From: Yu Kuai <[email protected]>
Before this patch, the implementation is hacky and hard to understand:
1) md_seq_start set pos to 1;
2) md_seq_show found pos is 1, then print Personalities;
3) md_seq_next found pos is 1, then it update pos to the first mddev;
4) md_seq_show found pos is not 1 or 2, show mddev;
5) md_seq_next found pos is not 1 or 2, update pos to next mddev;
6) loop 4-5 until the last mddev, then md_seq_next update pos to 2;
7) md_seq_show found pos is 2, then print unused devices;
8) md_seq_next found pos is 2, stop;
This patch remove the magic value and use seq_list_start/next/stop()
directly, and move printing "Personalities" to md_seq_start(),
"unsed devices" to md_seq_stop():
1) md_seq_start print Personalities, and then set pos to first mddev;
2) md_seq_show show mddev;
3) md_seq_next update pos to next mddev;
4) loop 2-3 until the last mddev;
5) md_seq_stop print unsed devices;
Signed-off-by: Yu Kuai <[email protected]>
---
drivers/md/md.c | 100 +++++++++++-------------------------------------
1 file changed, 22 insertions(+), 78 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 73782cafad4e..0b83a406e797 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8213,105 +8213,46 @@ static int status_resync(struct seq_file *seq, struct mddev *mddev)
}
static void *md_seq_start(struct seq_file *seq, loff_t *pos)
+ __acquires(&all_mddevs_lock)
{
- struct list_head *tmp;
- loff_t l = *pos;
- struct mddev *mddev;
+ struct md_personality *pers;
- if (l == 0x10000) {
- ++*pos;
- return (void *)2;
- }
- if (l > 0x10000)
- return NULL;
- if (!l--)
- /* header */
- return (void*)1;
+ seq_puts(seq, "Personalities : ");
+ spin_lock(&pers_lock);
+ list_for_each_entry(pers, &pers_list, list)
+ seq_printf(seq, "[%s] ", pers->name);
+
+ spin_unlock(&pers_lock);
+ seq_puts(seq, "\n");
+ seq->poll_event = atomic_read(&md_event_count);
spin_lock(&all_mddevs_lock);
- list_for_each(tmp,&all_mddevs)
- if (!l--) {
- mddev = list_entry(tmp, struct mddev, all_mddevs);
- if (!mddev_get(mddev))
- continue;
- spin_unlock(&all_mddevs_lock);
- return mddev;
- }
- spin_unlock(&all_mddevs_lock);
- if (!l--)
- return (void*)2;/* tail */
- return NULL;
+
+ return seq_list_start(&all_mddevs, *pos);
}
static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
- struct list_head *tmp;
- struct mddev *next_mddev, *mddev = v;
- struct mddev *to_put = NULL;
-
- ++*pos;
- if (v == (void*)2)
- return NULL;
-
- spin_lock(&all_mddevs_lock);
- if (v == (void*)1) {
- tmp = all_mddevs.next;
- } else {
- to_put = mddev;
- tmp = mddev->all_mddevs.next;
- }
-
- for (;;) {
- if (tmp == &all_mddevs) {
- next_mddev = (void*)2;
- *pos = 0x10000;
- break;
- }
- next_mddev = list_entry(tmp, struct mddev, all_mddevs);
- if (mddev_get(next_mddev))
- break;
- mddev = next_mddev;
- tmp = mddev->all_mddevs.next;
- }
- spin_unlock(&all_mddevs_lock);
-
- if (to_put)
- mddev_put(to_put);
- return next_mddev;
-
+ return seq_list_next(v, &all_mddevs, pos);
}
static void md_seq_stop(struct seq_file *seq, void *v)
+ __releases(&all_mddevs_lock)
{
- struct mddev *mddev = v;
-
- if (mddev && v != (void*)1 && v != (void*)2)
- mddev_put(mddev);
+ status_unused(seq);
+ spin_unlock(&all_mddevs_lock);
}
static int md_seq_show(struct seq_file *seq, void *v)
{
- struct mddev *mddev = v;
+ struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
sector_t sectors;
struct md_rdev *rdev;
- if (v == (void*)1) {
- struct md_personality *pers;
- seq_printf(seq, "Personalities : ");
- spin_lock(&pers_lock);
- list_for_each_entry(pers, &pers_list, list)
- seq_printf(seq, "[%s] ", pers->name);
-
- spin_unlock(&pers_lock);
- seq_printf(seq, "\n");
- seq->poll_event = atomic_read(&md_event_count);
+ if (!mddev_get(mddev))
return 0;
- }
- if (v == (void*)2) {
- status_unused(seq);
- return 0;
- }
+ spin_unlock(&all_mddevs_lock);
spin_lock(&mddev->lock);
if (mddev->pers || mddev->raid_disks || !list_empty(&mddev->disks)) {
seq_printf(seq, "%s : %sactive", mdname(mddev),
@@ -8382,6 +8323,9 @@ static int md_seq_show(struct seq_file *seq, void *v)
seq_printf(seq, "\n");
}
spin_unlock(&mddev->lock);
+ spin_lock(&all_mddevs_lock);
+ if (atomic_dec_and_test(&mddev->active))
+ __mddev_put(mddev);
return 0;
}
--
2.39.2
On Tue, Sep 26, 2023 at 11:19 PM Yu Kuai <[email protected]> wrote:
>
> From: Yu Kuai <[email protected]>
>
> Before this patch, the implementation is hacky and hard to understand:
>
> 1) md_seq_start set pos to 1;
> 2) md_seq_show found pos is 1, then print Personalities;
> 3) md_seq_next found pos is 1, then it update pos to the first mddev;
> 4) md_seq_show found pos is not 1 or 2, show mddev;
> 5) md_seq_next found pos is not 1 or 2, update pos to next mddev;
> 6) loop 4-5 until the last mddev, then md_seq_next update pos to 2;
> 7) md_seq_show found pos is 2, then print unused devices;
> 8) md_seq_next found pos is 2, stop;
>
> This patch remove the magic value and use seq_list_start/next/stop()
> directly, and move printing "Personalities" to md_seq_start(),
> "unsed devices" to md_seq_stop():
>
> 1) md_seq_start print Personalities, and then set pos to first mddev;
> 2) md_seq_show show mddev;
> 3) md_seq_next update pos to next mddev;
> 4) loop 2-3 until the last mddev;
> 5) md_seq_stop print unsed devices;
>
> Signed-off-by: Yu Kuai <[email protected]>
Just realized this introduced a behavior change:
When there is not md devices, before this patch, we have
[root@eth50-1 ~]# cat /proc/mdstat
Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
unused devices: <none>
After this patch, "cat /proc/mdstat" returns nothing. This causes
some confusion for users who want to read "Personalities" line,
for example, the mdadm test suite reads it.
I haven't figured out the best fix yet.
Thanks,
Song
Hi,
在 2024/01/09 7:38, Song Liu 写道:
> On Tue, Sep 26, 2023 at 11:19 PM Yu Kuai <[email protected]> wrote:
>>
>> From: Yu Kuai <[email protected]>
>>
>> Before this patch, the implementation is hacky and hard to understand:
>>
>> 1) md_seq_start set pos to 1;
>> 2) md_seq_show found pos is 1, then print Personalities;
>> 3) md_seq_next found pos is 1, then it update pos to the first mddev;
>> 4) md_seq_show found pos is not 1 or 2, show mddev;
>> 5) md_seq_next found pos is not 1 or 2, update pos to next mddev;
>> 6) loop 4-5 until the last mddev, then md_seq_next update pos to 2;
>> 7) md_seq_show found pos is 2, then print unused devices;
>> 8) md_seq_next found pos is 2, stop;
>>
>> This patch remove the magic value and use seq_list_start/next/stop()
>> directly, and move printing "Personalities" to md_seq_start(),
>> "unsed devices" to md_seq_stop():
>>
>> 1) md_seq_start print Personalities, and then set pos to first mddev;
>> 2) md_seq_show show mddev;
>> 3) md_seq_next update pos to next mddev;
>> 4) loop 2-3 until the last mddev;
>> 5) md_seq_stop print unsed devices;
>>
>> Signed-off-by: Yu Kuai <[email protected]>
>
> Just realized this introduced a behavior change:
>
> When there is not md devices, before this patch, we have
>
> [root@eth50-1 ~]# cat /proc/mdstat
> Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
> unused devices: <none>
>
> After this patch, "cat /proc/mdstat" returns nothing. This causes
> some confusion for users who want to read "Personalities" line,
> for example, the mdadm test suite reads it.
>
> I haven't figured out the best fix yet.
Yes, that's a problem. And after reviewing seq_read_iter() in detail, I
realize that I also can't use seq_printf() in m->op->start() directly,
because if seq buffer overflowed, md_seq_start() can be called more than
once.
I'll fix these problems soon.
Thanks,
Kuai
>
> Thanks,
> Song
>
> .
>
Hi,
在 2024/01/09 9:21, Yu Kuai 写道:
> Hi,
>
> 在 2024/01/09 7:38, Song Liu 写道:
>> On Tue, Sep 26, 2023 at 11:19 PM Yu Kuai <[email protected]> wrote:
>>>
>>> From: Yu Kuai <[email protected]>
>>>
>>> Before this patch, the implementation is hacky and hard to understand:
>>>
>>> 1) md_seq_start set pos to 1;
>>> 2) md_seq_show found pos is 1, then print Personalities;
>>> 3) md_seq_next found pos is 1, then it update pos to the first mddev;
>>> 4) md_seq_show found pos is not 1 or 2, show mddev;
>>> 5) md_seq_next found pos is not 1 or 2, update pos to next mddev;
>>> 6) loop 4-5 until the last mddev, then md_seq_next update pos to 2;
>>> 7) md_seq_show found pos is 2, then print unused devices;
>>> 8) md_seq_next found pos is 2, stop;
>>>
>>> This patch remove the magic value and use seq_list_start/next/stop()
>>> directly, and move printing "Personalities" to md_seq_start(),
>>> "unsed devices" to md_seq_stop():
>>>
>>> 1) md_seq_start print Personalities, and then set pos to first mddev;
>>> 2) md_seq_show show mddev;
>>> 3) md_seq_next update pos to next mddev;
>>> 4) loop 2-3 until the last mddev;
>>> 5) md_seq_stop print unsed devices;
>>>
>>> Signed-off-by: Yu Kuai <[email protected]>
>>
>> Just realized this introduced a behavior change:
>>
>> When there is not md devices, before this patch, we have
>>
>> [root@eth50-1 ~]# cat /proc/mdstat
>> Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
>> unused devices: <none>
>>
>> After this patch, "cat /proc/mdstat" returns nothing. This causes
>> some confusion for users who want to read "Personalities" line,
>> for example, the mdadm test suite reads it.
>>
>> I haven't figured out the best fix yet.
>
> Yes, that's a problem. And after reviewing seq_read_iter() in detail, I
> realize that I also can't use seq_printf() in m->op->start() directly,
> because if seq buffer overflowed, md_seq_start() can be called more than
> once.
>
> I'll fix these problems soon.
How about following patch(already tested)?
Thanks,
Kuai
diff --git a/drivers/md/md.c b/drivers/md/md.c
index e351e6c51cc7..289d3d89e73d 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8135,6 +8135,19 @@ static void status_unused(struct seq_file *seq)
seq_printf(seq, "\n");
}
+static void status_personalities(struct seq_file *seq)
+{
+ struct md_personality *pers;
+
+ seq_puts(seq, "Personalities : ");
+ spin_lock(&pers_lock);
+ list_for_each_entry(pers, &pers_list, list)
+ seq_printf(seq, "[%s] ", pers->name);
+
+ spin_unlock(&pers_lock);
+ seq_puts(seq, "\n");
+}
+
static int status_resync(struct seq_file *seq, struct mddev *mddev)
{
sector_t max_sectors, resync, res;
@@ -8273,43 +8286,53 @@ static int status_resync(struct seq_file *seq,
struct mddev *mddev)
return 1;
}
+#define MDDEV_NONE (void *)1
+
static void *md_seq_start(struct seq_file *seq, loff_t *pos)
__acquires(&all_mddevs_lock)
{
- struct md_personality *pers;
-
- seq_puts(seq, "Personalities : ");
- spin_lock(&pers_lock);
- list_for_each_entry(pers, &pers_list, list)
- seq_printf(seq, "[%s] ", pers->name);
-
- spin_unlock(&pers_lock);
- seq_puts(seq, "\n");
seq->poll_event = atomic_read(&md_event_count);
-
spin_lock(&all_mddevs_lock);
- return seq_list_start(&all_mddevs, *pos);
+ if (!list_empty(&all_mddevs))
+ return seq_list_start(&all_mddevs, *pos);
+ else if (*pos == 0)
+ return MDDEV_NONE;
+ else
+ return NULL;
}
static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
+ if (v == MDDEV_NONE) {
+ ++*pos;
+ return NULL;
+ }
+
return seq_list_next(v, &all_mddevs, pos);
}
static void md_seq_stop(struct seq_file *seq, void *v)
__releases(&all_mddevs_lock)
{
- status_unused(seq);
spin_unlock(&all_mddevs_lock);
}
static int md_seq_show(struct seq_file *seq, void *v)
{
- struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
+ struct mddev *mddev;
sector_t sectors;
struct md_rdev *rdev;
+ if (v == MDDEV_NONE) {
+ status_personalities(seq);
+ status_unused(seq);
+ return 0;
+ }
+
+ mddev = list_entry(v, struct mddev, all_mddevs);
+ if (mddev == list_first_entry(&all_mddevs, struct mddev,
all_mddevs))
+ status_personalities(seq);
if (!mddev_get(mddev))
return 0;
@@ -8385,6 +8408,10 @@ static int md_seq_show(struct seq_file *seq, void *v)
}
spin_unlock(&mddev->lock);
spin_lock(&all_mddevs_lock);
+
+ if (mddev == list_last_entry(&all_mddevs, struct mddev, all_mddevs))
+ status_unused(seq);
+
if (atomic_dec_and_test(&mddev->active))
__mddev_put(mddev);
>
> Thanks,
> Kuai
>
>>
>> Thanks,
>> Song
>>
>> .
>>
>
> .
>
On Mon, Jan 8, 2024 at 11:48 PM Yu Kuai <[email protected]> wrote:
>
> Hi,
>
> 在 2024/01/09 9:21, Yu Kuai 写道:
> > Hi,
> >
> > 在 2024/01/09 7:38, Song Liu 写道:
> >> On Tue, Sep 26, 2023 at 11:19 PM Yu Kuai <[email protected]> wrote:
[...]
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index e351e6c51cc7..289d3d89e73d 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8135,6 +8135,19 @@ static void status_unused(struct seq_file *seq)
> seq_printf(seq, "\n");
> }
>
> +static void status_personalities(struct seq_file *seq)
> +{
> + struct md_personality *pers;
> +
> + seq_puts(seq, "Personalities : ");
> + spin_lock(&pers_lock);
> + list_for_each_entry(pers, &pers_list, list)
> + seq_printf(seq, "[%s] ", pers->name);
> +
> + spin_unlock(&pers_lock);
> + seq_puts(seq, "\n");
> +}
> +
> static int status_resync(struct seq_file *seq, struct mddev *mddev)
> {
> sector_t max_sectors, resync, res;
> @@ -8273,43 +8286,53 @@ static int status_resync(struct seq_file *seq,
> struct mddev *mddev)
> return 1;
> }
>
> +#define MDDEV_NONE (void *)1
> +
> static void *md_seq_start(struct seq_file *seq, loff_t *pos)
> __acquires(&all_mddevs_lock)
> {
> - struct md_personality *pers;
> -
> - seq_puts(seq, "Personalities : ");
> - spin_lock(&pers_lock);
> - list_for_each_entry(pers, &pers_list, list)
> - seq_printf(seq, "[%s] ", pers->name);
> -
> - spin_unlock(&pers_lock);
> - seq_puts(seq, "\n");
> seq->poll_event = atomic_read(&md_event_count);
> -
> spin_lock(&all_mddevs_lock);
>
> - return seq_list_start(&all_mddevs, *pos);
> + if (!list_empty(&all_mddevs))
> + return seq_list_start(&all_mddevs, *pos);
> + else if (*pos == 0)
> + return MDDEV_NONE;
> + else
> + return NULL;
> }
>
> static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> {
> + if (v == MDDEV_NONE) {
> + ++*pos;
> + return NULL;
> + }
> +
> return seq_list_next(v, &all_mddevs, pos);
> }
>
> static void md_seq_stop(struct seq_file *seq, void *v)
> __releases(&all_mddevs_lock)
> {
> - status_unused(seq);
> spin_unlock(&all_mddevs_lock);
> }
> static int md_seq_show(struct seq_file *seq, void *v)
> {
> - struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
> + struct mddev *mddev;
> sector_t sectors;
> struct md_rdev *rdev;
>
> + if (v == MDDEV_NONE) {
> + status_personalities(seq);
> + status_unused(seq);
> + return 0;
> + }
> +
> + mddev = list_entry(v, struct mddev, all_mddevs);
> + if (mddev == list_first_entry(&all_mddevs, struct mddev,
> all_mddevs))
> + status_personalities(seq);
> if (!mddev_get(mddev))
> return 0;
>
> @@ -8385,6 +8408,10 @@ static int md_seq_show(struct seq_file *seq, void *v)
> }
> spin_unlock(&mddev->lock);
> spin_lock(&all_mddevs_lock);
> +
> + if (mddev == list_last_entry(&all_mddevs, struct mddev, all_mddevs))
> + status_unused(seq);
> +
> if (atomic_dec_and_test(&mddev->active))
> __mddev_put(mddev);
>
I think something like the following is the right way to do this.
Thanks,
Song
diff --git i/drivers/md/md.c w/drivers/md/md.c
index 38a6767c65b1..14044febe009 100644
--- i/drivers/md/md.c
+++ w/drivers/md/md.c
@@ -8215,20 +8215,8 @@ static int status_resync(struct seq_file *seq,
struct mddev *mddev)
static void *md_seq_start(struct seq_file *seq, loff_t *pos)
__acquires(&all_mddevs_lock)
{
- struct md_personality *pers;
-
- seq_puts(seq, "Personalities : ");
- spin_lock(&pers_lock);
- list_for_each_entry(pers, &pers_list, list)
- seq_printf(seq, "[%s] ", pers->name);
-
- spin_unlock(&pers_lock);
- seq_puts(seq, "\n");
- seq->poll_event = atomic_read(&md_event_count);
-
spin_lock(&all_mddevs_lock);
-
- return seq_list_start(&all_mddevs, *pos);
+ return seq_list_start_head(&all_mddevs, *pos);
}
static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
@@ -8243,12 +8231,31 @@ static void md_seq_stop(struct seq_file *seq, void *v)
spin_unlock(&all_mddevs_lock);
}
+static void md_seq_print_header(struct seq_file *seq)
+{
+ struct md_personality *pers;
+
+ seq_puts(seq, "Personalities : ");
+ spin_lock(&pers_lock);
+ list_for_each_entry(pers, &pers_list, list)
+ seq_printf(seq, "[%s] ", pers->name);
+
+ spin_unlock(&pers_lock);
+ seq_puts(seq, "\n");
+ seq->poll_event = atomic_read(&md_event_count);
+}
+
static int md_seq_show(struct seq_file *seq, void *v)
{
struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
sector_t sectors;
struct md_rdev *rdev;
+ if (v == &all_mddevs) {
+ md_seq_print_header(seq);
+ return 0;
+ }
+
if (!mddev_get(mddev))
return 0;
Hi,
在 2024/01/09 16:12, Song Liu 写道:
> On Mon, Jan 8, 2024 at 11:48 PM Yu Kuai <[email protected]> wrote:
>>
>> Hi,
>>
>> 在 2024/01/09 9:21, Yu Kuai 写道:
>>> Hi,
>>>
>>> 在 2024/01/09 7:38, Song Liu 写道:
>>>> On Tue, Sep 26, 2023 at 11:19 PM Yu Kuai <[email protected]> wrote:
> [...]
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index e351e6c51cc7..289d3d89e73d 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -8135,6 +8135,19 @@ static void status_unused(struct seq_file *seq)
>> seq_printf(seq, "\n");
>> }
>>
>> +static void status_personalities(struct seq_file *seq)
>> +{
>> + struct md_personality *pers;
>> +
>> + seq_puts(seq, "Personalities : ");
>> + spin_lock(&pers_lock);
>> + list_for_each_entry(pers, &pers_list, list)
>> + seq_printf(seq, "[%s] ", pers->name);
>> +
>> + spin_unlock(&pers_lock);
>> + seq_puts(seq, "\n");
>> +}
>> +
>> static int status_resync(struct seq_file *seq, struct mddev *mddev)
>> {
>> sector_t max_sectors, resync, res;
>> @@ -8273,43 +8286,53 @@ static int status_resync(struct seq_file *seq,
>> struct mddev *mddev)
>> return 1;
>> }
>>
>> +#define MDDEV_NONE (void *)1
>> +
>> static void *md_seq_start(struct seq_file *seq, loff_t *pos)
>> __acquires(&all_mddevs_lock)
>> {
>> - struct md_personality *pers;
>> -
>> - seq_puts(seq, "Personalities : ");
>> - spin_lock(&pers_lock);
>> - list_for_each_entry(pers, &pers_list, list)
>> - seq_printf(seq, "[%s] ", pers->name);
>> -
>> - spin_unlock(&pers_lock);
>> - seq_puts(seq, "\n");
>> seq->poll_event = atomic_read(&md_event_count);
>> -
>> spin_lock(&all_mddevs_lock);
>>
>> - return seq_list_start(&all_mddevs, *pos);
>> + if (!list_empty(&all_mddevs))
>> + return seq_list_start(&all_mddevs, *pos);
>> + else if (*pos == 0)
>> + return MDDEV_NONE;
>> + else
>> + return NULL;
>> }
>>
>> static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
>> {
>> + if (v == MDDEV_NONE) {
>> + ++*pos;
>> + return NULL;
>> + }
>> +
>> return seq_list_next(v, &all_mddevs, pos);
>> }
>>
>> static void md_seq_stop(struct seq_file *seq, void *v)
>> __releases(&all_mddevs_lock)
>> {
>> - status_unused(seq);
>> spin_unlock(&all_mddevs_lock);
>> }
>> static int md_seq_show(struct seq_file *seq, void *v)
>> {
>> - struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
>> + struct mddev *mddev;
>> sector_t sectors;
>> struct md_rdev *rdev;
>>
>> + if (v == MDDEV_NONE) {
>> + status_personalities(seq);
>> + status_unused(seq);
>> + return 0;
>> + }
>> +
>> + mddev = list_entry(v, struct mddev, all_mddevs);
>> + if (mddev == list_first_entry(&all_mddevs, struct mddev,
>> all_mddevs))
>> + status_personalities(seq);
>> if (!mddev_get(mddev))
>> return 0;
>>
>> @@ -8385,6 +8408,10 @@ static int md_seq_show(struct seq_file *seq, void *v)
>> }
>> spin_unlock(&mddev->lock);
>> spin_lock(&all_mddevs_lock);
>> +
>> + if (mddev == list_last_entry(&all_mddevs, struct mddev, all_mddevs))
>> + status_unused(seq);
>> +
>> if (atomic_dec_and_test(&mddev->active))
>> __mddev_put(mddev);
>>
>
> I think something like the following is the right way to do this.
>
> Thanks,
> Song
>
> diff --git i/drivers/md/md.c w/drivers/md/md.c
> index 38a6767c65b1..14044febe009 100644
> --- i/drivers/md/md.c
> +++ w/drivers/md/md.c
> @@ -8215,20 +8215,8 @@ static int status_resync(struct seq_file *seq,
> struct mddev *mddev)
> static void *md_seq_start(struct seq_file *seq, loff_t *pos)
> __acquires(&all_mddevs_lock)
> {
> - struct md_personality *pers;
> -
> - seq_puts(seq, "Personalities : ");
> - spin_lock(&pers_lock);
> - list_for_each_entry(pers, &pers_list, list)
> - seq_printf(seq, "[%s] ", pers->name);
> -
> - spin_unlock(&pers_lock);
> - seq_puts(seq, "\n");
> - seq->poll_event = atomic_read(&md_event_count);
> -
> spin_lock(&all_mddevs_lock);
> -
> - return seq_list_start(&all_mddevs, *pos);
> + return seq_list_start_head(&all_mddevs, *pos);
Yes, this is good. I didn't notice the api seq_list_start_head().
> }
>
> static void *md_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> @@ -8243,12 +8231,31 @@ static void md_seq_stop(struct seq_file *seq, void *v)
> spin_unlock(&all_mddevs_lock);
> }
>
> +static void md_seq_print_header(struct seq_file *seq)
> +{
> + struct md_personality *pers;
> +
> + seq_puts(seq, "Personalities : ");
> + spin_lock(&pers_lock);
> + list_for_each_entry(pers, &pers_list, list)
> + seq_printf(seq, "[%s] ", pers->name);
> +
> + spin_unlock(&pers_lock);
> + seq_puts(seq, "\n");
> + seq->poll_event = atomic_read(&md_event_count);
> +}
> +
> static int md_seq_show(struct seq_file *seq, void *v)
> {
> struct mddev *mddev = list_entry(v, struct mddev, all_mddevs);
> sector_t sectors;
> struct md_rdev *rdev;
>
> + if (v == &all_mddevs) {
> + md_seq_print_header(seq);
And I will still move status_unused() to md_seq_show(), because
seq_read_iter() only handle the case that seq_printf() overflowed from
md_seq_show(), not md_seq_start/stop().
Thanks,
Kuai
> + return 0;
> + }
> +
> if (!mddev_get(mddev))
> return 0;
>
> .
>