struct fuse_file {
 
         /** Refcount */
         atomic_t count;
+
+        /** Entry on inode's write_files list */
+        struct list_head write_entry;
 };
 
 /** One input argument of a request */
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 3c13981f48e2..49d716036ea7 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -56,6 +56,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
         fi->i_time = 0;
         fi->nodeid = 0;
         fi->nlookup = 0;
+        INIT_LIST_HEAD(&fi->write_files);
         fi->forget_req = fuse_request_alloc();
         if (!fi->forget_req) {
                 kmem_cache_free(fuse_inode_cachep, inode);
@@ -68,6 +69,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
 static void fuse_destroy_inode(struct inode *inode)
 {
         struct fuse_inode *fi = get_fuse_inode(inode);
+        BUG_ON(!list_empty(&fi->write_files));
         if (fi->forget_req)
                 fuse_request_free(fi->forget_req);
         kmem_cache_free(fuse_inode_cachep, inode);