Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754958Ab0HHPzo (ORCPT ); Sun, 8 Aug 2010 11:55:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36838 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754756Ab0HHPzg (ORCPT ); Sun, 8 Aug 2010 11:55:36 -0400 From: Valerie Aurora To: Alexander Viro Cc: Miklos Szeredi , Jan Blunck , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Valerie Aurora , Valdis.Kletnieks@vt.edu Subject: [PATCH 28/39] union-mount: In-kernel file copyup routines Date: Sun, 8 Aug 2010 11:52:45 -0400 Message-Id: <1281282776-5447-29-git-send-email-vaurora@redhat.com> In-Reply-To: <1281282776-5447-1-git-send-email-vaurora@redhat.com> References: <1281282776-5447-1-git-send-email-vaurora@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10962 Lines: 402 When a file on the read-only layer of a union mount is altered, it must be copied up to the topmost read-write layer. This patch creates union_copyup() and its supporting routines. Thanks to Valdis Kletnieks for a bug fix. XXX - Miklos Szeredi points out: What happens if we crash halfway through the file copyup? Answer: A bug, the file is truncated. Needs fixing. Cc: Valdis.Kletnieks@vt.edu Signed-off-by: Valerie Aurora --- fs/union.c | 323 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ fs/union.h | 7 +- 2 files changed, 329 insertions(+), 1 deletions(-) diff --git a/fs/union.c b/fs/union.c index a91e8fc..103c436 100644 --- a/fs/union.c +++ b/fs/union.c @@ -24,6 +24,8 @@ #include #include #include +#include +#include #include "union.h" @@ -191,6 +193,72 @@ int needs_lookup_union(struct path *parent_path, struct path *path) return 1; } +/** + * union_copyup_xattr + * + * @old: dentry of original file + * @new: dentry of new copy + * + * Copy up extended attributes from the original file to the new one. + * + * XXX - Permissions? For now, copying up every xattr. + */ + +static int union_copyup_xattr(struct dentry *old, struct dentry *new) +{ + ssize_t list_size, size; + char *buf, *name, *value; + int error; + + /* Check for xattr support */ + if (!old->d_inode->i_op->getxattr || + !new->d_inode->i_op->getxattr) + return 0; + + /* Find out how big the list of xattrs is */ + list_size = vfs_listxattr(old, NULL, 0); + if (list_size <= 0) + return list_size; + + /* Allocate memory for the list */ + buf = kzalloc(list_size, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + /* Allocate memory for the xattr's value */ + error = -ENOMEM; + value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL); + if (!value) + goto out; + + /* Actually get the list of xattrs */ + list_size = vfs_listxattr(old, buf, list_size); + if (list_size <= 0) { + error = list_size; + goto out_free_value; + } + + for (name = buf; name < (buf + list_size); name += strlen(name) + 1) { + /* XXX Locking? old is on read-only fs */ + size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX); + if (size <= 0) { + error = size; + goto out_free_value; + } + /* XXX do we really need to check for size overflow? */ + /* XXX locks new dentry, lock ordering problems? */ + error = vfs_setxattr(new, name, value, size, 0); + if (error) + goto out_free_value; + } + +out_free_value: + kfree(value); +out: + kfree(buf); + return error; +} + /* * union_create_topmost_dir - Create a matching dir in the topmost file system */ @@ -209,6 +277,13 @@ int union_create_topmost_dir(struct path *parent, struct qstr *name, res = vfs_mkdir(parent->dentry->d_inode, topmost->dentry, mode); + if (res) + goto out; + + res = union_copyup_xattr(lower->dentry, topmost->dentry); + if (res) + dput(topmost->dentry); +out: mnt_drop_write(parent->mnt); return res; @@ -427,3 +502,251 @@ generic_readdir_fallthru(struct dentry *topmost_dentry, const char *name, } return -ENOENT; } + +/** + * union_create_file + * + * @nd: namediata for source file + * @old: path of the source file + * @new: path of the new file, negative dentry + * + * Must already have mnt_want_write() on the mnt and the parent's + * i_mutex. + */ + +static int union_create_file(struct nameidata *nd, struct path *old, + struct dentry *new) +{ + struct path *parent = &nd->path; + BUG_ON(!mutex_is_locked(&parent->dentry->d_inode->i_mutex)); + + return vfs_create(parent->dentry->d_inode, new, + old->dentry->d_inode->i_mode, nd); +} + +/** + * union_create_symlink + * + * @nd: namediata for source symlink + * @old: path of the source symlink + * @new: path of the new symlink, negative dentry + * + * Must already have mnt_want_write() on the mnt and the parent's + * i_mutex. + */ + +static int union_create_symlink(struct nameidata *nd, struct path *old, + struct dentry *new) +{ + void *cookie; + int error; + + BUG_ON(!mutex_is_locked(&nd->path.dentry->d_inode->i_mutex)); + /* + * We want the contents of this symlink, not to follow it, so + * this is modeled on generic_readlink() rather than + * do_follow_link(). + */ + nd->depth = 0; + cookie = old->dentry->d_inode->i_op->follow_link(old->dentry, nd); + if (IS_ERR(cookie)) + return PTR_ERR(cookie); + /* Create a copy of the link on the top layer */ + error = vfs_symlink(nd->path.dentry->d_inode, new, + nd_get_link(nd)); + if (old->dentry->d_inode->i_op->put_link) + old->dentry->d_inode->i_op->put_link(old->dentry, nd, cookie); + return error; +} + +/** + * union_copyup_data - Copy up len bytes of old's data to new + * + * @old: path of source file + * @new_mnt: vfsmount of target file + * @new_dentry: dentry of target file + * @len: number of bytes to copy + */ + +static int union_copyup_data(struct path *old, struct vfsmount *new_mnt, + struct dentry *new_dentry, size_t len) +{ + struct file *old_file; + struct file *new_file; + const struct cred *cred = current_cred(); + loff_t offset = 0; + long bytes; + int error = 0; + + if (len == 0) + return 0; + + /* Get reference to balance later fput() */ + path_get(old); + old_file = dentry_open(old->dentry, old->mnt, O_RDONLY, cred); + if (IS_ERR(old_file)) + return PTR_ERR(old_file); + + mntget(new_mnt); + dget(new_dentry); + new_file = dentry_open(new_dentry, new_mnt, O_WRONLY, cred); + if (IS_ERR(new_file)) { + error = PTR_ERR(new_file); + goto out_fput; + } + + bytes = do_splice_direct(old_file, &offset, new_file, len, + SPLICE_F_MOVE); + if (bytes < 0) + error = bytes; + + fput(new_file); +out_fput: + fput(old_file); + return error; +} + +/** + * __union_copyup_len - Copy up a file and len bytes of data + * + * @nd: nameidata for topmost parent dir + * @path: path of file to be copied up + * @len: number of bytes of file data to copy up + * + * Parent's i_mutex must be held by caller. Newly copied up path is + * returned in @path and original is path_put(). + */ + +static int __union_copyup_len(struct nameidata *nd, struct path *path, + size_t len) +{ + struct path *parent = &nd->path; + struct dentry *dentry; + int error; + + BUG_ON(!mutex_is_locked(&parent->dentry->d_inode->i_mutex)); + + dentry = lookup_one_len(path->dentry->d_name.name, parent->dentry, + path->dentry->d_name.len); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + + if (dentry->d_inode) { + /* + * We raced with someone else and "lost." That's + * okay, they did all the work of copying up the file. + * Note that currently data copyup happens under the + * parent dir's i_mutex. If we move it outside that, + * we'll need some way of waiting for the data copyup + * to complete here. + */ + error = 0; + goto out_newpath; + } + if (S_ISREG(path->dentry->d_inode->i_mode)) { + /* Create file */ + error = union_create_file(nd, path, dentry); + if (error) + goto out_dput; + /* Copyup data */ + error = union_copyup_data(path, parent->mnt, dentry, len); + } else { + BUG_ON(!S_ISLNK(path->dentry->d_inode->i_mode)); + error = union_create_symlink(nd, path, dentry); + } + if (error) { + /* Most likely error: ENOSPC */ + vfs_unlink(parent->dentry->d_inode, dentry); + goto out_dput; + } + /* XXX Copyup xattrs and any other dangly bits */ + error = union_copyup_xattr(path->dentry, dentry); + if (error) + goto out_dput; +out_newpath: + /* path_put() of original must happen before we copy in new */ + path_put(path); + path->dentry = dentry; + path->mnt = mntget(parent->mnt); + return error; +out_dput: + /* Don't path_put(path), let caller unwind */ + dput(dentry); + return error; +} + +/** + * do_union_copyup_len - Copy up a file given its path (and its parent's) + * + * @nd: nameidata for topmost parent dir + * @path: path of file to be copied up + * @copy_all: if set, copy all of the file's data and ignore @len + * @len: if @copy_all is not set, number of bytes of file data to copy up + * + * Newly copied up path is returned in @path. + */ + +static int do_union_copyup_len(struct nameidata *nd, struct path *path, + int copy_all, size_t len) +{ + struct path *parent = &nd->path; + int error; + + if (!IS_DIR_UNIONED(parent->dentry)) + return 0; + if (parent->mnt == path->mnt) + return 0; + if (!S_ISREG(path->dentry->d_inode->i_mode) && + !S_ISLNK(path->dentry->d_inode->i_mode)) + return 0; + + BUG_ON(!S_ISDIR(parent->dentry->d_inode->i_mode)); + + mutex_lock(&parent->dentry->d_inode->i_mutex); + error = -ENOENT; + if (IS_DEADDIR(parent->dentry->d_inode)) + goto out_unlock; + + if (copy_all && S_ISREG(path->dentry->d_inode->i_mode)) { + error = -EFBIG; + len = i_size_read(path->dentry->d_inode); + /* Check for overflow of file size */ + if (((size_t)len != len) || ((ssize_t)len != len)) + goto out_unlock; + } + + error = __union_copyup_len(nd, path, len); + +out_unlock: + mutex_unlock(&parent->dentry->d_inode->i_mutex); + return error; +} + +/* + * Helper function to copy up all of a file + */ +int union_copyup(struct nameidata *nd, struct path *path) +{ + return do_union_copyup_len(nd, path, 1, 0); +} + +/* + * Unlocked helper function to copy up all of a file + */ +int __union_copyup(struct nameidata *nd, struct path *path) +{ + size_t len; + len = i_size_read(path->dentry->d_inode); + if (((size_t)len != len) || ((ssize_t)len != len)) + return -EFBIG; + + return __union_copyup_len(nd, path, len); +} + +/* + * Helper function to copy up part of a file + */ +int union_copyup_len(struct nameidata *nd, struct path *path, size_t len) +{ + return do_union_copyup_len(nd, path, 0, len); +} diff --git a/fs/union.h b/fs/union.h index 80c2421..01fa183 100644 --- a/fs/union.h +++ b/fs/union.h @@ -59,7 +59,9 @@ int needs_lookup_union(struct path *, struct path *); int union_create_topmost_dir(struct path *, struct qstr *, struct path *, struct path *); extern int union_copyup_dir(struct path *); - +extern int union_copyup(struct nameidata *, struct path *); +extern int __union_copyup(struct nameidata *, struct path *); +extern int union_copyup_len(struct nameidata *, struct path *, size_t len); #else /* CONFIG_UNION_MOUNT */ #define IS_MNT_UNION(x) (0) @@ -69,6 +71,9 @@ extern int union_copyup_dir(struct path *); #define needs_lookup_union(x, y) ({ (0); }) #define union_create_topmost_dir(w, x, y, z) ({ BUG(); (NULL); }) #define union_copyup_dir(x) ({ BUG(); (0); }) +#define union_copyup(x, y) ({ BUG(); (NULL); }) +#define __union_copyup(x, y) ({ BUG(); (NULL); }) +#define union_copyup_len(x, y, z) ({ BUG(); (NULL); }) #endif /* CONFIG_UNION_MOUNT */ #endif /* __KERNEL__ */ -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/