linux-kernel - Re: [PATCH] pstore: avoid incorrectly mark entry as duplicate

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Message-ID: <87ob6g55n9.fsf@redhat.com>
Date:	Thu, 24 Oct 2013 00:11:22 +0800
From:	Madper Xie <cxie@...hat.com>
To:	Richard Weinberger <richard.weinberger@...il.com>
Cc:	Madper Xie <cxie@...hat.com>, "Luck\, Tony" <tony.luck@...el.com>,
	Anton Vorontsov <anton@...msg.org>,
	"linux-efi\@vger.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Seiji Aguchi <seiji.aguchi@....com>,
	Lenny Szubowicz <lszubowi@...hat.com>,
	成骏 谢 <bbboson@...il.com>
Subject: Re: [PATCH] pstore: avoid incorrectly mark entry as duplicate


richard.weinberger@...il.com writes:

> On Wed, Oct 23, 2013 at 4:55 PM, Madper Xie <cxie@...hat.com> wrote:
>> pstore try to find duplicate entries by check both ID, type and psi.
>> They are not really enough for efi backend. dumped vars always have
>> the same type, psi and ID. like follows:
>> dump-type0-9-1-1382511508-C-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0
>> dump-type0-9-1-1382515661-C-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0
>>
>> The "duplicate" entries won't appear in pstorefs. And a complain will be
>> print -- pstore: failed to load 76 record(s) from 'efi'
>> So I add one more check: timespec.
>>
>> Signed-off-by: Madper Xie <cxie@...hat.com>
>> ---
>>  fs/pstore/inode.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
>> index 1282384..f70f1e5 100644
>> --- a/fs/pstore/inode.c
>> +++ b/fs/pstore/inode.c
>> @@ -47,6 +47,7 @@ static LIST_HEAD(allpstore);
>>  struct pstore_private {
>>         struct list_head list;
>>         struct pstore_info *psi;
>> +       struct timespec time;
>>         enum pstore_type_id type;
>>         u64     id;
>>         int     count;
>> @@ -290,7 +291,8 @@ int pstore_mkfile(enum pstore_type_id type, char *psname, u64 id, int count,
>>         list_for_each_entry(pos, &allpstore, list) {
>>                 if (pos->type == type &&
>>                     pos->id == id &&
>> -                   pos->psi == psi) {
>> +                   pos->psi == psi &&
>> +                   !timespec_compare(&pos->time, &time)) {
>>                         rc = -EEXIST;
>>                         break;
>>                 }
>> @@ -312,6 +314,7 @@ int pstore_mkfile(enum pstore_type_id type, char *psname, u64 id, int count,
>>         private->id = id;
>>         private->count = count;
>>         private->psi = psi;
>> +       memcpy(&private->time, &time, sizeof(struct timespec));
>>
>>         switch (type) {
>>         case PSTORE_TYPE_DMESG:
>
>
> As discussed on IRC, why don't you compare the variable names?
Howdy Richard,
  Let's analyze the name of "duplicate" entries:
>> dump-type0-9-1-1382511508-C-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0
>> dump-type0-9-1-1382515661-C-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0
  The have the same name except timestamp. In this case, there is no
  difference between compare names and compare timestamps.
  ( Yeah, I'm pretty sure the guid will be the same one --
  LINUX_EFI_CRASH_GUID )
  But efi is only one backend. For other backends, we don't sure if they
  will add timestamp to name. So...
  
-- 
Best,
Madper Xie.
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