Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752418Ab0GMDwa (ORCPT ); Mon, 12 Jul 2010 23:52:30 -0400 Received: from out1.smtp.messagingengine.com ([66.111.4.25]:46192 "EHLO out1.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751399Ab0GMDw2 (ORCPT ); Mon, 12 Jul 2010 23:52:28 -0400 X-Sasl-enc: 01XQ4sWvJN3fPP+x4ca11oyg4m4k1VFQE6njgCWNMMJ7 1278993145 Date: Tue, 13 Jul 2010 11:52:19 +0800 From: Ian Kent To: Valerie Aurora Cc: Alexander Viro , Miklos Szeredi , Jan Blunck , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, David Woodhouse Subject: Re: [PATCH 06/38] whiteout: Add vfs_whiteout() and whiteout inode operation Message-ID: <20100713035217.GA3949@zeus.themaw.net> References: <1276627208-17242-1-git-send-email-vaurora@redhat.com> <1276627208-17242-7-git-send-email-vaurora@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1276627208-17242-7-git-send-email-vaurora@redhat.com> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8684 Lines: 234 Couple of comments below. On Tue, Jun 15, 2010 at 11:39:36AM -0700, Valerie Aurora wrote: > From: Jan Blunck > > Whiteout a given directory entry. File systems that support whiteouts > must implement the new ->whiteout() directory inode operation. > > XXX - Only whiteout when there is a matching entry in a lower layer. > > XXX - MS_WHITEOUT only indicates whiteouts, but we also use it for > fallthrus. Can we just check root->i_op->whiteout and ->fallthru? Or > do we need an MS_FALLTHRU? > > Signed-off-by: Jan Blunck > Signed-off-by: David Woodhouse > Signed-off-by: Valerie Aurora > --- > Documentation/filesystems/vfs.txt | 10 +++++- > fs/dcache.c | 4 ++- > fs/namei.c | 73 ++++++++++++++++++++++++++++++++++++- > include/linux/dcache.h | 6 +++ > include/linux/fs.h | 2 + > 5 files changed, 92 insertions(+), 3 deletions(-) > > diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt > index 3de2f32..8846b4f 100644 > --- a/Documentation/filesystems/vfs.txt > +++ b/Documentation/filesystems/vfs.txt > @@ -308,7 +308,7 @@ struct inode_operations > ----------------------- > > This describes how the VFS can manipulate an inode in your > -filesystem. As of kernel 2.6.22, the following members are defined: > +filesystem. As of kernel 2.6.33, the following members are defined: > > struct inode_operations { > int (*create) (struct inode *,struct dentry *,int, struct nameidata *); > @@ -319,6 +319,7 @@ struct inode_operations { > int (*mkdir) (struct inode *,struct dentry *,int); > int (*rmdir) (struct inode *,struct dentry *); > int (*mknod) (struct inode *,struct dentry *,int,dev_t); > + int (*whiteout) (struct inode *, struct dentry *, struct dentry *); > int (*rename) (struct inode *, struct dentry *, > struct inode *, struct dentry *); > int (*readlink) (struct dentry *, char __user *,int); > @@ -382,6 +383,13 @@ otherwise noted. > will probably need to call d_instantiate() just as you would > in the create() method > > + whiteout: called by the rmdir(2) and unlink(2) system calls on a > + layered file system. Only required if you want to support > + whiteouts. The first dentry passed in is that for the old > + dentry if it exists, and a negative dentry otherwise. The > + second is the dentry for the whiteout itself. This method > + must unlink() or rmdir() the original entry if it exists. > + > rename: called by the rename(2) system call to rename the object to > have the parent and name given by the second inode and dentry. > > diff --git a/fs/dcache.c b/fs/dcache.c > index f1358e5..265015d 100644 > --- a/fs/dcache.c > +++ b/fs/dcache.c > @@ -992,8 +992,10 @@ EXPORT_SYMBOL(d_alloc_name); > /* the caller must hold dcache_lock */ > static void __d_instantiate(struct dentry *dentry, struct inode *inode) > { > - if (inode) > + if (inode) { > + dentry->d_flags &= ~DCACHE_WHITEOUT; > list_add(&dentry->d_alias, &inode->i_dentry); > + } > dentry->d_inode = inode; > fsnotify_d_instantiate(dentry, inode); > } > diff --git a/fs/namei.c b/fs/namei.c > index f731108..2c723e2 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -1356,7 +1356,6 @@ static int may_delete(struct inode *dir,struct dentry *victim,int isdir) > if (!victim->d_inode) > return -ENOENT; > > - BUG_ON(victim->d_parent->d_inode != dir); > audit_inode_child(victim, dir); > > error = inode_permission(dir, MAY_WRITE | MAY_EXEC); > @@ -2168,6 +2167,78 @@ SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode) > return sys_mkdirat(AT_FDCWD, pathname, mode); > } > > +/** > + * vfs_whiteout: create a whiteout for the given directory entry > + * @dir: parent inode > + * @dentry: directory entry to whiteout > + * > + * Create a whiteout for the given directory entry. A whiteout > + * prevents lookup from dropping down to a lower layer of a union > + * mounted file system. > + * > + * There are two important cases: (a) The directory entry to be > + * whited-out may already exist, in which case it must first be > + * deleted before we create the whiteout, and (b) no such directory > + * entry exists and we only have to create the whiteout itself. > + * > + * The caller must pass in a dentry for the directory entry to be > + * whited-out - a positive one if it exists, and a negative if not. > + * When this function returns, the caller should dput() the old, now > + * defunct dentry it passed in. The dentry for the whiteout itself is > + * created inside this function. > + */ > +static int vfs_whiteout(struct inode *dir, struct dentry *old_dentry, int isdir) > +{ > + int err; > + struct inode *old_inode = old_dentry->d_inode; > + struct dentry *parent, *whiteout; > + > + BUG_ON(old_dentry->d_parent->d_inode != dir); > + > + if (!dir->i_op || !dir->i_op->whiteout) > + return -EOPNOTSUPP; > + > + /* > + * If the old dentry is positive, then we have to delete this > + * entry before we create the whiteout. The file system > + * ->whiteout() op does the actual delete, but we do all the > + * VFS-level checks and changes here. > + */ > + if (old_inode) { > + mutex_lock(&old_inode->i_mutex); > + if (d_mountpoint(old_dentry)) { > + mutex_unlock(&old_inode->i_mutex); > + return -EBUSY; > + } > + if (isdir) { > + dentry_unhash(old_dentry); > + err = security_inode_rmdir(dir, old_dentry); > + } else { > + err = security_inode_unlink(dir, old_dentry); One to many tabs. > + } > + } > + > + parent = dget_parent(old_dentry); > + whiteout = d_alloc_name(parent, old_dentry->d_name.name); > + > + if (!err) > + err = dir->i_op->whiteout(dir, old_dentry, whiteout); err may be used unitialized. > + > + if (old_inode) { > + mutex_unlock(&old_inode->i_mutex); > + if (!err) { > + fsnotify_link_count(old_inode); > + d_delete(old_dentry); > + } > + if (isdir) > + dput(old_dentry); > + } > + > + dput(whiteout); > + dput(parent); > + return err; > +} > + > /* > * We try to drop the dentry early: we should have > * a usage count of 2 if we're the only user of this > diff --git a/include/linux/dcache.h b/include/linux/dcache.h > index eebb617..630baef 100644 > --- a/include/linux/dcache.h > +++ b/include/linux/dcache.h > @@ -183,6 +183,7 @@ d_iput: no no no yes > #define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched by inotify */ > > #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */ > +#define DCACHE_WHITEOUT 0x0080 /* This negative dentry is a whiteout */ > > #define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */ DCACHE_WHITEOUT == DCACHE_FSNOTIFY_PARENT_WATCHED, is that intended? > > @@ -372,6 +373,11 @@ static inline void dont_mount(struct dentry *dentry) > spin_unlock(&dentry->d_lock); > } > > +static inline int d_is_whiteout(struct dentry *dentry) > +{ > + return (dentry->d_flags & DCACHE_WHITEOUT); > +} > + > static inline struct dentry *dget_parent(struct dentry *dentry) > { > struct dentry *ret; > diff --git a/include/linux/fs.h b/include/linux/fs.h > index d7ef72a..7afdbd4 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -209,6 +209,7 @@ struct inodes_stat_t { > #define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */ > #define MS_I_VERSION (1<<23) /* Update inode I_version field */ > #define MS_STRICTATIME (1<<24) /* Always perform atime updates */ > +#define MS_WHITEOUT (1<<25) /* FS supports whiteout filetype */ > #define MS_ACTIVE (1<<30) > #define MS_NOUSER (1<<31) > > @@ -1527,6 +1528,7 @@ struct inode_operations { > int (*mkdir) (struct inode *,struct dentry *,int); > int (*rmdir) (struct inode *,struct dentry *); > int (*mknod) (struct inode *,struct dentry *,int,dev_t); > + int (*whiteout) (struct inode *, struct dentry *, struct dentry *); > int (*rename) (struct inode *, struct dentry *, > struct inode *, struct dentry *); > int (*readlink) (struct dentry *, char __user *,int); > -- > 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/ -- 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/