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Date: Tue, 24 May 2022 14:09:35 +0800 From: Baokun Li <libaokun1@...wei.com> To: Ritesh Harjani <ritesh.list@...il.com> CC: <linux-ext4@...r.kernel.org>, <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>, <linux-kernel@...r.kernel.org>, <yi.zhang@...wei.com>, <yebin10@...wei.com>, <yukuai3@...wei.com> Subject: Re: [PATCH 2/2] ext4: correct the judgment of BUG in ext4_mb_normalize_request 在 2022/5/24 4:08, Ritesh Harjani 写道: > On 22/05/21 09:42PM, Baokun Li wrote: >> When either of the "start + size <= ac->ac_o_ex.fe_logical" or >> "start > ac->ac_o_ex.fe_logical" conditions is met, it indicates >> that the fe_logical is not in the allocated range. > Sounds about right to me based on the logic in ext4_mb_use_inode_pa(). > We try to allocate/preallocate such that ac->ac_o_ex.fe_logical should fall > within the preallocated range. So if our start or start + size doesn't include > fe_logical then it is a bug in the ext4_mb_normalize_request() logic. Yes, exactly. > But should we be so harsh to hit a bug_on() or make it warn_on()? I don't think hit a bug_on() is a problem. BUG_ON is not triggered here and will be triggered later. > Also did you run any fs tests with this change. Yes, I ran xfstests on ext3 and ext4 and found no problems. > Since it looks like this > logic existed since mballoc was introduced. > Yes, on our coverage report, those lines of code never seem to get there. >> In this case, it should be bug_ON. >> >> Fixes: dfe076c106f6 ("ext4: get rid of code duplication") > No, there is no issue with this patch. It correctly just removes the duplicate > logic. Okay, I'm going to remove this tag. >> Signed-off-by: Baokun Li<libaokun1@...wei.com> >> --- >> fs/ext4/mballoc.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c >> index 32410b79b664..d0fb57970648 100644 >> --- a/fs/ext4/mballoc.c >> +++ b/fs/ext4/mballoc.c >> @@ -4190,7 +4190,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, >> } >> rcu_read_unlock(); >> >> - if (start + size <= ac->ac_o_ex.fe_logical && >> + if (start + size <= ac->ac_o_ex.fe_logical || >> start > ac->ac_o_ex.fe_logical) { >> ext4_msg(ac->ac_sb, KERN_ERR, >> "start %lu, size %lu, fe_logical %lu", >> -- >> 2.31.1 >> > . -- With Best Regards, Baokun Li
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