The functions metapage_writepage() and lmPostGC() can be concurrently
executed in the following call contexts:
Thread1:
metapage_writepage()
Thread2:
lbmIODone()
lmPostGC()
In metapage_writepage():
if (mp->log && !(mp->log->cflag & logGC_PAGEOUT))
In lmPostGC():
spin_lock_irqsave(&log->gclock, flags);
...
log->cflag &= ~logGC_PAGEOUT
...
spin_unlock_irqrestore(&log->gclock, flags);
The memory addresses of mp->log->cflag and log->cflag can be identical,
and thus a data race can occur.
This data race is found by our concurrency fuzzer.
Thus use the spin lock "mp->log->gclock" for the assignment of
the data structure member "log->cflag" to a local variable
in this function implementation.
Signed-off-by: Jia-Ju Bai <[email protected]>
---
v2:
* Change the description.
Thank Markus Elfring for good advice.
---
fs/jfs/jfs_metapage.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
index a2f5338a5ea1..026c11b2572d 100644
--- a/fs/jfs/jfs_metapage.c
+++ b/fs/jfs/jfs_metapage.c
@@ -351,6 +351,7 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
unsigned long bio_offset = 0;
int offset;
int bad_blocks = 0;
+ uint cflag;
page_start = (sector_t)page->index <<
(PAGE_SHIFT - inode->i_blkbits);
@@ -370,8 +371,14 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
* Make sure this page isn't blocked indefinitely.
* If the journal isn't undergoing I/O, push it
*/
- if (mp->log && !(mp->log->cflag & logGC_PAGEOUT))
- jfs_flush_journal(mp->log, 0);
+
+ if (mp->log) {
+ spin_lock_irq(&mp->log->gclock);
+ cflag = mp->log->cflag;
+ spin_unlock_irq(&mp->log->gclock);
+ if (!(cflag & logGC_PAGEOUT))
+ jfs_flush_journal(mp->log, 0);
+ }
continue;
}
--
2.17.1
> This data race is found by our concurrency fuzzer.
* How do you think about to replace the word “is” by “was”?
* Is this analysis tool publicly available?
…
> ---
> fs/jfs/jfs_metapage.c | 11 +++++++++--
I suggest to omit the triple dashes before this information.
Regards,
Markus
On 2020/5/5 22:15, Markus Elfring wrote:
>> This data race is found by our concurrency fuzzer.
> * How do you think about to replace the word “is” by “was”?
Okay.
> * Is this analysis tool publicly available?
Not yet, because we are still developing this tool...
>
> …
>> ---
>> fs/jfs/jfs_metapage.c | 11 +++++++++--
> I suggest to omit the triple dashes before this information.
Okay, thanks.
Best wishes,
Jia-Ju Bai
On 5/5/20 9:15 AM, Markus Elfring wrote:
>> This data race is found by our concurrency fuzzer.
>
> * How do you think about to replace the word “is” by “was”?
>
> * Is this analysis tool publicly available?
>
>
> …
>> ---
>> fs/jfs/jfs_metapage.c | 11 +++++++++--
>
> I suggest to omit the triple dashes before this information.
That's standard. There's no need to the diffstat to persist in the
commit message.
>
> Regards,
> Markus
>
>>> This data race is found by our concurrency fuzzer.
>> * How do you think about to replace the word “is” by “was”?
>
> Okay.
Can such a positive feedback influence the change descriptions
for any of your other patches?
Regards,
Markus
On 2020/5/5 22:32, Markus Elfring wrote:
>>>> This data race is found by our concurrency fuzzer.
>>> * How do you think about to replace the word “is” by “was”?
>> Okay.
> Can such a positive feedback influence the change descriptions
> for any of your other patches?
Okay, sure, thanks for the advice.
I will resend my patches for jfs.
Best wishes,
Jia-Ju Bai