Re: [Cluster-devel] [PATCH] fs: record task name which froze superblock
On Fri, Feb 20, 2015 at 01:15:22PM +0100, Jan Kara wrote:
On Fri 20-02-15 14:42:29, Alexey Dobriyan wrote:
On Wed, Feb 18, 2015 at 12:13 PM, Jan Kara j...@suse.cz wrote:
--- 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;
Why don't you just set the name in ioctl_fsfreeze() in both cases?
There are users of freeze_super() in GFS2 unless I'm misreading code.
Yes, there are. The call in fs/gfs2/glops.c is in a call path from
-freeze_super() handler for GFS2 so that one is handled in
ioctl_fsfreeze() anyway. The call in fs/gfs2/sys.c is a way to freeze
filesystem via sysfs (dunno why GFS2 has to invent its own thing and ioctl
isn't enough). Steven? So having the logic in ioctl_fsfreeze(),
freeze_bdev() and freeze_store() in gfs2 seems to be enough.
Jan, my logic is as follows.
Recording freezer task name is not filesystem/device specific and
thus should be done in generic code. So no changes in GFS2.
freeze_super() is generic counterpart to filesystem/device
specific -freeze_super() hook, look how they are paired.
It should recore freezer task name, so any future user
will not forget to do the same.
So it's in ioctl_fsfreeze(), freeze_bdev() and freeze_super().
Well, but this stores the name in two different levels - once in the top
level (ioctl_fsfreeze(), freeze_bdev()) and once in a place called from
there (freeze_super()). That just seems wrong to me. You can just record
the frozen process in freeze_super() and mandate that if someone manages to
freeze the fs without calling freeze_super() from his -freeze_super()
handler (currently there isn't such filesystem), he is also responsible for
setting freezer name... Hmm?
Jan I understand you. But I find stranger that GFS will have to record
freezer name.
I'm sending v3, hopefully final.
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1221,6 +1221,8 @@ 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 */
+ charfreeze_comm[16];
Here should be TASK_COMM_LEN, shouldn't it?
It will pull sched.h, dunno if we care about headers anymore.
That's not ideal but IMHO better than having the value hardcoded here.
That is pretty fragile - i.e. think what happens when someone decides to
increase TASK_COMM_LEN...
TASK_COMM_LEN is userspace ABI via at least prctl(PR_SET_NAME).
I can formally move it to include/uapi/linux/sched.h.
This allows to not drag sched.h into fs.h for one tiny define.
OK, moving the definition would be preferable to me (and IMO also a
cleanup).
Re: [Cluster-devel] [PATCH] fs: record task name which froze superblock
On Wed, Feb 18, 2015 at 12:13 PM, Jan Kara j...@suse.cz wrote:
On Wed 18-02-15 10:34:55, Alexey Dobriyan wrote:
On Mon, Feb 16, 2015 at 10:38:52AM +0100, Jan Kara wrote:
On Sat 14-02-15 21:55:24, Alexey Dobriyan wrote:
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. Record at least task name (we can't take task_struct
reference) to make support engineer's life easier.
Hopefully 16 bytes per superblock isn't much.
P.S.: Cc'ing GFS2 people just in case they want to correct
my understanding of GFS2 having async freeze code.
Signed-off-by: Alexey Dobriyan adobri...@gmail.com
Hum, and when do you show the task name? Or do you expect that customer
takes a crashdump and support just finds it in memory?
Yeah, having at least something in crashdump is fine.
OK, then comment about this at freeze_comm[] definition so that it's
clear it isn't just set-but-never-read field.
OK.
--- 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;
Why don't you just set the name in ioctl_fsfreeze() in both cases?
There are users of freeze_super() in GFS2 unless I'm misreading code.
Yes, there are. The call in fs/gfs2/glops.c is in a call path from
-freeze_super() handler for GFS2 so that one is handled in
ioctl_fsfreeze() anyway. The call in fs/gfs2/sys.c is a way to freeze
filesystem via sysfs (dunno why GFS2 has to invent its own thing and ioctl
isn't enough). Steven? So having the logic in ioctl_fsfreeze(),
freeze_bdev() and freeze_store() in gfs2 seems to be enough.
Jan, my logic is as follows.
Recording freezer task name is not filesystem/device specific and
thus should be done in generic code. So no changes in GFS2.
freeze_super() is generic counterpart to filesystem/device
specific -freeze_super() hook, look how they are paired.
It should recore freezer task name, so any future user
will not forget to do the same.
So it's in ioctl_fsfreeze(), freeze_bdev() and freeze_super().
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1221,6 +1221,8 @@ 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 */
+ charfreeze_comm[16];
Here should be TASK_COMM_LEN, shouldn't it?
It will pull sched.h, dunno if we care about headers anymore.
That's not ideal but IMHO better than having the value hardcoded here.
That is pretty fragile - i.e. think what happens when someone decides to
increase TASK_COMM_LEN...
TASK_COMM_LEN is userspace ABI via at least prctl(PR_SET_NAME).
I can formally move it to include/uapi/linux/sched.h.
This allows to not drag sched.h into fs.h for one tiny define.
Alexey
Re: [Cluster-devel] [PATCH] fs: record task name which froze superblock
On Fri 20-02-15 14:42:29, Alexey Dobriyan wrote:
On Wed, Feb 18, 2015 at 12:13 PM, Jan Kara j...@suse.cz wrote:
--- 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;
Why don't you just set the name in ioctl_fsfreeze() in both cases?
There are users of freeze_super() in GFS2 unless I'm misreading code.
Yes, there are. The call in fs/gfs2/glops.c is in a call path from
-freeze_super() handler for GFS2 so that one is handled in
ioctl_fsfreeze() anyway. The call in fs/gfs2/sys.c is a way to freeze
filesystem via sysfs (dunno why GFS2 has to invent its own thing and ioctl
isn't enough). Steven? So having the logic in ioctl_fsfreeze(),
freeze_bdev() and freeze_store() in gfs2 seems to be enough.
Jan, my logic is as follows.
Recording freezer task name is not filesystem/device specific and
thus should be done in generic code. So no changes in GFS2.
freeze_super() is generic counterpart to filesystem/device
specific -freeze_super() hook, look how they are paired.
It should recore freezer task name, so any future user
will not forget to do the same.
So it's in ioctl_fsfreeze(), freeze_bdev() and freeze_super().
Well, but this stores the name in two different levels - once in the top
level (ioctl_fsfreeze(), freeze_bdev()) and once in a place called from
there (freeze_super()). That just seems wrong to me. You can just record
the frozen process in freeze_super() and mandate that if someone manages to
freeze the fs without calling freeze_super() from his -freeze_super()
handler (currently there isn't such filesystem), he is also responsible for
setting freezer name... Hmm?
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1221,6 +1221,8 @@ 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 */
+ charfreeze_comm[16];
Here should be TASK_COMM_LEN, shouldn't it?
It will pull sched.h, dunno if we care about headers anymore.
That's not ideal but IMHO better than having the value hardcoded here.
That is pretty fragile - i.e. think what happens when someone decides to
increase TASK_COMM_LEN...
TASK_COMM_LEN is userspace ABI via at least prctl(PR_SET_NAME).
I can formally move it to include/uapi/linux/sched.h.
This allows to not drag sched.h into fs.h for one tiny define.
OK, moving the definition would be preferable to me (and IMO also a
cleanup).
Honza
--
Jan Kara j...@suse.cz
SUSE Labs, CR
Re: [Cluster-devel] [PATCH] fs: record task name which froze superblock
On Wed 18-02-15 10:34:55, Alexey Dobriyan wrote:
On Mon, Feb 16, 2015 at 10:38:52AM +0100, Jan Kara wrote:
On Sat 14-02-15 21:55:24, Alexey Dobriyan wrote:
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. Record at least task name (we can't take task_struct
reference) to make support engineer's life easier.
Hopefully 16 bytes per superblock isn't much.
P.S.: Cc'ing GFS2 people just in case they want to correct
my understanding of GFS2 having async freeze code.
Signed-off-by: Alexey Dobriyan adobri...@gmail.com
Hum, and when do you show the task name? Or do you expect that customer
takes a crashdump and support just finds it in memory?
Yeah, having at least something in crashdump is fine.
OK, then comment about this at freeze_comm[] definition so that it's
clear it isn't just set-but-never-read field.
--- 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;
Why don't you just set the name in ioctl_fsfreeze() in both cases?
There are users of freeze_super() in GFS2 unless I'm misreading code.
Yes, there are. The call in fs/gfs2/glops.c is in a call path from
-freeze_super() handler for GFS2 so that one is handled in
ioctl_fsfreeze() anyway. The call in fs/gfs2/sys.c is a way to freeze
filesystem via sysfs (dunno why GFS2 has to invent its own thing and ioctl
isn't enough). Steven? So having the logic in ioctl_fsfreeze(),
freeze_bdev() and freeze_store() in gfs2 seems to be enough.
Also you seem to be missing freezing / thawing in freeze/thaw_bdev()
functions.
You are correct. Resending patch (blockdev freezing tested with XFS).
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1221,6 +1221,8 @@ 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 */
+ charfreeze_comm[16];
Here should be TASK_COMM_LEN, shouldn't it?
It will pull sched.h, dunno if we care about headers anymore.
That's not ideal but IMHO better than having the value hardcoded here.
That is pretty fragile - i.e. think what happens when someone decides to
increase TASK_COMM_LEN...
Honza
--
Jan Kara j...@suse.cz
SUSE Labs, CR
Re: [Cluster-devel] [PATCH] fs: record task name which froze superblock
Hi,
On 18/02/15 09:13, Jan Kara wrote:
On Wed 18-02-15 10:34:55, Alexey Dobriyan wrote:
On Mon, Feb 16, 2015 at 10:38:52AM +0100, Jan Kara wrote:
On Sat 14-02-15 21:55:24, Alexey Dobriyan wrote:
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. Record at least task name (we can't take task_struct
reference) to make support engineer's life easier.
Hopefully 16 bytes per superblock isn't much.
P.S.: Cc'ing GFS2 people just in case they want to correct
my understanding of GFS2 having async freeze code.
Signed-off-by: Alexey Dobriyan adobri...@gmail.com
Hum, and when do you show the task name? Or do you expect that customer
takes a crashdump and support just finds it in memory?
Yeah, having at least something in crashdump is fine.
OK, then comment about this at freeze_comm[] definition so that it's
clear it isn't just set-but-never-read field.
--- 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;
Why don't you just set the name in ioctl_fsfreeze() in both cases?
There are users of freeze_super() in GFS2 unless I'm misreading code.
Yes, there are. The call in fs/gfs2/glops.c is in a call path from
-freeze_super() handler for GFS2 so that one is handled in
ioctl_fsfreeze() anyway. The call in fs/gfs2/sys.c is a way to freeze
filesystem via sysfs (dunno why GFS2 has to invent its own thing and ioctl
isn't enough). Steven? So having the logic in ioctl_fsfreeze(),
freeze_bdev() and freeze_store() in gfs2 seems to be enough.
The sysfs freeze thing is historical and strongly deprecated - I hope
that we may be able to remove it one day,
Steve.
Re: [Cluster-devel] [PATCH] fs: record task name which froze superblock
On Mon, Feb 16, 2015 at 10:38:52AM +0100, Jan Kara wrote:
On Sat 14-02-15 21:55:24, Alexey Dobriyan wrote:
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. Record at least task name (we can't take task_struct
reference) to make support engineer's life easier.
Hopefully 16 bytes per superblock isn't much.
P.S.: Cc'ing GFS2 people just in case they want to correct
my understanding of GFS2 having async freeze code.
Signed-off-by: Alexey Dobriyan adobri...@gmail.com
Hum, and when do you show the task name? Or do you expect that customer
takes a crashdump and support just finds it in memory?
Yeah, having at least something in crashdump is fine.
--- 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;
Why don't you just set the name in ioctl_fsfreeze() in both cases?
There are users of freeze_super() in GFS2 unless I'm misreading code.
Also you seem to be missing freezing / thawing in freeze/thaw_bdev()
functions.
You are correct. Resending patch (blockdev freezing tested with XFS).
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1221,6 +1221,8 @@ 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 */
+ charfreeze_comm[16];
Here should be TASK_COMM_LEN, shouldn't it?
It will pull sched.h, dunno if we care about headers anymore.
Alexey
Re: [Cluster-devel] [PATCH] fs: record task name which froze superblock
On Sat 14-02-15 21:55:24, Alexey Dobriyan wrote:
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. Record at least task name (we can't take task_struct
reference) to make support engineer's life easier.
Hopefully 16 bytes per superblock isn't much.
P.S.: Cc'ing GFS2 people just in case they want to correct
my understanding of GFS2 having async freeze code.
Signed-off-by: Alexey Dobriyan adobri...@gmail.com
Hum, and when do you show the task name? Or do you expect that customer
takes a crashdump and support just finds it in memory?
---
fs/ioctl.c | 22 --
fs/super.c |2 ++
include/linux/fs.h |2 ++
3 files changed, 20 insertions(+), 6 deletions(-)
--- 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;
Why don't you just set the name in ioctl_fsfreeze() in both cases?
Also you seem to be missing freezing / thawing in freeze/thaw_bdev()
functions.
}
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
@@ -1355,6 +1355,7 @@ 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;
}
@@ -1391,6 +1392,7 @@ 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
@@ -1221,6 +1221,8 @@ 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 */
+ charfreeze_comm[16];
Here should be TASK_COMM_LEN, shouldn't it?
Honza
--
Jan Kara j...@suse.cz
SUSE Labs, CR
