From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 2 Mar 2018 09:45:30 -0800 From: "Darrick J. Wong" Subject: Re: [PATCH v5 02/12] dax: introduce IS_DEVDAX() and IS_FSDAX() Message-ID: <20180302174530.GV19312@magnolia> References: <151996281307.28483.12343847096989509127.stgit@dwillia2-desk3.amr.corp.intel.com> <151996282448.28483.10415125852182473579.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <151996282448.28483.10415125852182473579.stgit@dwillia2-desk3.amr.corp.intel.com> Sender: owner-linux-mm@kvack.org To: Dan Williams Cc: linux-nvdimm@lists.01.org, Theodore Ts'o , Andreas Dilger , Alexander Viro , linux-xfs@vger.kernel.org, Matthew Wilcox , Ross Zwisler , stable@vger.kernel.org, Jan Kara , hch@lst.de, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Thu, Mar 01, 2018 at 07:53:44PM -0800, Dan Williams wrote: > The current IS_DAX() helper that checks if a file is in DAX mode serves > two purposes. It is a control flow branch condition for DAX vs > non-DAX paths and it is a mechanism to perform dead code elimination. The > dead code elimination is required in the CONFIG_FS_DAX=n case since > there are symbols in fs/dax.c that will be elided. While the > dead code elimination can be addressed with nop stubs for the fs/dax.c > symbols that does not address the need for a DAX control flow helper > where fs/dax.c symbols are not involved. > > Moreover, the control flow changes, in some cases, need to be cognizant > of whether the DAX file is a typical file or a Device-DAX special file. > Introduce IS_DEVDAX() and IS_FSDAX() to simultaneously address the > file-type control flow and dead-code elimination use cases. IS_DAX() > will be deleted after all sites are converted to use the file-type > specific helper. > > Note, this change is also a pre-requisite for fixing the definition of > the S_DAX inode flag in the CONFIG_FS_DAX=n + CONFIG_DEV_DAX=y case. > The flag needs to be defined, non-zero, if either DAX facility is > enabled. > > Cc: "Theodore Ts'o" > Cc: Andreas Dilger > Cc: Alexander Viro > Cc: "Darrick J. Wong" > Cc: linux-xfs@vger.kernel.org > Cc: Matthew Wilcox > Cc: Ross Zwisler > Cc: > Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") > Reported-by: Jan Kara > Reviewed-by: Jan Kara > Signed-off-by: Dan Williams > --- > include/linux/fs.h | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 79c413985305..bd0c46880572 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1909,6 +1909,28 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags > #define IS_WHITEOUT(inode) (S_ISCHR(inode->i_mode) && \ > (inode)->i_rdev == WHITEOUT_DEV) > > +static inline bool IS_DEVDAX(struct inode *inode) > +{ > + if (!IS_ENABLED(CONFIG_DEV_DAX)) > + return false; > + if ((inode->i_flags & S_DAX) == 0) > + return false; > + if (!S_ISCHR(inode->i_mode)) > + return false; > + return true; > +} > + > +static inline bool IS_FSDAX(struct inode *inode) > +{ > + if (!IS_ENABLED(CONFIG_FS_DAX)) > + return false; I echo Jan's complaint from the last round that the dead code elimination here is subtle, as compared to: #if IS_ENABLED(CONFIG_FS_DAX) static inline bool IS_FSDAX(struct inode *inode) { ... } #else # define IS_FSDAX(inode) (false) #endif But I guess even with that we're relying on dead code elimination higher up in the call stack... > + if ((inode->i_flags & S_DAX) == 0) > + return false; > + if (S_ISCHR(inode->i_mode)) > + return false; I'm curious, do we have character devices with S_DAX set? I /think/ we're expecting that only block/char devices and files will ever have S_DAX set, so IS_FSDAX is only true for block devices and files. Right? (A comment here about why S_ISCHR->false here would be helpful.) --D > + return true; > +} > + > static inline bool HAS_UNMAPPED_ID(struct inode *inode) > { > return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid); > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2080671-1520012757-2-12728960360616617064 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.249, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, UNPARSEABLE_RELAY 0.001, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='com', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520012756; b=Jetqt+ApWER6yDcNBVZZjhvO2LLEwFTKmJi0j0+V3ELGHaZ wVgVhF6cZBsT6rQRXx2nBlWcZaBf9zOYpQ2NOqKc+ilLZdZX73GngB1djvXg0BS8 6P4h1tlUqoCXlUkHlnm1uNc1YTPj/0aFilvF8mXniQBuzJk8Meu4zL9GMtENGBIQ e6POKsvHLFxYG7NAu3fo4R8xLwQSz/3nf3euUykDvPg6uCzGOCJxynwzVs7HWOdE HXyksQzonjcWpG8t6vw2J9HcrQwdr8UMcCPMqmzfUuJ7GuQwOCMSHy+59xb7LqXz uupxOC1c+Vh6jIAIfYQkReZzyOPGudgCPNuZAvQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=arctest; t=1520012756; bh=oQv/naU0ffRqEAxYEVpNgigqhl EK8I6ogIeAyTAJVFk=; b=Atbf0tGmBZq0qAZLLEIm00bHzP7Xnz8gCkNKsPP530 et22KM4Cp7wmGqp192sDUqqMMWoc8K3cCUMj9KxU+y6AcQBRZqVfqqyWZqyigbDy nUsxai7BkCOCmbXpXxHATu69HPJs1jEpVA7YHkQJTB3MNUJYnYkgCsqjJ2kPOvmc WaNj15jL93gi/ES172/LAyFl766mqdz0hkN1qcy4iPrRyXbSAM/a/lJg6kmmbq3s a6oQR0Eby9E8ptSbQDctpfyJPOmIRGE2dzKKQm4Vb/9GAGW7JXfJ9Q3rmdoN/qXK vk/u5fYTKMvWJWRFYhSHLak8uYYJzN3ALgubZ88uQuNw== ARC-Authentication-Results: i=1; mx6.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=oracle.com header.i=@oracle.com header.b=cIB8YQHZ x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=corp-2017-10-26; dmarc=pass (p=none,has-list-id=yes,d=none) header.from=oracle.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=oracle.com header.result=pass header_is_org_domain=yes Authentication-Results: mx6.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=oracle.com header.i=@oracle.com header.b=cIB8YQHZ x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=corp-2017-10-26; dmarc=pass (p=none,has-list-id=yes,d=none) header.from=oracle.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=oracle.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946825AbeCBRpy (ORCPT ); Fri, 2 Mar 2018 12:45:54 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:57008 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946824AbeCBRpw (ORCPT ); Fri, 2 Mar 2018 12:45:52 -0500 Date: Fri, 2 Mar 2018 09:45:30 -0800 From: "Darrick J. Wong" To: Dan Williams Cc: linux-nvdimm@lists.01.org, "Theodore Ts'o" , Andreas Dilger , Alexander Viro , linux-xfs@vger.kernel.org, Matthew Wilcox , Ross Zwisler , stable@vger.kernel.org, Jan Kara , hch@lst.de, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 02/12] dax: introduce IS_DEVDAX() and IS_FSDAX() Message-ID: <20180302174530.GV19312@magnolia> References: <151996281307.28483.12343847096989509127.stgit@dwillia2-desk3.amr.corp.intel.com> <151996282448.28483.10415125852182473579.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <151996282448.28483.10415125852182473579.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8820 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1803020209 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Thu, Mar 01, 2018 at 07:53:44PM -0800, Dan Williams wrote: > The current IS_DAX() helper that checks if a file is in DAX mode serves > two purposes. It is a control flow branch condition for DAX vs > non-DAX paths and it is a mechanism to perform dead code elimination. The > dead code elimination is required in the CONFIG_FS_DAX=n case since > there are symbols in fs/dax.c that will be elided. While the > dead code elimination can be addressed with nop stubs for the fs/dax.c > symbols that does not address the need for a DAX control flow helper > where fs/dax.c symbols are not involved. > > Moreover, the control flow changes, in some cases, need to be cognizant > of whether the DAX file is a typical file or a Device-DAX special file. > Introduce IS_DEVDAX() and IS_FSDAX() to simultaneously address the > file-type control flow and dead-code elimination use cases. IS_DAX() > will be deleted after all sites are converted to use the file-type > specific helper. > > Note, this change is also a pre-requisite for fixing the definition of > the S_DAX inode flag in the CONFIG_FS_DAX=n + CONFIG_DEV_DAX=y case. > The flag needs to be defined, non-zero, if either DAX facility is > enabled. > > Cc: "Theodore Ts'o" > Cc: Andreas Dilger > Cc: Alexander Viro > Cc: "Darrick J. Wong" > Cc: linux-xfs@vger.kernel.org > Cc: Matthew Wilcox > Cc: Ross Zwisler > Cc: > Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") > Reported-by: Jan Kara > Reviewed-by: Jan Kara > Signed-off-by: Dan Williams > --- > include/linux/fs.h | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 79c413985305..bd0c46880572 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1909,6 +1909,28 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags > #define IS_WHITEOUT(inode) (S_ISCHR(inode->i_mode) && \ > (inode)->i_rdev == WHITEOUT_DEV) > > +static inline bool IS_DEVDAX(struct inode *inode) > +{ > + if (!IS_ENABLED(CONFIG_DEV_DAX)) > + return false; > + if ((inode->i_flags & S_DAX) == 0) > + return false; > + if (!S_ISCHR(inode->i_mode)) > + return false; > + return true; > +} > + > +static inline bool IS_FSDAX(struct inode *inode) > +{ > + if (!IS_ENABLED(CONFIG_FS_DAX)) > + return false; I echo Jan's complaint from the last round that the dead code elimination here is subtle, as compared to: #if IS_ENABLED(CONFIG_FS_DAX) static inline bool IS_FSDAX(struct inode *inode) { ... } #else # define IS_FSDAX(inode) (false) #endif But I guess even with that we're relying on dead code elimination higher up in the call stack... > + if ((inode->i_flags & S_DAX) == 0) > + return false; > + if (S_ISCHR(inode->i_mode)) > + return false; I'm curious, do we have character devices with S_DAX set? I /think/ we're expecting that only block/char devices and files will ever have S_DAX set, so IS_FSDAX is only true for block devices and files. Right? (A comment here about why S_ISCHR->false here would be helpful.) --D > + return true; > +} > + > static inline bool HAS_UNMAPPED_ID(struct inode *inode) > { > return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid); > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html