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    SubjectRe: [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@huawei.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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