ceph: use __getname/__putname in ceph_mdsc_build_path

Al suggested we get rid of the kmalloc here and just use __getname
and __putname to get a full PATH_MAX pathname buffer.

Since we build the path in reverse, we continue to return a pointer
to the beginning of the string and the length, and add a new helper
to free the thing at the end.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c
index 777f6ce..b014fc7 100644 (file)
--- a/fs/ceph/debugfs.c
+++ b/fs/ceph/debugfs.c
@@ -88,7 +88,7 @@ static int mdsc_show(struct seq_file *s, void *p)
                                   req->r_dentry,
                                   path ? path : "");
                        spin_unlock(&req->r_dentry->d_lock);
-                       kfree(path);
+                       ceph_mdsc_free_path(path, pathlen);
                } else if (req->r_path1) {
                        seq_printf(s, " #%llx/%s", req->r_ino1.ino,
                                   req->r_path1);
@@ -108,7 +108,7 @@ static int mdsc_show(struct seq_file *s, void *p)
                                   req->r_old_dentry,
                                   path ? path : "");
                        spin_unlock(&req->r_old_dentry->d_lock);
-                       kfree(path);
+                       ceph_mdsc_free_path(path, pathlen);
                } else if (req->r_path2 && req->r_op != CEPH_MDS_OP_SYMLINK) {
                        if (req->r_ino2.ino)
                                seq_printf(s, " #%llx/%s", req->r_ino2.ino,

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 7af7228..d29f6c0 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2094,39 +2094,24 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
 {
        struct dentry *temp;
        char *path;
-       int len, pos;
+       int pos;
        unsigned seq;
        u64 base;
 
        if (!dentry)
                return ERR_PTR(-EINVAL);
 
-retry:
-       len = 0;
-       seq = read_seqbegin(&rename_lock);
-       rcu_read_lock();
-       for (temp = dentry; !IS_ROOT(temp);) {
-               struct inode *inode = d_inode(temp);
-               if (inode && ceph_snap(inode) == CEPH_SNAPDIR)
-                       len++;  /* slash only */
-               else if (stop_on_nosnap && inode &&
-                        ceph_snap(inode) == CEPH_NOSNAP)
-                       break;
-               else
-                       len += 1 + temp->d_name.len;
-               temp = temp->d_parent;
-       }
-       rcu_read_unlock();
-       if (len)
-               len--;  /* no leading '/' */
-
-       path = kmalloc(len+1, GFP_NOFS);
+       path = __getname();
        if (!path)
                return ERR_PTR(-ENOMEM);
-       pos = len;
-       path[pos] = 0;  /* trailing null */
+retry:
+       pos = PATH_MAX - 1;
+       path[pos] = '\0';
+
+       seq = read_seqbegin(&rename_lock);
        rcu_read_lock();
-       for (temp = dentry; !IS_ROOT(temp) && pos != 0; ) {
+       temp = dentry;
+       for (;;) {
                struct inode *inode;
 
                spin_lock(&temp->d_lock);
@@ -2144,32 +2129,38 @@ retry:
                                spin_unlock(&temp->d_lock);
                                break;
                        }
-                       strncpy(path + pos, temp->d_name.name,
-                               temp->d_name.len);
+                       memcpy(path + pos, temp->d_name.name, temp->d_name.len);
                }
                spin_unlock(&temp->d_lock);
-               if (pos)
-                       path[--pos] = '/';
                temp = temp->d_parent;
+
+               /* Are we at the root? */
+               if (IS_ROOT(temp))
+                       break;
+
+               /* Are we out of buffer? */
+               if (--pos < 0)
+                       break;
+
+               path[pos] = '/';
        }
        base = ceph_ino(d_inode(temp));
        rcu_read_unlock();
-       if (pos != 0 || read_seqretry(&rename_lock, seq)) {
+       if (pos < 0 || read_seqretry(&rename_lock, seq)) {
                pr_err("build_path did not end path lookup where "
-                      "expected, namelen is %d, pos is %d\n", len, pos);
+                      "expected, pos is %d\n", pos);
                /* presumably this is only possible if racing with a
                   rename of one of the parent directories (we can not
                   lock the dentries above us to prevent this, but
                   retrying should be harmless) */
-               kfree(path);
                goto retry;
        }
 
        *pbase = base;
-       *plen = len;
+       *plen = PATH_MAX - 1 - pos;
        dout("build_path on %p %d built %llx '%.*s'\n",
-            dentry, d_count(dentry), base, len, path);
-       return path;
+            dentry, d_count(dentry), base, *plen, path + pos);
+       return path + pos;
 }
 
 static int build_dentry_path(struct dentry *dentry, struct inode *dir,
@@ -2376,10 +2367,10 @@ static struct ceph_msg *create_request_message(struct ceph_mds_client *mdsc,
 
 out_free2:
        if (freepath2)
-               kfree((char *)path2);
+               ceph_mdsc_free_path((char *)path2, pathlen2);
 out_free1:
        if (freepath1)
-               kfree((char *)path1);
+               ceph_mdsc_free_path((char *)path1, pathlen1);
 out:
        return msg;
 }
@@ -3451,7 +3442,7 @@ out_freeflocks:
                ceph_pagelist_encode_string(pagelist, path, pathlen);
                ceph_pagelist_append(pagelist, &rec, sizeof(rec.v1));
 out_freepath:
-               kfree(path);
+               ceph_mdsc_free_path(path, pathlen);
        }
 
 out_err:

diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index 0d1f673..ebcad5a 100644 (file)
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -492,6 +492,12 @@ extern int ceph_iterate_session_caps(struct ceph_mds_session *session,
                                     void *arg);
 extern void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc);
 
+static inline void ceph_mdsc_free_path(char *path, int len)
+{
+       if (path)
+               __putname(path - (PATH_MAX - 1 - len));
+}
+
 extern char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
                                  int stop_on_nosnap);