diff options
| -rw-r--r-- | fs/exportfs/expfs.c | 164 |
1 files changed, 86 insertions, 78 deletions
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c index d8ba88a..d32ead9 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -126,6 +126,86 @@ static void clear_disconnected(struct dentry *dentry) } /* + * Reconnect a directory dentry with its parent. + * + * This can return a dentry, or NULL, or an error. + * + * In the first case the returned dentry is the parent of the given + * dentry, and may itself need to be reconnected to its parent. + * + * In the NULL case, a concurrent VFS operation has either renamed or + * removed this directory. The concurrent operation has reconnected our + * dentry, so we no longer need to. + */ +static struct dentry *reconnect_one(struct vfsmount *mnt, + struct dentry *dentry, char *nbuf) +{ + struct dentry *parent; + struct dentry *tmp; + int err; + + parent = ERR_PTR(-EACCES); + mutex_lock(&dentry->d_inode->i_mutex); + if (mnt->mnt_sb->s_export_op->get_parent) + parent = mnt->mnt_sb->s_export_op->get_parent(dentry); + mutex_unlock(&dentry->d_inode->i_mutex); + + if (IS_ERR(parent)) { + dprintk("%s: get_parent of %ld failed, err %d\n", + __func__, dentry->d_inode->i_ino, PTR_ERR(parent)); + return parent; + } + + dprintk("%s: find name of %lu in %lu\n", __func__, + dentry->d_inode->i_ino, parent->d_inode->i_ino); + err = exportfs_get_name(mnt, parent, nbuf, dentry); + if (err == -ENOENT) + goto out_reconnected; + if (err) + goto out_err; + dprintk("%s: found name: %s\n", __func__, nbuf); + mutex_lock(&parent->d_inode->i_mutex); + tmp = lookup_one_len(nbuf, parent, strlen(nbuf)); + mutex_unlock(&parent->d_inode->i_mutex); + if (IS_ERR(tmp)) { + dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp)); + goto out_err; + } + if (tmp != dentry) { + dput(tmp); + goto out_reconnected; + } + dput(tmp); + if (IS_ROOT(dentry)) { + err = -ESTALE; + goto out_err; + } + return parent; + +out_err: + dput(parent); + return ERR_PTR(err); +out_reconnected: + dput(parent); + /* + * Someone must have renamed our entry into another parent, in + * which case it has been reconnected by the rename. + * + * Or someone removed it entirely, in which case filehandle + * lookup will succeed but the directory is now IS_DEAD and + * subsequent operations on it will fail. + * + * Alternatively, maybe there was no race at all, and the + * filesystem is just corrupt and gave us a parent that doesn't + * actually contain any entry pointing to this inode. So, + * double check that this worked and return -ESTALE if not: + */ + if (!dentry_connected(dentry)) + return ERR_PTR(-ESTALE); + return NULL; +} + +/* * Make sure target_dir is fully connected to the dentry tree. * * On successful return, DCACHE_DISCONNECTED will be cleared on @@ -158,76 +238,19 @@ reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf) dput(pd); break; } else { + struct dentry *parent; /* * We have hit the top of a disconnected path, try to * find parent and connect. - * - * Racing with some other process renaming a directory - * isn't much of a problem here. If someone renames - * the directory, it will end up properly connected, - * which is what we want - * - * Getting the parent can't be supported generically, - * the locking is too icky. - * - * Instead we just return EACCES. If server reboots - * or inodes get flushed, you lose - */ - struct dentry *ppd = ERR_PTR(-EACCES); - struct dentry *npd; - - mutex_lock(&pd->d_inode->i_mutex); - if (mnt->mnt_sb->s_export_op->get_parent) - ppd = mnt->mnt_sb->s_export_op->get_parent(pd); - mutex_unlock(&pd->d_inode->i_mutex); - - if (IS_ERR(ppd)) { - err = PTR_ERR(ppd); - dprintk("%s: get_parent of %ld failed, err %d\n", - __func__, pd->d_inode->i_ino, err); - dput(pd); - break; - } - - dprintk("%s: find name of %lu in %lu\n", __func__, - pd->d_inode->i_ino, ppd->d_inode->i_ino); - err = exportfs_get_name(mnt, ppd, nbuf, pd); - if (err) { - dput(ppd); - dput(pd); - if (err == -ENOENT) - /* some race between get_parent and - * get_name? - */ - goto out_reconnected; - break; - } - dprintk("%s: found name: %s\n", __func__, nbuf); - mutex_lock(&ppd->d_inode->i_mutex); - npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); - mutex_unlock(&ppd->d_inode->i_mutex); - if (IS_ERR(npd)) { - err = PTR_ERR(npd); - dprintk("%s: lookup failed: %d\n", - __func__, err); - dput(ppd); - dput(pd); - break; - } - /* we didn't really want npd, we really wanted - * a side-effect of the lookup. - * hopefully, npd == pd, though it isn't really - * a problem if it isn't */ - dput(npd); - dput(ppd); - if (npd != pd) + parent = reconnect_one(mnt, pd, nbuf); + if (!parent) goto out_reconnected; - if (IS_ROOT(pd)) { - /* something went wrong, we have to give up */ - dput(pd); + if (IS_ERR(parent)) { + err = PTR_ERR(parent); break; } + dput(parent); } dput(pd); } @@ -241,21 +264,6 @@ reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf) return 0; out_reconnected: - /* - * Someone must have renamed our entry into another parent, in - * which case it has been reconnected by the rename. - * - * Or someone removed it entirely, in which case filehandle - * lookup will succeed but the directory is now IS_DEAD and - * subsequent operations on it will fail. - * - * Alternatively, maybe there was no race at all, and the - * filesystem is just corrupt and gave us a parent that doesn't - * actually contain any entry pointing to this inode. So, - * double check that this worked and return -ESTALE if not: - */ - if (!dentry_connected(target_dir)) - return -ESTALE; clear_disconnected(target_dir); return 0; } |
