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Registered in England and Wales under Company Registration No. 3798903 From: David Howells Subject: [PATCH 13/73] whiteout: Add vfs_whiteout() and whiteout inode operation [ver #2] To: linux-fsdevel@vger.kernel.org, viro@ZenIV.linux.org.uk, valerie.aurora@gmail.com Cc: linux-kernel@vger.kernel.org, Jan Blunck (Original author), David Woodhouse , Valerie Aurora , David Howells (Forward port) Date: Tue, 21 Feb 2012 17:59:05 +0000 Message-ID: <20120221175905.25235.97225.stgit@warthog.procyon.org.uk> In-Reply-To: <20120221175721.25235.8901.stgit@warthog.procyon.org.uk> References: <20120221175721.25235.8901.stgit@warthog.procyon.org.uk> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8011 Lines: 222 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. Signed-off-by: Jan Blunck (Original author) Signed-off-by: David Woodhouse Signed-off-by: Valerie Aurora Signed-off-by: David Howells (Forward port) --- Documentation/filesystems/vfs.txt | 10 ++++ fs/dcache.c | 1 fs/namei.c | 89 +++++++++++++++++++++++++++++++++++++ include/linux/dcache.h | 6 ++ include/linux/fs.h | 2 + 5 files changed, 106 insertions(+), 2 deletions(-) diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 3d9393b..8575c5b 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -338,7 +338,7 @@ 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 2.6.34, the following members are defined: struct inode_operations { int (*create) (struct inode *,struct dentry *, umode_t, struct nameidata *); @@ -349,6 +349,7 @@ struct inode_operations { int (*mkdir) (struct inode *,struct dentry *,umode_t); int (*rmdir) (struct inode *,struct dentry *); int (*mknod) (struct inode *,struct dentry *,umode_t,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); @@ -413,6 +414,13 @@ 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 fe19ac1..a8355d5 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1311,6 +1311,7 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode) { spin_lock(&dentry->d_lock); if (inode) { + dentry->d_flags &= ~DCACHE_WHITEOUT; if (unlikely(IS_AUTOMOUNT(inode))) dentry->d_flags |= DCACHE_NEED_AUTOMOUNT; list_add(&dentry->d_alias, &inode->i_dentry); diff --git a/fs/namei.c b/fs/namei.c index 7f9df02..3d396fd 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1948,7 +1948,6 @@ 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); @@ -2647,6 +2646,94 @@ SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, 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) +{ + struct inode *old_inode = old_dentry->d_inode; + struct dentry *parent, *whiteout; + bool do_dput = false; + int err = 0; + + 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) + err = security_inode_rmdir(dir, old_dentry); + else + err = security_inode_unlink(dir, old_dentry); + if (err) + goto error_unlock; + } + + parent = dget_parent(old_dentry); + err = -ENOMEM; + whiteout = d_alloc_name(parent, old_dentry->d_name.name); + if (!whiteout) + goto error_put_parent; + + if (old_inode && isdir) { + dentry_unhash(old_dentry); + do_dput = true; + } + + err = dir->i_op->whiteout(dir, old_dentry, whiteout); + if (err) + goto error_put_whiteout; + + if (old_inode) { + mutex_unlock(&old_inode->i_mutex); + fsnotify_link_count(old_inode); + d_delete(old_dentry); + if (do_dput) + dput(old_dentry); + } + + dput(whiteout); + dput(parent); + return err; + +error_put_whiteout: + dput(whiteout); +error_put_parent: + dput(parent); +error_unlock: + if (old_inode) + mutex_unlock(&old_inode->i_mutex); + if (do_dput) + dput(old_dentry); + return err; +} + /* * The dentry_unhash() helper will 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 d64a55b..f22f530 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -204,6 +204,7 @@ struct dentry_operations { #define DCACHE_CANT_MOUNT 0x0100 #define DCACHE_GENOCIDE 0x0200 #define DCACHE_SHRINK_LIST 0x0400 +#define DCACHE_WHITEOUT 0x0800 /* Stop lookup in a unioned file system */ #define DCACHE_NFSFS_RENAMED 0x1000 /* this dentry has been "silly renamed" and has to be deleted on the last @@ -414,6 +415,11 @@ static inline bool d_managed(struct dentry *dentry) return dentry->d_flags & DCACHE_MANAGED_DENTRY; } +static inline int d_is_whiteout(struct dentry *dentry) +{ + return dentry->d_flags & DCACHE_WHITEOUT; +} + static inline bool d_mountpoint(struct dentry *dentry) { return dentry->d_flags & DCACHE_MOUNTED; diff --git a/include/linux/fs.h b/include/linux/fs.h index ab36080..1e4ae06 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -210,6 +210,7 @@ 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_NOSEC (1<<28) #define MS_BORN (1<<29) #define MS_ACTIVE (1<<30) @@ -1651,6 +1652,7 @@ struct inode_operations { int (*mkdir) (struct inode *,struct dentry *,umode_t); int (*rmdir) (struct inode *,struct dentry *); int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t); + int (*whiteout) (struct inode *, struct dentry *, struct dentry *); int (*rename) (struct inode *, struct dentry *, struct inode *, struct dentry *); void (*truncate) (struct inode *); -- 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/