From: Takashi Sato Subject: [PATCH 8/10] Implement generic freeze feature Date: Fri, 26 Sep 2008 17:59:12 +0900 Message-ID: <20080926175912t-sato__30981.8291957074$1222419729$gmane$org@mail.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: "linux-kernel@vger.kernel.org" To: Andrew Morton , Christoph Hellwig , "linux-fsdevel@vger.kernel.org" , "dm-devel@redhat.com" Received: from TYO201.gate.nec.co.jp ([202.32.8.193]:61106 "EHLO tyo201.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755415AbYIZI7d (ORCPT ); Fri, 26 Sep 2008 04:59:33 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 | 74 ++++++++++++++++++++++++++++++++++++++------ fs/ioctl.c | 47 +++++++++++++++++++++++++++ include/linux/buffer_head.h | 2 - include/linux/fs.h | 7 ++++ 5 files changed, 122 insertions(+), 10 deletions(-) diff -uprN -X linux-2.6.27-rc7-lockfs-jfs/Documentation/dontdiff linux-2.6.27-rc7-lockfs-jfs/fs/block_dev.c linux-2.6.27 -rc7-freeze/fs/block_dev.c --- linux-2.6.27-rc7-lockfs-jfs/fs/block_dev.c 2008-09-22 07:29:55.000000000 +0900 +++ linux-2.6.27-rc7-freeze/fs/block_dev.c 2008-09-26 20:57:53.000000000 +0900 @@ -285,6 +285,8 @@ static void init_once(void *foo) INIT_LIST_HEAD(&bdev->bd_holder_list); #endif inode_init_once(&ei->vfs_inode); + /* Initialize mutex for freeze. */ + mutex_init(&bdev->bd_fsfreeze_mutex); } static inline void __bd_forget(struct inode *inode) diff -uprN -X linux-2.6.27-rc7-lockfs-jfs/Documentation/dontdiff linux-2.6.27-rc7-lockfs-jfs/fs/buffer.c linux-2.6.27-rc 7-freeze/fs/buffer.c --- linux-2.6.27-rc7-lockfs-jfs/fs/buffer.c 2008-09-26 20:56:46.000000000 +0900 +++ linux-2.6.27-rc7-freeze/fs/buffer.c 2008-09-26 20:58:38.000000000 +0900 @@ -196,10 +196,25 @@ int fsync_bdev(struct block_device *bdev * happen on bdev until thaw_bdev() is called. * If a superblock is found on this device, we take the s_umount semaphore * on it to make sure nobody unmounts until the snapshot creation is done. + * The reference counter (bd_fsfreeze_count) guarantees that only the last + * unfreeze process can unfreeze the frozen filesystem actually when multiple + * freeze requests arrive simultaneously. It counts up in freeze_bdev() and + * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze + * actually. */ struct super_block *freeze_bdev(struct block_device *bdev) { struct super_block *sb; + int error = 0; + + mutex_lock(&bdev->bd_fsfreeze_mutex); + if (bdev->bd_fsfreeze_count > 0) { + bdev->bd_fsfreeze_count++; + sb = get_super(bdev); + mutex_unlock(&bdev->bd_fsfreeze_mutex); + return sb; + } + bdev->bd_fsfreeze_count++; down(&bdev->bd_mount_sem); sb = get_super(bdev); @@ -214,11 +229,24 @@ struct super_block *freeze_bdev(struct b sync_blockdev(sb->s_bdev); - if (sb->s_op->freeze_fs) - sb->s_op->freeze_fs(sb); + if (sb->s_op->freeze_fs) { + error = sb->s_op->freeze_fs(sb); + if (error) { + printk(KERN_ERR + "VFS:Filesystem freeze failed\n"); + sb->s_frozen = SB_UNFROZEN; + drop_super(sb); + up(&bdev->bd_mount_sem); + bdev->bd_fsfreeze_count--; + mutex_unlock(&bdev->bd_fsfreeze_mutex); + return ERR_PTR(error); + } + } } sync_blockdev(bdev); + mutex_unlock(&bdev->bd_fsfreeze_mutex); + return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */ } EXPORT_SYMBOL(freeze_bdev); @@ -230,20 +258,48 @@ 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) { + int error = 0; + + mutex_lock(&bdev->bd_fsfreeze_mutex); + if (!bdev->bd_fsfreeze_count) { + mutex_unlock(&bdev->bd_fsfreeze_mutex); + return 0; + } + + bdev->bd_fsfreeze_count--; + if (bdev->bd_fsfreeze_count > 0) { + if (sb) + drop_super(sb); + mutex_unlock(&bdev->bd_fsfreeze_mutex); + return 0; + } + if (sb) { BUG_ON(sb->s_bdev != bdev); - - if (sb->s_op->unfreeze_fs) - sb->s_op->unfreeze_fs(sb); - sb->s_frozen = SB_UNFROZEN; - smp_wmb(); - wake_up(&sb->s_wait_unfrozen); + if (!(sb->s_flags & MS_RDONLY)) { + if (sb->s_op->unfreeze_fs) { + error = sb->s_op->unfreeze_fs(sb); + if (error) { + printk(KERN_ERR + "VFS:Filesystem thaw failed\n"); + sb->s_frozen = SB_FREEZE_TRANS; + bdev->bd_fsfreeze_count++; + mutex_unlock(&bdev->bd_fsfreeze_mutex); + return error; + } + } + sb->s_frozen = SB_UNFROZEN; + smp_wmb(); + wake_up(&sb->s_wait_unfrozen); + } drop_super(sb); } up(&bdev->bd_mount_sem); + mutex_unlock(&bdev->bd_fsfreeze_mutex); + return 0; } EXPORT_SYMBOL(thaw_bdev); diff -uprN -X linux-2.6.27-rc7-lockfs-jfs/Documentation/dontdiff linux-2.6.27-rc7-lockfs-jfs/fs/ioctl.c linux-2.6.27-rc7 -freeze/fs/ioctl.c --- linux-2.6.27-rc7-lockfs-jfs/fs/ioctl.c 2008-09-22 07:29:55.000000000 +0900 +++ linux-2.6.27-rc7-freeze/fs/ioctl.c 2008-09-26 20:57:53.000000000 +0900 @@ -13,6 +13,7 @@ #include #include #include +#include #include @@ -140,6 +141,43 @@ static int ioctl_fioasync(unsigned int f return error; } +static int ioctl_fsfreeze(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->freeze_fs == NULL) + return -EOPNOTSUPP; + + /* If a blockdevice-backed filesystem 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; +} + +static int ioctl_fsthaw(struct file *filp) +{ + struct super_block *sb = filp->f_path.dentry->d_inode->i_sb; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + /* If a blockdevice-backed filesystem 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 +219,15 @@ int do_vfs_ioctl(struct file *filp, unsi } else error = -ENOTTY; break; + + case FIFREEZE: + error = ioctl_fsfreeze(filp); + break; + + case FITHAW: + error = ioctl_fsthaw(filp); + break; + default: if (S_ISREG(filp->f_path.dentry->d_inode->i_mode)) error = file_ioctl(filp, cmd, arg); diff -uprN -X linux-2.6.27-rc7-lockfs-jfs/Documentation/dontdiff linux-2.6.27-rc7-lockfs-jfs/include/linux/buffer_head.h linux-2.6.27-rc7-freeze/include/linux/buffer_head.h --- linux-2.6.27-rc7-lockfs-jfs/include/linux/buffer_head.h 2008-09-22 07:29:55.000000000 +0900 +++ linux-2.6.27-rc7-freeze/include/linux/buffer_head.h 2008-09-26 20:57:53.000000000 +0900 @@ -170,7 +170,7 @@ 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-2.6.27-rc7-lockfs-jfs/Documentation/dontdiff linux-2.6.27-rc7-lockfs-jfs/include/linux/fs.h linux-2. 6.27-rc7-freeze/include/linux/fs.h --- linux-2.6.27-rc7-lockfs-jfs/include/linux/fs.h 2008-09-26 20:56:46.000000000 +0900 +++ linux-2.6.27-rc7-freeze/include/linux/fs.h 2008-09-26 20:57:53.000000000 +0900 @@ -226,6 +226,8 @@ 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) @@ -574,6 +576,11 @@ struct block_device { * care to not mess up bd_private for that case. */ unsigned long bd_private; + + /* The counter of freeze processes */ + int bd_fsfreeze_count; + /* Mutex for freeze */ + struct mutex bd_fsfreeze_mutex; }; /*