From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-194.mimecast.com ([63.128.21.194]:21479 "EHLO us-smtp-delivery-194.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753129AbeA3RuN (ORCPT ); Tue, 30 Jan 2018 12:50:13 -0500 From: Trond Myklebust To: "torvalds@linux-foundation.org" , "jlayton@kernel.org" CC: "linux-integrity@vger.kernel.org" , "linux-xfs@vger.kernel.org" , "linux-nfs@vger.kernel.org" , "viro@zeniv.linux.org.uk" , "akpm@linux-foundation.org" , "linux-btrfs@vger.kernel.org" , "linux-ext4@vger.kernel.org" , "tytso@mit.edu" Subject: Re: [PATCH] iversion: make inode_cmp_iversion{+raw} return bool instead of s64 Date: Tue, 30 Jan 2018 17:50:05 +0000 Message-ID: <1517334602.5412.3.camel@primarydata.com> References: <20180130173126.2806-1-jlayton@kernel.org> In-Reply-To: <20180130173126.2806-1-jlayton@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Tue, 2018-01-30 at 12:31 -0500, Jeff Layton wrote: > From: Jeff Layton > > As Linus points out: > > The inode_cmp_iversion{+raw}() functions are pure and utter crap. > > Why? > > You say that they return 0/negative/positive, but they do so in a > completely broken manner. They return that ternary value as the > sequence number difference in a 's64', which means that if you > actually care about that ternary value, and do the *sane* thing > that > the kernel-doc of the function implies is the right thing, you > would > do > > int cmp = inode_cmp_iversion(inode, old); > if (cmp < 0 ... > > and as a result you get code that looks sane, but that doesn't > actually *WORK* right. > > Since none of the callers actually care about the ternary value here, > convert the inode_cmp_iversion{+raw} functions to just return a > boolean > value (false for matching, true for non-matching). > > This matches the existing use of these functions just fine, and makes > it > simple to convert them to return a ternary value in the future if we > grow callers that need it. > > Signed-off-by: Jeff Layton > --- > include/linux/iversion.h | 20 +++++++++----------- > 1 file changed, 9 insertions(+), 11 deletions(-) > > diff --git a/include/linux/iversion.h b/include/linux/iversion.h > index 858463fca249..ace32775c5f0 100644 > --- a/include/linux/iversion.h > +++ b/include/linux/iversion.h > @@ -309,13 +309,13 @@ inode_query_iversion(struct inode *inode) > * @inode: inode to check > * @old: old value to check against its i_version > * > - * Compare the current raw i_version counter with a previous one. > Returns 0 if > - * they are the same or non-zero if they are different. > + * Compare the current raw i_version counter with a previous one. > Returns false > + * if they are the same or true if they are different. > */ > -static inline s64 > +static inline bool > inode_cmp_iversion_raw(const struct inode *inode, u64 old) > { > - return (s64)inode_peek_iversion_raw(inode) - (s64)old; > + return inode_peek_iversion_raw(inode) != old; > } > > /** > @@ -323,19 +323,17 @@ inode_cmp_iversion_raw(const struct inode > *inode, u64 old) > * @inode: inode to check > * @old: old value to check against its i_version > * > - * Compare an i_version counter with a previous one. Returns 0 if > they are > - * the same, a positive value if the one in the inode appears newer > than @old, > - * and a negative value if @old appears to be newer than the one in > the > - * inode. > + * Compare an i_version counter with a previous one. Returns false > if they are > + * the same, and true if they are different. > * > * Note that we don't need to set the QUERIED flag in this case, as > the value > * in the inode is not being recorded for later use. > */ > > -static inline s64 > +static inline bool > inode_cmp_iversion(const struct inode *inode, u64 old) > { > - return (s64)(inode_peek_iversion_raw(inode) & > ~I_VERSION_QUERIED) - > - (s64)(old << I_VERSION_QUERIED_SHIFT); > + return (inode_peek_iversion_raw(inode) & ~I_VERSION_QUERIED) > != > + (old << I_VERSION_QUERIED_SHIFT); > } Is there any reason why this couldn't just use inode_peek_iversion() instead of having to both mask the output from inode_peek_iversion_raw() and shift 'old'? > #endif -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@primarydata.com {.n++%ݶw{.n+{k~^nrzh&zzޗ++zfh~iz_j:+v)ߣm