Re: [f2fs-dev] [PATCH] f2fs: do not use mutex lock in atomic context
On 2/15/2019 2:40 PM, Chao Yu wrote: On 2019/2/15 12:28, Ritesh Harjani wrote: On 2/14/2019 9:40 PM, Chao Yu wrote: On 2019-2-14 15:46, Sahitya Tummala wrote: On Wed, Feb 13, 2019 at 11:25:31AM +0800, Chao Yu wrote: On 2019/2/4 16:06, Sahitya Tummala wrote: Fix below warning coming because of using mutex lock in atomic context. BUG: sleeping function called from invalid context at kernel/locking/mutex.c:98 in_atomic(): 1, irqs_disabled(): 0, pid: 585, name: sh Preemption disabled at: __radix_tree_preload+0x28/0x130 Call trace: dump_backtrace+0x0/0x2b4 show_stack+0x20/0x28 dump_stack+0xa8/0xe0 ___might_sleep+0x144/0x194 __might_sleep+0x58/0x8c mutex_lock+0x2c/0x48 f2fs_trace_pid+0x88/0x14c f2fs_set_node_page_dirty+0xd0/0x184 Do not use f2fs_radix_tree_insert() to avoid doing cond_resched() with spin_lock() acquired. Signed-off-by: Sahitya Tummala --- fs/f2fs/trace.c | 20 +--- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/fs/f2fs/trace.c b/fs/f2fs/trace.c index ce2a5eb..d0ab533 100644 --- a/fs/f2fs/trace.c +++ b/fs/f2fs/trace.c @@ -14,7 +14,7 @@ #include "trace.h" static RADIX_TREE(pids, GFP_ATOMIC); -static struct mutex pids_lock; +static spinlock_t pids_lock; static struct last_io_info last_io; static inline void __print_last_io(void) @@ -58,23 +58,29 @@ void f2fs_trace_pid(struct page *page) set_page_private(page, (unsigned long)pid); +retry: if (radix_tree_preload(GFP_NOFS)) return; - mutex_lock(_lock); + spin_lock(_lock); p = radix_tree_lookup(, pid); if (p == current) goto out; if (p) radix_tree_delete(, pid); - f2fs_radix_tree_insert(, pid, current); Do you know why do we have a retry logic here? When anyways we have called for radix_tree_delete with pid key? Which should ensure the slot is empty, no? Then why in the original code (f2fs_radix_tree_insert), we were retrying. For what condition a retry was needed? Hi, f2fs_radix_tree_insert is used in many places, it was introduced to used in some paths we should not failed. And here, I guess we used it for the same purpose, if we failed to insert @current pointer into radix, next time, we may not skip calling trace_printk, actually it will print the same current->comm info as previous one, it's redundant. Sure, thanks for the info. Regards Ritesh
Re: [f2fs-dev] [PATCH] f2fs: do not use mutex lock in atomic context
On 2019/2/15 12:28, Ritesh Harjani wrote:
>
> On 2/14/2019 9:40 PM, Chao Yu wrote:
>> On 2019-2-14 15:46, Sahitya Tummala wrote:
>>> On Wed, Feb 13, 2019 at 11:25:31AM +0800, Chao Yu wrote:
On 2019/2/4 16:06, Sahitya Tummala wrote:
> Fix below warning coming because of using mutex lock in atomic context.
>
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:98
> in_atomic(): 1, irqs_disabled(): 0, pid: 585, name: sh
> Preemption disabled at: __radix_tree_preload+0x28/0x130
> Call trace:
> dump_backtrace+0x0/0x2b4
> show_stack+0x20/0x28
> dump_stack+0xa8/0xe0
> ___might_sleep+0x144/0x194
> __might_sleep+0x58/0x8c
> mutex_lock+0x2c/0x48
> f2fs_trace_pid+0x88/0x14c
> f2fs_set_node_page_dirty+0xd0/0x184
>
> Do not use f2fs_radix_tree_insert() to avoid doing cond_resched() with
> spin_lock() acquired.
>
> Signed-off-by: Sahitya Tummala
> ---
> fs/f2fs/trace.c | 20 +---
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/fs/f2fs/trace.c b/fs/f2fs/trace.c
> index ce2a5eb..d0ab533 100644
> --- a/fs/f2fs/trace.c
> +++ b/fs/f2fs/trace.c
> @@ -14,7 +14,7 @@
> #include "trace.h"
>
> static RADIX_TREE(pids, GFP_ATOMIC);
> -static struct mutex pids_lock;
> +static spinlock_t pids_lock;
> static struct last_io_info last_io;
>
> static inline void __print_last_io(void)
> @@ -58,23 +58,29 @@ void f2fs_trace_pid(struct page *page)
>
> set_page_private(page, (unsigned long)pid);
>
> +retry:
> if (radix_tree_preload(GFP_NOFS))
> return;
>
> - mutex_lock(_lock);
> + spin_lock(_lock);
> p = radix_tree_lookup(, pid);
> if (p == current)
> goto out;
> if (p)
> radix_tree_delete(, pid);
>
> - f2fs_radix_tree_insert(, pid, current);
>
> Do you know why do we have a retry logic here? When anyways we have
> called for radix_tree_delete with pid key?
> Which should ensure the slot is empty, no?
> Then why in the original code (f2fs_radix_tree_insert), we were
> retrying. For what condition a retry was needed?
Hi,
f2fs_radix_tree_insert is used in many places, it was introduced to used in
some paths we should not failed.
And here, I guess we used it for the same purpose, if we failed to insert
@current pointer into radix, next time, we may not skip calling
trace_printk, actually it will print the same current->comm info as
previous one, it's redundant.
Thanks,
>
> Regards
> Ritesh
>
>
> + if (radix_tree_insert(, pid, current)) {
> + spin_unlock(_lock);
> + radix_tree_preload_end();
> + cond_resched();
> + goto retry;
> + }
>
> trace_printk("%3x:%3x %4x %-16s\n",
> MAJOR(inode->i_sb->s_dev),
> MINOR(inode->i_sb->s_dev),
> pid, current->comm);
Hi Sahitya,
Can trace_printk sleep? For safety, how about moving it out of spinlock?
>>> Hi Chao,
>>>
>>> Yes, trace_printk() is safe to use in atomic context (unlike printk).
>> Hi Sahitya,
>>
>> Thanks for your confirmation. :)
>>
>> Reviewed-by: Chao Yu
>>
>> Thanks,
>>
>>> Thanks,
>>> Sahitya.
>>>
Thanks,
> out:
> - mutex_unlock(_lock);
> + spin_unlock(_lock);
> radix_tree_preload_end();
> }
>
> @@ -119,7 +125,7 @@ void f2fs_trace_ios(struct f2fs_io_info *fio, int
> flush)
>
> void f2fs_build_trace_ios(void)
> {
> - mutex_init(_lock);
> + spin_lock_init(_lock);
> }
>
> #define PIDVEC_SIZE 128
> @@ -147,7 +153,7 @@ void f2fs_destroy_trace_ios(void)
> pid_t next_pid = 0;
> unsigned int found;
>
> - mutex_lock(_lock);
> + spin_lock(_lock);
> while ((found = gang_lookup_pids(pid, next_pid, PIDVEC_SIZE))) {
> unsigned idx;
>
> @@ -155,5 +161,5 @@ void f2fs_destroy_trace_ios(void)
> for (idx = 0; idx < found; idx++)
> radix_tree_delete(, pid[idx]);
> }
> - mutex_unlock(_lock);
> + spin_unlock(_lock);
> }
>
>>
>> ___
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>> linux-f2fs-de...@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
> .
>
Re: [f2fs-dev] [PATCH] f2fs: do not use mutex lock in atomic context
On 2/14/2019 9:40 PM, Chao Yu wrote:
On 2019-2-14 15:46, Sahitya Tummala wrote:
On Wed, Feb 13, 2019 at 11:25:31AM +0800, Chao Yu wrote:
On 2019/2/4 16:06, Sahitya Tummala wrote:
Fix below warning coming because of using mutex lock in atomic context.
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:98
in_atomic(): 1, irqs_disabled(): 0, pid: 585, name: sh
Preemption disabled at: __radix_tree_preload+0x28/0x130
Call trace:
dump_backtrace+0x0/0x2b4
show_stack+0x20/0x28
dump_stack+0xa8/0xe0
___might_sleep+0x144/0x194
__might_sleep+0x58/0x8c
mutex_lock+0x2c/0x48
f2fs_trace_pid+0x88/0x14c
f2fs_set_node_page_dirty+0xd0/0x184
Do not use f2fs_radix_tree_insert() to avoid doing cond_resched() with
spin_lock() acquired.
Signed-off-by: Sahitya Tummala
---
fs/f2fs/trace.c | 20 +---
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/fs/f2fs/trace.c b/fs/f2fs/trace.c
index ce2a5eb..d0ab533 100644
--- a/fs/f2fs/trace.c
+++ b/fs/f2fs/trace.c
@@ -14,7 +14,7 @@
#include "trace.h"
static RADIX_TREE(pids, GFP_ATOMIC);
-static struct mutex pids_lock;
+static spinlock_t pids_lock;
static struct last_io_info last_io;
static inline void __print_last_io(void)
@@ -58,23 +58,29 @@ void f2fs_trace_pid(struct page *page)
set_page_private(page, (unsigned long)pid);
+retry:
if (radix_tree_preload(GFP_NOFS))
return;
- mutex_lock(_lock);
+ spin_lock(_lock);
p = radix_tree_lookup(, pid);
if (p == current)
goto out;
if (p)
radix_tree_delete(, pid);
- f2fs_radix_tree_insert(, pid, current);
Do you know why do we have a retry logic here? When anyways we have
called for radix_tree_delete with pid key?
Which should ensure the slot is empty, no?
Then why in the original code (f2fs_radix_tree_insert), we were
retrying. For what condition a retry was needed?
Regards
Ritesh
+ if (radix_tree_insert(, pid, current)) {
+ spin_unlock(_lock);
+ radix_tree_preload_end();
+ cond_resched();
+ goto retry;
+ }
trace_printk("%3x:%3x %4x %-16s\n",
MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
pid, current->comm);
Hi Sahitya,
Can trace_printk sleep? For safety, how about moving it out of spinlock?
Hi Chao,
Yes, trace_printk() is safe to use in atomic context (unlike printk).
Hi Sahitya,
Thanks for your confirmation. :)
Reviewed-by: Chao Yu
Thanks,
Thanks,
Sahitya.
Thanks,
out:
- mutex_unlock(_lock);
+ spin_unlock(_lock);
radix_tree_preload_end();
}
@@ -119,7 +125,7 @@ void f2fs_trace_ios(struct f2fs_io_info *fio, int flush)
void f2fs_build_trace_ios(void)
{
- mutex_init(_lock);
+ spin_lock_init(_lock);
}
#define PIDVEC_SIZE 128
@@ -147,7 +153,7 @@ void f2fs_destroy_trace_ios(void)
pid_t next_pid = 0;
unsigned int found;
- mutex_lock(_lock);
+ spin_lock(_lock);
while ((found = gang_lookup_pids(pid, next_pid, PIDVEC_SIZE))) {
unsigned idx;
@@ -155,5 +161,5 @@ void f2fs_destroy_trace_ios(void)
for (idx = 0; idx < found; idx++)
radix_tree_delete(, pid[idx]);
}
- mutex_unlock(_lock);
+ spin_unlock(_lock);
}
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Re: [f2fs-dev] [PATCH] f2fs: do not use mutex lock in atomic context
On 2019-2-14 15:46, Sahitya Tummala wrote:
> On Wed, Feb 13, 2019 at 11:25:31AM +0800, Chao Yu wrote:
>> On 2019/2/4 16:06, Sahitya Tummala wrote:
>>> Fix below warning coming because of using mutex lock in atomic context.
>>>
>>> BUG: sleeping function called from invalid context at
>>> kernel/locking/mutex.c:98
>>> in_atomic(): 1, irqs_disabled(): 0, pid: 585, name: sh
>>> Preemption disabled at: __radix_tree_preload+0x28/0x130
>>> Call trace:
>>> dump_backtrace+0x0/0x2b4
>>> show_stack+0x20/0x28
>>> dump_stack+0xa8/0xe0
>>> ___might_sleep+0x144/0x194
>>> __might_sleep+0x58/0x8c
>>> mutex_lock+0x2c/0x48
>>> f2fs_trace_pid+0x88/0x14c
>>> f2fs_set_node_page_dirty+0xd0/0x184
>>>
>>> Do not use f2fs_radix_tree_insert() to avoid doing cond_resched() with
>>> spin_lock() acquired.
>>>
>>> Signed-off-by: Sahitya Tummala
>>> ---
>>> fs/f2fs/trace.c | 20 +---
>>> 1 file changed, 13 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/fs/f2fs/trace.c b/fs/f2fs/trace.c
>>> index ce2a5eb..d0ab533 100644
>>> --- a/fs/f2fs/trace.c
>>> +++ b/fs/f2fs/trace.c
>>> @@ -14,7 +14,7 @@
>>> #include "trace.h"
>>>
>>> static RADIX_TREE(pids, GFP_ATOMIC);
>>> -static struct mutex pids_lock;
>>> +static spinlock_t pids_lock;
>>> static struct last_io_info last_io;
>>>
>>> static inline void __print_last_io(void)
>>> @@ -58,23 +58,29 @@ void f2fs_trace_pid(struct page *page)
>>>
>>> set_page_private(page, (unsigned long)pid);
>>>
>>> +retry:
>>> if (radix_tree_preload(GFP_NOFS))
>>> return;
>>>
>>> - mutex_lock(_lock);
>>> + spin_lock(_lock);
>>> p = radix_tree_lookup(, pid);
>>> if (p == current)
>>> goto out;
>>> if (p)
>>> radix_tree_delete(, pid);
>>>
>>> - f2fs_radix_tree_insert(, pid, current);
>>> + if (radix_tree_insert(, pid, current)) {
>>> + spin_unlock(_lock);
>>> + radix_tree_preload_end();
>>> + cond_resched();
>>> + goto retry;
>>> + }
>>>
>>> trace_printk("%3x:%3x %4x %-16s\n",
>>> MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
>>> pid, current->comm);
>>
>> Hi Sahitya,
>>
>> Can trace_printk sleep? For safety, how about moving it out of spinlock?
>>
> Hi Chao,
>
> Yes, trace_printk() is safe to use in atomic context (unlike printk).
Hi Sahitya,
Thanks for your confirmation. :)
Reviewed-by: Chao Yu
Thanks,
>
> Thanks,
> Sahitya.
>
>> Thanks,
>>
>>> out:
>>> - mutex_unlock(_lock);
>>> + spin_unlock(_lock);
>>> radix_tree_preload_end();
>>> }
>>>
>>> @@ -119,7 +125,7 @@ void f2fs_trace_ios(struct f2fs_io_info *fio, int flush)
>>>
>>> void f2fs_build_trace_ios(void)
>>> {
>>> - mutex_init(_lock);
>>> + spin_lock_init(_lock);
>>> }
>>>
>>> #define PIDVEC_SIZE128
>>> @@ -147,7 +153,7 @@ void f2fs_destroy_trace_ios(void)
>>> pid_t next_pid = 0;
>>> unsigned int found;
>>>
>>> - mutex_lock(_lock);
>>> + spin_lock(_lock);
>>> while ((found = gang_lookup_pids(pid, next_pid, PIDVEC_SIZE))) {
>>> unsigned idx;
>>>
>>> @@ -155,5 +161,5 @@ void f2fs_destroy_trace_ios(void)
>>> for (idx = 0; idx < found; idx++)
>>> radix_tree_delete(, pid[idx]);
>>> }
>>> - mutex_unlock(_lock);
>>> + spin_unlock(_lock);
>>> }
>>>
>>
>
