Freezing and thawing are separate system calls, task which is supposed
to thaw filesystem/superblock can disappear due to crash or not thaw
due to a bug. At least record task name (we can't take task_struct
reference) to make support engineer's life easier.
Hopefully 16 bytes per superblock isn't much.
TASK_COMM_LEN definition (which is userspace ABI, see prctl(PR_SET_NAME)) is
moved to userspace exported header to not drag sched.h into every fs.h inclusion.
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---
fs/block_dev.c | 12 ++++++++----
fs/ioctl.c | 22 ++++++++++++++++------
fs/super.c | 2 ++
include/linux/fs.h | 6 ++++++
include/linux/sched.h | 3 ---
include/uapi/linux/sched.h | 3 +++
6 files changed, 35 insertions(+), 13 deletions(-)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -227,9 +227,11 @@ struct super_block *freeze_bdev(struct block_device *bdev)
sb = get_active_super(bdev);
if (!sb)
goto out;
- if (sb->s_op->freeze_super)
+ if (sb->s_op->freeze_super) {
error = sb->s_op->freeze_super(sb);
- else
+ if (error == 0)
+ get_task_comm(sb->s_writers.freeze_comm, current);
+ } else
error = freeze_super(sb);
if (error) {
deactivate_super(sb);
@@ -267,9 +269,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
if (!sb)
goto out;
- if (sb->s_op->thaw_super)
+ if (sb->s_op->thaw_super) {
error = sb->s_op->thaw_super(sb);
- else
+ if (error == 0)
+ memset(sb->s_writers.freeze_comm, 0, TASK_COMM_LEN);
+ } else
error = thaw_super(sb);
if (error) {
bdev->bd_fsfreeze_count++;
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -518,6 +518,7 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
static int ioctl_fsfreeze(struct file *filp)
{
struct super_block *sb = file_inode(filp)->i_sb;
+ int rv;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -527,22 +528,31 @@ static int ioctl_fsfreeze(struct file *filp)
return -EOPNOTSUPP;
/* Freeze */
- if (sb->s_op->freeze_super)
- return sb->s_op->freeze_super(sb);
- return freeze_super(sb);
+ if (sb->s_op->freeze_super) {
+ rv = sb->s_op->freeze_super(sb);
+ if (rv == 0)
+ get_task_comm(sb->s_writers.freeze_comm, current);
+ } else
+ rv = freeze_super(sb);
+ return rv;
}
static int ioctl_fsthaw(struct file *filp)
{
struct super_block *sb = file_inode(filp)->i_sb;
+ int rv;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
/* Thaw */
- if (sb->s_op->thaw_super)
- return sb->s_op->thaw_super(sb);
- return thaw_super(sb);
+ if (sb->s_op->thaw_super) {
+ rv = sb->s_op->thaw_super(sb);
+ if (rv == 0)
+ memset(sb->s_writers.freeze_comm, 0, TASK_COMM_LEN);
+ } else
+ rv = thaw_super(sb);
+ return rv;
}
/*
--- a/fs/super.c
+++ b/fs/super.c
@@ -1351,6 +1351,7 @@ int freeze_super(struct super_block *sb)
* sees write activity when frozen is set to SB_FREEZE_COMPLETE.
*/
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
+ get_task_comm(sb->s_writers.freeze_comm, current);
up_write(&sb->s_umount);
return 0;
}
@@ -1387,6 +1388,7 @@ int thaw_super(struct super_block *sb)
out:
sb->s_writers.frozen = SB_UNFROZEN;
+ memset(sb->s_writers.freeze_comm, 0, TASK_COMM_LEN);
smp_wmb();
wake_up(&sb->s_writers.wait_unfrozen);
deactivate_locked_super(sb);
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -33,6 +33,7 @@
#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
+#include <uapi/linux/sched.h>
struct backing_dev_info;
struct export_operations;
@@ -1217,6 +1218,11 @@ struct sb_writers {
int frozen; /* Is sb frozen? */
wait_queue_head_t wait_unfrozen; /* queue for waiting for
sb to be thawed */
+ /*
+ * who froze superblock
+ * write-only field for traces in crashdump
+ */
+ char freeze_comm[TASK_COMM_LEN];
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map lock_map[SB_FREEZE_LEVELS];
#endif
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -303,9 +303,6 @@ extern char ___assert_task_state[1 - 2*!!(
#endif
-/* Task command name length */
-#define TASK_COMM_LEN 16
-
#include <linux/spinlock.h>
/*
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -49,4 +49,7 @@
*/
#define SCHED_FLAG_RESET_ON_FORK 0x01
+/* Task command name length */
+#define TASK_COMM_LEN 16
+
#endif /* _UAPI_LINUX_SCHED_H */
--
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