linux-kernel - Re: [PATCH] fs: inode_set_flags() replace opencoded set_mask

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Message-ID: <C2D7FE5348E1B147BCA15975FBA23075665B18EA@IN01WEMBXB.internal.synopsys.com>
Date:	Fri, 7 Aug 2015 11:40:23 +0000
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Theodore Ts'o <tytso@....edu>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs: inode_set_flags() replace opencoded set_mask_bits()

On Friday 07 August 2015 04:40 PM, Peter Zijlstra wrote:
> On Fri, Aug 07, 2015 at 12:25:04PM +0530, Vineet Gupta wrote:
>> > It seems that 5f16f3225b0624 and 00a1a053ebe5, both with same commitlog
>> > ("ext4: atomically set inode->i_flags in ext4_set_inode_flags()")
>> > introduced the set_mask_bits API, but somehow missed not using it in
>> > ext4 in the end
>> > 
>> > Also, set_mask_bits is used in fs quite a bit and we can possibly come up
>> > with a generic llsc based implementation (w/o the cmpxchg loop)
> May I also suggest changing the return value of set_mask_bits() to old.
>
> You can compute the new value given old, but you cannot compute the old
> value given new, therefore old is the better return value. Also, no
> current user seems to use the return value, so changing it is without
> risk.

Makes sense - will do that early next week !
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