From: Takashi Sato Subject: [PATCH 1/3] Implement generic freeze feature Date: Tue, 22 Jul 2008 18:37:34 +0900 Message-ID: <20080722183734t-sato@mail.jp.nec.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: "linux-kernel@vger.kernel.org" To: "linux-ext4@vger.kernel.org" , "dm-devel@redhat.com" , "linux-fsdevel@vger.kernel.org" , Andrew Morton Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com List-Id: linux-ext4.vger.kernel.org When multiple freeze requests arrive simultaneously, only the last unfreeze process should unfreeze the frozen filesystem actually (as Dave Chinner, Eric Sandeen and Alasdair G Kergon commented). So I've added the reference counter to the freeze feature. It counts up in freeze_bdev() and counts down in thaw_bdev(). When it becomes "0", thaw_bdev() will unfreeze actually. 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 | 2 + fs/buffer.c | 27 ++++++++++++++++++- fs/ioctl.c | 61 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/buffer_head.h | 2 - include/linux/fs.h | 6 ++++ 5 files changed, 96 insertions(+), 2 deletions(-) diff -uprN -X linux-2.6.26.org/Documentation/dontdiff linux-2.6.26.org/fs/block_dev.c linux-2.6.26-freeze/fs/block_dev.c --- linux-2.6.26.org/fs/block_dev.c 2008-07-14 06:51:29.000000000 +0900 +++ linux-2.6.26-freeze/fs/block_dev.c 2008-07-18 15:38:03.000000000 +0900 @@ -285,6 +285,8 @@ 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 linux-2.6.26.org/Documentation/dontdiff linux-2.6.26.org/fs/buffer.c linux-2.6.26-freeze/fs/buffer.c --- linux-2.6.26.org/fs/buffer.c 2008-07-14 06:51:29.000000000 +0900 +++ linux-2.6.26-freeze/fs/buffer.c 2008-07-18 15:45:17.000000000 +0900 @@ -201,6 +201,15 @@ struct super_block *freeze_bdev(struct b { struct super_block *sb; + down(&bdev->bd_freeze_sem); + bdev->bd_freeze_count++; + if (bdev->bd_freeze_count > 1) { + sb = get_super(bdev); + drop_super(sb); + up(&bdev->bd_freeze_sem); + return sb; + } + down(&bdev->bd_mount_sem); sb = get_super(bdev); if (sb && !(sb->s_flags & MS_RDONLY)) { @@ -219,6 +228,8 @@ 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); @@ -230,8 +241,20 @@ EXPORT_SYMBOL(freeze_bdev); * * Unlocks the filesystem and marks it writeable again after freeze_bdev(). */ -void thaw_bdev(struct block_device *bdev, struct super_block *sb) +int thaw_bdev(struct block_device *bdev, struct super_block *sb) { + + down(&bdev->bd_freeze_sem); + if (!bdev->bd_freeze_count) { + up(&bdev->bd_freeze_sem); + return 0; + } + bdev->bd_freeze_count--; + if (bdev->bd_freeze_count > 0) { + up(&bdev->bd_freeze_sem); + return 0; + } + 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); + return 0; } EXPORT_SYMBOL(thaw_bdev); diff -uprN -X linux-2.6.26.org/Documentation/dontdiff linux-2.6.26.org/fs/ioctl.c linux-2.6.26-freeze/fs/ioctl.c --- linux-2.6.26.org/fs/ioctl.c 2008-07-14 06:51:29.000000000 +0900 +++ linux-2.6.26-freeze/fs/ioctl.c 2008-07-18 21:24:42.000000000 +0900 @@ -13,6 +13,7 @@ #include #include #include +#include #include @@ -141,6 +142,57 @@ static int ioctl_fioasync(unsigned int f } /* + * ioctl_freeze - Freeze the filesystem. + * + * @filp: target file + * + * Call freeze_bdev() to freeze the filesystem. + */ +static int ioctl_freeze(struct file *filp) +{ + struct super_block *sb = filp->f_path.dentry->d_inode->i_sb; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + /* If filesystem doesn't support freeze feature, return. */ + if (sb->s_op->write_super_lockfs == NULL) + return -EOPNOTSUPP; + + /* If a regular file or a directory isn't specified, return. */ + if (sb->s_bdev == NULL) + return -EINVAL; + + /* Freeze */ + sb = freeze_bdev(sb->s_bdev); + if (IS_ERR(sb)) + return PTR_ERR(sb); + return 0; +} + +/* + * ioctl_thaw - Thaw the filesystem. + * + * @filp: target file + * + * Call thaw_bdev() to thaw the filesystem. + */ +static int ioctl_thaw(struct file *filp) +{ + struct super_block *sb = filp->f_path.dentry->d_inode->i_sb; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + /* If a regular file or a directory isn't specified, return EINVAL. */ + if (sb->s_bdev == NULL) + return -EINVAL; + + /* Thaw */ + return thaw_bdev(sb->s_bdev, sb); +} + +/* * When you add any new common ioctls to the switches above and below * please update compat_sys_ioctl() too. * @@ -181,6 +233,15 @@ int do_vfs_ioctl(struct file *filp, unsi } else error = -ENOTTY; break; + + case FIFREEZE: + error = ioctl_freeze(filp); + break; + + case FITHAW: + error = ioctl_thaw(filp); + break; + default: if (S_ISREG(filp->f_path.dentry->d_inode->i_mode)) error = file_ioctl(filp, cmd, arg); diff -uprN -X linux-2.6.26.org/Documentation/dontdiff linux-2.6.26.org/include/linux/buffer_head.h linux-2.6.26-freeze/i nclude/linux/buffer_head.h --- linux-2.6.26.org/include/linux/buffer_head.h 2008-07-14 06:51:29.000000000 +0900 +++ linux-2.6.26-freeze/include/linux/buffer_head.h 2008-07-17 11:32:37.000000000 +0900 @@ -171,7 +171,7 @@ void __wait_on_buffer(struct buffer_head wait_queue_head_t *bh_waitq_head(struct buffer_head *bh); int fsync_bdev(struct block_device *); struct super_block *freeze_bdev(struct block_device *); -void thaw_bdev(struct block_device *, struct super_block *); +int thaw_bdev(struct block_device *, struct super_block *); int fsync_super(struct super_block *); int fsync_no_super(struct block_device *); struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block, diff -uprN -X linux-2.6.26.org/Documentation/dontdiff linux-2.6.26.org/include/linux/fs.h linux-2.6.26-freeze/include/li nux/fs.h --- linux-2.6.26.org/include/linux/fs.h 2008-07-14 06:51:29.000000000 +0900 +++ linux-2.6.26-freeze/include/linux/fs.h 2008-07-18 15:34:46.000000000 +0900 @@ -224,6 +224,8 @@ 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 +550,10 @@ struct block_device { * care to not mess up bd_private for that case. */ unsigned long bd_private; + /* The counter of freeze processes */ + int bd_freeze_count; + /* Semaphore for freeze */ + struct semaphore bd_freeze_sem; }; /*