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Date: Mon, 23 May 2022 11:40:23 +0200 From: Jan Kara <jack@...e.cz> To: Baokun Li <libaokun1@...wei.com> Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com, 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 On Sat 21-05-22 21:42:17, 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. > In this case, it should be bug_ON. > > Fixes: dfe076c106f6 ("ext4: get rid of code duplication") > Signed-off-by: Baokun Li <libaokun1@...wei.com> I think this is actually wrong. The original condition checks whether start + size does not overflow the used integer type. Your condition is much stronger and I don't think it always has to be true. E.g. allocation goal block (start variable) can be pushed to larger values by existing preallocation or so. Honza > 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 > -- Jan Kara <jack@...e.com> SUSE Labs, CR
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