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Ts'o" To: adam.manzanares@wdc.com Cc: viro@zeniv.linux.org.uk, bcrl@kvack.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-api@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/3] fs: Convert kiocb rw_hint from enum to u16 Message-ID: <20180509133432.GD28388@thunk.org> Mail-Followup-To: "Theodore Y. Ts'o" , adam.manzanares@wdc.com, viro@zeniv.linux.org.uk, bcrl@kvack.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-api@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20180508174202.2537-1-adam.manzanares@wdc.com> <20180508174202.2537-3-adam.manzanares@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180508174202.2537-3-adam.manzanares@wdc.com> User-Agent: Mutt/1.9.5 (2018-04-13) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Tue, May 08, 2018 at 10:42:01AM -0700, adam.manzanares@wdc.com wrote: > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 760d8da1b6c7..7a90ce387e00 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -284,6 +284,8 @@ enum rw_hint { > WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME, > }; > > +#define MAX_KI_HINT ((1 << 16) - 1) /* ki_hint type is u16 */ > + Do we really think there will be *ever* be a need for more than 16 I/O priority levels? I would much rather use the low four bits of KI_HINT for the priority level, and reserve the rest of the 16 bits in KI_HINT for some future use. (For example, we might want to use some number of bits for a stream ID.) - Ted