I have modified the following two points from the previous version.
These are suggested by Christoph Hellwig.
o Two helper functions for ioctls (ioctl_freeze and ioctl_thaw) are
added for the readability.
o The semaphore for the freeze operation is replaced with new bit
flag (bd_state) for the efficiency of the locking.
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 <t-sato@xxxxxxxxxxxxx>
Signed-off-by: Masayuki Hamaguchi <m-hamaguchi@xxxxxxxxxxxxx>
---
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-2.6.26-rc2.org/fs/buffer.c linux-2.6.26-rc2-bit/fs/buffer.c
--- linux-2.6.26-rc2.org/fs/buffer.c 2008-05-12 09:09:41.000000000 +0900
+++ linux-2.6.26-rc2-bit/fs/buffer.c 2008-05-12 11:20:19.000000000 +0900
@@ -201,6 +201,21 @@ struct super_block *freeze_bdev(struct b
{
struct super_block *sb;
+ if (test_and_set_bit(BD_FREEZE_OP, &bdev->bd_state))
+ return ERR_PTR(-EBUSY);
+
+ sb = get_super_without_lock(bdev);
+
+ /* If super_block has been already frozen, return. */
+ if (sb && sb->s_frozen != SB_UNFROZEN) {
+ put_super(sb);
+ clear_bit(BD_FREEZE_OP, &bdev->bd_state);
+ 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 +234,8 @@ struct super_block *freeze_bdev(struct b
}
sync_blockdev(bdev);
+ clear_bit(BD_FREEZE_OP, &bdev->bd_state);
+
return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
}
EXPORT_SYMBOL(freeze_bdev);
@@ -230,8 +247,17 @@ 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)
{
+
+ if (test_and_set_bit(BD_FREEZE_OP, &bdev->bd_state))
+ return -EBUSY;
+
+ if (sb && sb->s_frozen == SB_UNFROZEN) {
+ clear_bit(BD_FREEZE_OP, &bdev->bd_state);
+ return 0;
+ }
+
if (sb) {
BUG_ON(sb->s_bdev != bdev);
@@ -244,6 +270,8 @@ void thaw_bdev(struct block_device *bdev
}
up(&bdev->bd_mount_sem);
+ clear_bit(BD_FREEZE_OP, &bdev->bd_state);
+ return 0;
}
EXPORT_SYMBOL(thaw_bdev);
diff -uprN -X /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.26-rc2.org/fs/ioctl.c linux-2.6.26-rc2-bit/fs/ioctl.c
--- linux-2.6.26-rc2.org/fs/ioctl.c 2008-05-12 09:09:41.000000000 +0900
+++ linux-2.6.26-rc2-bit/fs/ioctl.c 2008-05-13 14:33:33.000000000 +0900
@@ -13,6 +13,7 @@
#include <linux/security.h>
#include <linux/module.h>
#include <linux/uaccess.h>
+#include <linux/buffer_head.h>
#include <asm/ioctls.h>
@@ -141,6 +142,49 @@ 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 -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;
+
+ /* 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 +225,15 @@ 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 /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.26-rc2.org/fs/super.c linux-2.6.26-rc2-bit/fs/super.c
--- linux-2.6.26-rc2.org/fs/super.c 2008-05-12 09:09:41.000000000 +0900
+++ linux-2.6.26-rc2-bit/fs/super.c 2008-05-12 11:20:19.000000000 +0900
@@ -156,7 +156,7 @@ 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);
@@ -509,6 +509,36 @@ 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-2.6.26-rc2.org/include/linux/buffer_head.h linux-2.6.26-rc2-bit
/include/linux/buffer_head.h
--- linux-2.6.26-rc2.org/include/linux/buffer_head.h 2008-05-12 09:09:41.000000000 +0900
+++ linux-2.6.26-rc2-bit/include/linux/buffer_head.h 2008-05-12 11:20:19.000000000 +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 /home/sho/pub/MC/freeze-set/dontdiff linux-2.6.26-rc2.org/include/linux/fs.h linux-2.6.26-rc2-bit/include/
linux/fs.h
--- linux-2.6.26-rc2.org/include/linux/fs.h 2008-05-12 09:09:41.000000000 +0900
+++ linux-2.6.26-rc2-bit/include/linux/fs.h 2008-05-12 11:20:19.000000000 +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)
@@ -494,6 +496,13 @@ int pagecache_write_end(struct file *, s
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata);
+/*
+ * Bits in block_device.bd_state.
+ */
+enum bd_state {
+ BD_FREEZE_OP /* In freeze operation */
+};
+
struct backing_dev_info;
struct address_space {
struct inode *host; /* owner: inode, block_device */
@@ -547,6 +556,9 @@ struct block_device {
* care to not mess up bd_private for that case.
*/
unsigned long bd_private;
+
+ /* State of the block device. (Used by freeze feature) */
+ unsigned long bd_state;
};
/*
@@ -1964,7 +1976,9 @@ 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);
--
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