From: Takashi Sato Subject: [RFC PATCH 1/3] Implement generic freeze feature Date: Tue, 1 Apr 2008 21:17:29 +0900 Message-ID: <20080401211729t-sato@mail.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: "linux-ext4@vger.kernel.org" , "xfs@oss.sgi.com" , "linux-fsdevel@vger.kernel.org" , "dm-devel@redhat.com" , "linux-kernel@vger.kernel.org" To: David Chinner Return-path: Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org The ioctls for the generic freeze feature are below. o Freeze the filesystem int ioctl(int fd, int FIFREEZE, arg) fd: The file descriptor of the mountpoint FIFREEZE: request code for the freeze arg: Ignored Return value: 0 if the operation succeeds. Otherwise, -1 o Unfreeze the filesystem int ioctl(int fd, int FITHAW, arg) fd: The file descriptor of the mountpoint FITHAW: request code for unfreeze arg: Ignored Return value: 0 if the operation succeeds. Otherwise, -1 Signed-off-by: Takashi Sato Signed-off-by: Masayuki Hamaguchi --- fs/block_dev.c | 3 +++ fs/buffer.c | 25 +++++++++++++++++++++++++ fs/ioctl.c | 35 +++++++++++++++++++++++++++++++++++ fs/super.c | 32 +++++++++++++++++++++++++++++++- include/linux/fs.h | 7 +++++++ 5 files changed, 101 insertions(+), 1 deletion(-) diff -uprN -X /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.25-rc7.org/fs/block_dev.c linux-2.6.25-rc7-freeze/fs/block_ dev.c --- linux-2.6.25-rc7.org/fs/block_dev.c 2008-03-26 10:38:14.000000000 +0900 +++ linux-2.6.25-rc7-freeze/fs/block_dev.c 2008-03-27 09:26:36.000000000 +0900 @@ -284,6 +284,9 @@ static void init_once(struct kmem_cache INIT_LIST_HEAD(&bdev->bd_holder_list); #endif inode_init_once(&ei->vfs_inode); + + /* Initialize semaphore for freeze. */ + sema_init(&bdev->bd_freeze_sem, 1); } static inline void __bd_forget(struct inode *inode) diff -uprN -X /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.25-rc7.org/fs/buffer.c linux-2.6.25-rc7-freeze/fs/buffer.c --- linux-2.6.25-rc7.org/fs/buffer.c 2008-03-26 10:38:14.000000000 +0900 +++ linux-2.6.25-rc7-freeze/fs/buffer.c 2008-03-26 20:32:23.000000000 +0900 @@ -201,6 +201,19 @@ struct super_block *freeze_bdev(struct b { struct super_block *sb; + down(&bdev->bd_freeze_sem); + sb = get_super_without_lock(bdev); + + /* If super_block has been already frozen, return. */ + if (sb && sb->s_frozen != SB_UNFROZEN) { + put_super(sb); + up(&bdev->bd_freeze_sem); + return sb; + } + + if (sb) + put_super(sb); + down(&bdev->bd_mount_sem); sb = get_super(bdev); if (sb && !(sb->s_flags & MS_RDONLY)) { @@ -219,6 +232,9 @@ struct super_block *freeze_bdev(struct b } sync_blockdev(bdev); + + up(&bdev->bd_freeze_sem); + return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */ } EXPORT_SYMBOL(freeze_bdev); @@ -232,6 +248,13 @@ EXPORT_SYMBOL(freeze_bdev); */ void thaw_bdev(struct block_device *bdev, struct super_block *sb) { + down(&bdev->bd_freeze_sem); + + if (sb && sb->s_frozen == SB_UNFROZEN) { + up(&bdev->bd_freeze_sem); + return; + } + if (sb) { BUG_ON(sb->s_bdev != bdev); @@ -244,6 +267,8 @@ void thaw_bdev(struct block_device *bdev } up(&bdev->bd_mount_sem); + + up(&bdev->bd_freeze_sem); } EXPORT_SYMBOL(thaw_bdev); diff -uprN -X /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.25-rc7.org/fs/ioctl.c linux-2.6.25-rc7-freeze/fs/ioctl.c --- linux-2.6.25-rc7.org/fs/ioctl.c 2008-03-26 10:38:14.000000000 +0900 +++ linux-2.6.25-rc7-freeze/fs/ioctl.c 2008-03-26 20:22:17.000000000 +0900 @@ -13,6 +13,7 @@ #include #include #include +#include #include @@ -181,6 +182,40 @@ int do_vfs_ioctl(struct file *filp, unsi } else error = -ENOTTY; break; + + case FIFREEZE: { + struct super_block *sb = filp->f_path.dentry->d_inode->i_sb; + + if (!capable(CAP_SYS_ADMIN)) { + error = -EPERM; + break; + } + + /* If filesystem doesn't support freeze feature, return. */ + if (sb->s_op->write_super_lockfs == NULL) { + error = -EINVAL; + break; + } + + /* Freeze. */ + freeze_bdev(sb->s_bdev); + + break; + } + + case FITHAW: { + struct super_block *sb = filp->f_path.dentry->d_inode->i_sb; + + if (!capable(CAP_SYS_ADMIN)) { + error = -EPERM; + break; + } + + /* Thaw. */ + thaw_bdev(sb->s_bdev, sb); + break; + } + default: if (S_ISREG(filp->f_path.dentry->d_inode->i_mode)) error = file_ioctl(filp, cmd, arg); diff -uprN -X /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.25-rc7.org/fs/super.c linux-2.6.25-rc7-freeze/fs/super.c --- linux-2.6.25-rc7.org/fs/super.c 2008-03-26 10:38:14.000000000 +0900 +++ linux-2.6.25-rc7-freeze/fs/super.c 2008-03-26 20:23:21.000000000 +0900 @@ -154,7 +154,7 @@ int __put_super_and_need_restart(struct * Drops a temporary reference, frees superblock if there's no * references left. */ -static void put_super(struct super_block *sb) +void put_super(struct super_block *sb) { spin_lock(&sb_lock); __put_super(sb); @@ -507,6 +507,36 @@ rescan: EXPORT_SYMBOL(get_super); +/* + * get_super_without_lock - Get super_block from block_device without lock. + * @bdev: block device struct + * + * Scan the superblock list and finds the superblock of the file system + * mounted on the block device given. This doesn't lock anyone. + * %NULL is returned if no match is found. + */ +struct super_block *get_super_without_lock(struct block_device *bdev) +{ + struct super_block *sb; + + if (!bdev) + return NULL; + + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (sb->s_bdev == bdev) { + if (sb->s_root) { + sb->s_count++; + spin_unlock(&sb_lock); + return sb; + } + } + } + spin_unlock(&sb_lock); + return NULL; +} +EXPORT_SYMBOL(get_super_without_lock); + struct super_block * user_get_super(dev_t dev) { struct super_block *sb; diff -uprN -X /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.25-rc7.org/include/linux/fs.h linux-2.6.25-rc7-freeze/inclu de/linux/fs.h --- linux-2.6.25-rc7.org/include/linux/fs.h 2008-03-26 10:38:14.000000000 +0900 +++ linux-2.6.25-rc7-freeze/include/linux/fs.h 2008-03-26 20:27:44.000000000 +0900 @@ -223,6 +223,8 @@ extern int dir_notify_enable; #define BMAP_IOCTL 1 /* obsolete - kept for compatibility */ #define FIBMAP _IO(0x00,1) /* bmap access */ #define FIGETBSZ _IO(0x00,2) /* get the block size used for bmap */ +#define FIFREEZE _IOWR('X', 119, int) /* Freeze */ +#define FITHAW _IOWR('X', 120, int) /* Thaw */ #define FS_IOC_GETFLAGS _IOR('f', 1, long) #define FS_IOC_SETFLAGS _IOW('f', 2, long) @@ -548,6 +550,9 @@ struct block_device { * care to not mess up bd_private for that case. */ unsigned long bd_private; + + /* Semaphore for freeze */ + struct semaphore bd_freeze_sem; }; /* @@ -1926,7 +1931,9 @@ extern int do_vfs_ioctl(struct file *fil extern void get_filesystem(struct file_system_type *fs); extern void put_filesystem(struct file_system_type *fs); extern struct file_system_type *get_fs_type(const char *name); +extern void put_super(struct super_block *sb); extern struct super_block *get_super(struct block_device *); +extern struct super_block *get_super_without_lock(struct block_device *); extern struct super_block *user_get_super(dev_t); extern void drop_super(struct super_block *sb);