fs/9p: Add fid to inode in cached mode

The fid attached to inode will be opened O_RDWR mode and is used
for dirty page writeback only.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

5 files changed, 83 insertions, 3 deletions

diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index b00223c99d70..9d6a5d3bfe15 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -261,3 +261,29 @@ struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
         ret = p9_client_walk(fid, 0, NULL, 1);
         return ret;
 }
+
+
+struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
+{
+        int err;
+        struct p9_fid *fid;
+
+        fid = v9fs_fid_clone(dentry);
+        if (IS_ERR(fid))
+                goto error_out;
+        /*
+         * writeback fid will only be used to write back the
+         * dirty pages. We always request for the open fid in read-write
+         * mode so that a partial page write which result in page
+         * read can work.
+         * FIXME!!: we should make the fid owned by uid = 0
+         */
+        err = p9_client_open(fid, O_RDWR);
+        if (err < 0) {
+                p9_client_clunk(fid);
+                fid = ERR_PTR(err);
+                goto error_out;
+        }
+error_out:
+        return fid;
+}
diff --git a/fs/9p/fid.h b/fs/9p/fid.h
index c3bbd6af996d..c058f1c7656e 100644
--- a/fs/9p/fid.h
+++ b/fs/9p/fid.h
@@ -45,3 +45,4 @@ struct v9fs_dentry {
 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry);
 struct p9_fid *v9fs_fid_clone(struct dentry *dentry);
 int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid);
+struct p9_fid *v9fs_writeback_fid(struct dentry *dentry);
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 6e1e8f43edac..e966f15f92ec 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -86,11 +86,30 @@ int v9fs_file_open(struct inode *inode, struct file *file)
         }
 
         file->private_data = fid;
+        if (v9ses->cache && !inode->i_private) {
+                /*
+                 * clone a fid and add it to inode->i_private
+                 * we do it during open time instead of
+                 * page dirty time via write_begin/page_mkwrite
+                 * because we want write after unlink usecase
+                 * to work.
+                 */
+                fid = v9fs_writeback_fid(file->f_path.dentry);
+                if (IS_ERR(fid)) {
+                        err = PTR_ERR(fid);
+                        goto out_error;
+                }
+                inode->i_private = (void *) fid;
+        }
 #ifdef CONFIG_9P_FSCACHE
         if (v9ses->cache)
                 v9fs_cache_inode_set_cookie(inode, file);
 #endif
         return 0;
+out_error:
+        p9_client_clunk(file->private_data);
+        file->private_data = NULL;
+        return err;
 }
 
 /**
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 95f55011aca1..a0d65a398729 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -417,6 +417,11 @@ void v9fs_evict_inode(struct inode *inode)
 #ifdef CONFIG_9P_FSCACHE
         v9fs_cache_inode_put_cookie(inode);
 #endif
+        /* clunk the fid stashed in inode->i_private */
+        if (inode->i_private) {
+                p9_client_clunk((struct p9_fid *)inode->i_private);
+                inode->i_private = NULL;
+        }
 }
 
 struct inode *
@@ -578,7 +583,7 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
         u32 perm;
         int flags;
         struct v9fs_session_info *v9ses;
-        struct p9_fid *fid;
+        struct p9_fid *fid, *inode_fid;
         struct file *filp;
 
         err = 0;
@@ -601,6 +606,21 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
 
         /* if we are opening a file, assign the open fid to the file */
         if (nd && nd->flags & LOOKUP_OPEN) {
+                if (v9ses->cache && !dentry->d_inode->i_private) {
+                        /*
+                         * clone a fid and add it to inode->i_private
+                         * we do it during open time instead of
+                         * page dirty time via write_begin/page_mkwrite
+                         * because we want write after unlink usecase
+                         * to work.
+                         */
+                        inode_fid = v9fs_writeback_fid(dentry);
+                        if (IS_ERR(inode_fid)) {
+                                err = PTR_ERR(inode_fid);
+                                goto error;
+                        }
+                        dentry->d_inode->i_private = (void *) inode_fid;
+                }
                 filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
                 if (IS_ERR(filp)) {
                         err = PTR_ERR(filp);
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 265f5834498a..1327464bb2bb 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -142,7 +142,7 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
         mode_t mode;
         struct v9fs_session_info *v9ses;
         struct p9_fid *fid = NULL;
-        struct p9_fid *dfid, *ofid;
+        struct p9_fid *dfid, *ofid, *inode_fid;
         struct file *filp;
         struct p9_qid qid;
         struct inode *inode;
@@ -218,7 +218,21 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
 
         /* Now set the ACL based on the default value */
         v9fs_set_create_acl(dentry, dacl, pacl);
-
+        if (v9ses->cache && !inode->i_private) {
+                /*
+                 * clone a fid and add it to inode->i_private
+                 * we do it during open time instead of
+                 * page dirty time via write_begin/page_mkwrite
+                 * because we want write after unlink usecase
+                 * to work.
+                 */
+                inode_fid = v9fs_writeback_fid(dentry);
+                if (IS_ERR(inode_fid)) {
+                        err = PTR_ERR(inode_fid);
+                        goto error;
+                }
+                inode->i_private = (void *) inode_fid;
+        }
         /* Since we are opening a file, assign the open fid to the file */
         filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
         if (IS_ERR(filp)) {