[PATCH] FUSE: atomic create+open

This patch adds an atomic create+open operation.  This does not yet work if
the file type changes between lookup and create+open, but solves the
permission checking problems for the separte create and open methods.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 105 insertions, 1 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 4bc1afcc476d..83be119ef067 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -13,6 +13,7 @@
 #include <linux/gfp.h>
 #include <linux/sched.h>
 #include <linux/namei.h>
+#include <linux/mount.h>
 
 static inline unsigned long time_to_jiffies(unsigned long sec,
                                             unsigned long nsec)
@@ -134,6 +135,101 @@ static void fuse_invalidate_entry(struct dentry *entry)
         entry->d_time = jiffies - 1;
 }
 
+static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
+                            struct nameidata *nd)
+{
+        int err;
+        struct inode *inode;
+        struct fuse_conn *fc = get_fuse_conn(dir);
+        struct fuse_req *req;
+        struct fuse_open_in inarg;
+        struct fuse_open_out outopen;
+        struct fuse_entry_out outentry;
+        struct fuse_inode *fi;
+        struct fuse_file *ff;
+        struct file *file;
+        int flags = nd->intent.open.flags - 1;
+
+        err = -ENOSYS;
+        if (fc->no_create)
+                goto out;
+
+        err = -ENAMETOOLONG;
+        if (entry->d_name.len > FUSE_NAME_MAX)
+                goto out;
+
+        err = -EINTR;
+        req = fuse_get_request(fc);
+        if (!req)
+                goto out;
+
+        ff = fuse_file_alloc();
+        if (!ff)
+                goto out_put_request;
+
+        flags &= ~O_NOCTTY;
+        memset(&inarg, 0, sizeof(inarg));
+        inarg.flags = flags;
+        inarg.mode = mode;
+        req->in.h.opcode = FUSE_CREATE;
+        req->in.h.nodeid = get_node_id(dir);
+        req->inode = dir;
+        req->in.numargs = 2;
+        req->in.args[0].size = sizeof(inarg);
+        req->in.args[0].value = &inarg;
+        req->in.args[1].size = entry->d_name.len + 1;
+        req->in.args[1].value = entry->d_name.name;
+        req->out.numargs = 2;
+        req->out.args[0].size = sizeof(outentry);
+        req->out.args[0].value = &outentry;
+        req->out.args[1].size = sizeof(outopen);
+        req->out.args[1].value = &outopen;
+        request_send(fc, req);
+        err = req->out.h.error;
+        if (err) {
+                if (err == -ENOSYS)
+                        fc->no_create = 1;
+                goto out_free_ff;
+        }
+
+        err = -EIO;
+        if (!S_ISREG(outentry.attr.mode))
+                goto out_free_ff;
+
+        inode = fuse_iget(dir->i_sb, outentry.nodeid, outentry.generation,
+                          &outentry.attr);
+        err = -ENOMEM;
+        if (!inode) {
+                flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
+                ff->fh = outopen.fh;
+                fuse_send_release(fc, ff, outentry.nodeid, NULL, flags, 0);
+                goto out_put_request;
+        }
+        fuse_put_request(fc, req);
+        entry->d_time = time_to_jiffies(outentry.entry_valid,
+                                        outentry.entry_valid_nsec);
+        fi = get_fuse_inode(inode);
+        fi->i_time = time_to_jiffies(outentry.attr_valid,
+                                     outentry.attr_valid_nsec);
+
+        d_instantiate(entry, inode);
+        file = lookup_instantiate_filp(nd, entry, generic_file_open);
+        if (IS_ERR(file)) {
+                ff->fh = outopen.fh;
+                fuse_send_release(fc, ff, outentry.nodeid, inode, flags, 0);
+                return PTR_ERR(file);
+        }
+        fuse_finish_open(inode, file, ff, &outopen);
+        return 0;
+
+ out_free_ff:
+        fuse_file_free(ff);
+ out_put_request:
+        fuse_put_request(fc, req);
+ out:
+        return err;
+}
+
 static int create_new_entry(struct fuse_conn *fc, struct fuse_req *req,
                             struct inode *dir, struct dentry *entry,
                             int mode)
@@ -208,6 +304,12 @@ static int fuse_mknod(struct inode *dir, struct dentry *entry, int mode,
 static int fuse_create(struct inode *dir, struct dentry *entry, int mode,
                        struct nameidata *nd)
 {
+        if (nd && (nd->flags & LOOKUP_CREATE)) {
+                int err = fuse_create_open(dir, entry, mode, nd);
+                if (err != -ENOSYS)
+                        return err;
+                /* Fall back on mknod */
+        }
         return fuse_mknod(dir, entry, mode, 0);
 }
 
@@ -767,7 +869,9 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
                                   struct nameidata *nd)
 {
         struct inode *inode;
-        int err = fuse_lookup_iget(dir, entry, &inode);
+        int err;
+
+        err = fuse_lookup_iget(dir, entry, &inode);
         if (err)
                 return ERR_PTR(err);
         if (inode && S_ISDIR(inode->i_mode)) {