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Add timeout feature

PATCH In review Takashi Sato 1 participant 1 message Sep 26, 2008

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VFS Device mapper XFS filesystem Landlock security module
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Takashi Sato

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PATCH 10/10 Add timeout feature

The timeout feature is added to "freeze ioctl" to solve a deadlock when the freezer accesses a frozen filesystem. And new ioctl to reset the timeout period is added to extend the timeout period. For example, the freezer resets the timeout period to 10 seconds every 5 seconds. In this approach, even if the freezer causes a deadlock by accessing the frozen filesystem, it will be solved by the timeout in 10 seconds and the freezer will be able to recognize that at the next reset of timeout period.
o Freeze the filesystem
int ioctl(int fd, int FIFREEZE, long *timeout_sec)
fd: The file descriptor of the mountpoint
FIFREEZE: request code for the freeze
timeout_sec: the timeout period in seconds
If it's 0 or 1, the timeout isn't set.
This special case of "1" is implemented to keep the compatibility with XFS applications.
Return value: 0 if the operation succeeds. Otherwise, -1

o Reset the timeout period
int ioctl(int fd, int FIFREEZE_RESET_TIMEOUT, long *timeout_sec)
fd:file descriptor of mountpoint
FIFREEZE_RESET_TIMEOUT: request code for reset of timeout period
timeout_sec: new timeout period in seconds
Return value: 0 if the operation succeeds. Otherwise, -1 Error number: If the filesystem has already been unfrozen,
errno is set to EINVAL.

Signed-off-by Takashi Sato <[email protected]>
Signed-off-by Masayuki Hamaguchi <[email protected]>
---
 drivers/md/dm.c             |    2 -
 fs/block_dev.c              |    2 +
 fs/buffer.c                 |   44 ++++++++++++++++++++++++---
 fs/ioctl.c                  |   71 ++++++++++++++++++++++++++++++++++++++++++--
 fs/super.c                  |   37 ++++++++++++++++++++++
 fs/xfs/xfs_fsops.c          |    2 -
 include/linux/buffer_head.h |    4 +-
 include/linux/fs.h          |    8 ++++
 8 files changed, 159 insertions(+), 11 deletions(-)

diff -uprN -X linux-2.6.27-rc7-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/drivers/md/dm.c linux-2.6.27-rc7-timeout/ drivers/md/dm.c

drivers/md/dm.c +1 -1
@@ -1451,7 +1451,7 @@ static int lock_fs(struct mapped_device 
 
 	WARN_ON(md->frozen_sb);
 
-	md->frozen_sb = freeze_bdev(md->suspended_bdev);
+	md->frozen_sb = freeze_bdev(md->suspended_bdev, 0);
 	if (IS_ERR(md->frozen_sb)) {
 		r = PTR_ERR(md->frozen_sb);
 		md->frozen_sb = NULL;

diff -uprN -X linux-2.6.27-rc7-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/fs/block_dev.c linux-2.6.27-rc7-timeout/f s/block_dev.c

fs/block_dev.c +2 -0
@@ -287,6 +287,8 @@ static void init_once(void *foo)
 	inode_init_once(&ei->vfs_inode);
 	/* Initialize mutex for freeze. */
 	mutex_init(&bdev->bd_fsfreeze_mutex);
+	/* Setup freeze timeout function. */
+	INIT_DELAYED_WORK(&bdev->bd_fsfreeze_timeout, fsfreeze_timeout);
 }
 
 static inline void __bd_forget(struct inode *inode)

diff -uprN -X linux-2.6.27-rc7-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/fs/buffer.c linux-2.6.27-rc7-timeout/fs/b uffer.c

fs/buffer.c +39 -5

91 lines not on this page · raw message

diff -uprN -X linux-2.6.27-rc7-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/fs/ioctl.c linux-2.6.27-rc7-timeout/fs/io ctl.c

fs/ioctl.c +68 -3

104 lines not on this page · raw message

diff -uprN -X linux-2.6.27-rc7-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/fs/super.c linux-2.6.27-rc7-timeout/fs/su per.c

fs/super.c +37 -0
@@ -981,3 +981,40 @@ struct vfsmount *kern_mount_data(struct 
 }
 
 EXPORT_SYMBOL_GPL(kern_mount_data);
+
+/*
+ * fsfreeze_timeout - Thaw the filesystem.
+ *
+ * @work:	work queue (delayed_work.work)
+ *
+ * Called by the delayed work when elapsing the timeout period.
+ * Thaw the filesystem.
+ */
+void fsfreeze_timeout(struct work_struct *work)
+{
+	struct block_device *bd = container_of(work,
+			struct block_device, bd_fsfreeze_timeout.work);
+	struct super_block *sb = get_super(bd);
+
+	thaw_bdev_core(bd, sb, 0);
+
+	if (sb)
+		drop_super(sb);
+}
+
+/*
+ * add_fsfreeze_timeout - Add timeout for freeze.
+ *
+ * @bdev:		block device struct
+ * @timeout_msec:	timeout period
+ *
+ * Add the delayed work for freeze timeout to the delayed work queue.
+ */
+void add_fsfreeze_timeout(struct block_device *bdev, unsigned int timeout_msec)
+{
+	s64 timeout_jiffies = msecs_to_jiffies(timeout_msec);
+
+	/* Set delayed work queue */
+	cancel_delayed_work_sync(&bdev->bd_fsfreeze_timeout);
+	schedule_delayed_work(&bdev->bd_fsfreeze_timeout, timeout_jiffies);
+}

diff -uprN -X linux-2.6.27-rc7-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/fs/xfs/xfs_fsops.c linux-2.6.27-rc7-timeo ut/fs/xfs/xfs_fsops.c

fs/xfs/xfs_fsops.c +1 -1
@@ -624,7 +624,7 @@ xfs_fs_goingdown(
 {
 	switch (inflags) {
 	case XFS_FSOP_GOING_FLAGS_DEFAULT: {
-		struct super_block *sb = freeze_bdev(mp->m_super->s_bdev);
+		struct super_block *sb = freeze_bdev(mp->m_super->s_bdev, 0);
 
 		if (sb && !IS_ERR(sb)) {
 			xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);

diff -uprN -X linux-2.6.27-rc7-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/include/linux/buffer_head.h linux-2.6.27- rc7-timeout/include/linux/buffer_head.h

include/linux/buffer_head.h +3 -1
@@ -169,8 +169,10 @@ int sync_blockdev(struct block_device *b
 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 *);
+struct super_block *freeze_bdev(struct block_device *,
+				unsigned int timeout_msec);
 int thaw_bdev(struct block_device *, struct super_block *);
+int thaw_bdev_core(struct block_device *, struct super_block *, int);
 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-xfs/Documentation/dontdiff linux-2.6.27-rc7-xfs/include/linux/fs.h linux-2.6.27-rc7-timeo ut/include/linux/fs.h

include/linux/fs.h +8 -0
@@ -8,6 +8,7 @@
 
 #include <linux/limits.h>
 #include <linux/ioctl.h>
+#include <linux/workqueue.h>
 
 /*
  * It's silly to have NR_OPEN bigger than NR_FILE, but you can change

@@ -228,6 +229,7 @@ extern int dir_notify_enable;
 #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	FIFREEZE_RESET_TIMEOUT	_IO(0x00, 3)	/* Reset freeze timeout */
 
 #define	FS_IOC_GETFLAGS			_IOR('f', 1, long)
 #define	FS_IOC_SETFLAGS			_IOW('f', 2, long)

@@ -581,6 +583,8 @@ struct block_device {
 	int			bd_fsfreeze_count;
 	/* Mutex for freeze */
 	struct mutex		bd_fsfreeze_mutex;
+	/* Delayed work for freeze */
+	struct delayed_work	bd_fsfreeze_timeout;
 };
 
 /*

@@ -2160,5 +2164,9 @@ int proc_nr_files(struct ctl_table *tabl
 
 int get_filesystem_list(char * buf);
 
+extern void add_fsfreeze_timeout(struct block_device *bdev,
+				unsigned int timeout_msec);
+extern void fsfreeze_timeout(struct work_struct *work);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_FS_H */