ceph: simplify+fix atomic_open

The initial ->atomic_open op was carried over from the old intent code,
which was incomplete and didn't really work.  Replace it with a fresh
method.  In particular:

 * always attempt to do an atomic open+lookup, both for the create case
   and for lookups of existing files.
 * fix symlink handling by returning 1 to the VFS so that we can follow
   the link to its destination. This fixes a longstanding ceph bug (#2392).

Signed-off-by: Sage Weil <sage@inktank.com>

3 files changed, 40 insertions, 66 deletions

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index f391f1e7541..e5b77319c97 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -633,44 +633,6 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
         return dentry;
 }
 
-int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
-                     struct file *file, unsigned flags, umode_t mode,
-                     int *opened)
-{
-        int err;
-        struct dentry *res = NULL;
-
-        if (!(flags & O_CREAT)) {
-                if (dentry->d_name.len > NAME_MAX)
-                        return -ENAMETOOLONG;
-
-                err = ceph_init_dentry(dentry);
-                if (err < 0)
-                        return err;
-
-                return ceph_lookup_open(dir, dentry, file, flags, mode, opened);
-        }
-
-        if (d_unhashed(dentry)) {
-                res = ceph_lookup(dir, dentry, 0);
-                if (IS_ERR(res))
-                        return PTR_ERR(res);
-
-                if (res)
-                        dentry = res;
-        }
-
-        /* We don't deal with positive dentries here */
-        if (dentry->d_inode)
-                return finish_no_open(file, res);
-
-        *opened |= FILE_CREATED;
-        err = ceph_lookup_open(dir, dentry, file, flags, mode, opened);
-        dput(res);
-
-        return err;
-}
-
 /*
  * If we do a create but get no trace back from the MDS, follow up with
  * a lookup (the VFS expects us to link up the provided dentry).
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 1b81d6c3187..ecebbc09bfc 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -4,6 +4,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/file.h>
+#include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/writeback.h>
 
@@ -106,9 +107,6 @@ static int ceph_init_file(struct inode *inode, struct file *file, int fmode)
 }
 
 /*
- * If the filp already has private_data, that means the file was
- * already opened by intent during lookup, and we do nothing.
- *
  * If we already have the requisite capabilities, we can satisfy
  * the open request locally (no need to request new caps from the
  * MDS).  We do, however, need to inform the MDS (asynchronously)
@@ -207,24 +205,29 @@ out:
 
 
 /*
- * Do a lookup + open with a single request.
- *
- * If this succeeds, but some subsequent check in the vfs
- * may_open() fails, the struct *file gets cleaned up (i.e.
- * ceph_release gets called).  So fear not!
+ * Do a lookup + open with a single request.  If we get a non-existent
+ * file or symlink, return 1 so the VFS can retry.
  */
-int ceph_lookup_open(struct inode *dir, struct dentry *dentry,
+int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
                      struct file *file, unsigned flags, umode_t mode,
                      int *opened)
 {
         struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
         struct ceph_mds_client *mdsc = fsc->mdsc;
         struct ceph_mds_request *req;
-        struct dentry *ret;
+        struct dentry *dn;
         int err;
 
-        dout("ceph_lookup_open dentry %p '%.*s' flags %d mode 0%o\n",
-             dentry, dentry->d_name.len, dentry->d_name.name, flags, mode);
+        dout("atomic_open %p dentry %p '%.*s' %s flags %d mode 0%o\n",
+             dir, dentry, dentry->d_name.len, dentry->d_name.name,
+             d_unhashed(dentry) ? "unhashed" : "hashed", flags, mode);
+
+        if (dentry->d_name.len > NAME_MAX)
+                return -ENAMETOOLONG;
+
+        err = ceph_init_dentry(dentry);
+        if (err < 0)
+                return err;
 
         /* do the open */
         req = prepare_open_request(dir->i_sb, flags, mode);
@@ -241,22 +244,31 @@ int ceph_lookup_open(struct inode *dir, struct dentry *dentry,
                                    (flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
                                    req);
         err = ceph_handle_snapdir(req, dentry, err);
-        if (err)
-                goto out;
-        if ((flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
+        if (err == 0 && (flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
                 err = ceph_handle_notrace_create(dir, dentry);
-        if (err)
-                goto out;
-        err = finish_open(file, req->r_dentry, ceph_open, opened);
-out:
-        ret = ceph_finish_lookup(req, dentry, err);
-        ceph_mdsc_put_request(req);
-        dout("ceph_lookup_open result=%p\n", ret);
 
-        if (IS_ERR(ret))
-                return PTR_ERR(ret);
+        if (d_unhashed(dentry)) {
+                dn = ceph_finish_lookup(req, dentry, err);
+                if (IS_ERR(dn))
+                        err = PTR_ERR(dn);
+        } else {
+                /* we were given a hashed negative dentry */
+                dn = NULL;
+        }
+        if (err)
+                goto out_err;
+        if (dn || dentry->d_inode == NULL || S_ISLNK(dentry->d_inode->i_mode)) {
+                /* make vfs retry on splice, ENOENT, or symlink */
+                dout("atomic_open finish_no_open on dn %p\n", dn);
+                err = finish_no_open(file, dn);
+        } else {
+                dout("atomic_open finish_open on dn %p\n", dn);
+                err = finish_open(file, dentry, ceph_open, opened);
+        }
 
-        dput(ret);
+out_err:
+        ceph_mdsc_put_request(req);
+        dout("atomic_open result=%d\n", err);
         return err;
 }
 
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index ebc95cc652b..66ebe720e40 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -806,9 +806,9 @@ extern int ceph_copy_from_page_vector(struct page **pages,
                                     loff_t off, size_t len);
 extern struct page **ceph_alloc_page_vector(int num_pages, gfp_t flags);
 extern int ceph_open(struct inode *inode, struct file *file);
-extern int ceph_lookup_open(struct inode *dir, struct dentry *dentry,
-                             struct file *od, unsigned flags,
-                             umode_t mode, int *opened);
+extern int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
+                            struct file *file, unsigned flags, umode_t mode,
+                            int *opened);
 extern int ceph_release(struct inode *inode, struct file *filp);
 
 /* dir.c */