From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934141AbbLWAQd (ORCPT ); Tue, 22 Dec 2015 19:16:33 -0500 Received: from mga04.intel.com ([192.55.52.120]:62680 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932594AbbLWAQb (ORCPT ); Tue, 22 Dec 2015 19:16:31 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,466,1444719600"; d="scan'208";a="17900463" Date: Tue, 22 Dec 2015 17:16:27 -0700 From: Ross Zwisler To: Andrew Morton Cc: Ross Zwisler , linux-kernel@vger.kernel.org, "H. Peter Anvin" , "J. Bruce Fields" , "Theodore Ts'o" , Alexander Viro , Andreas Dilger , Dave Chinner , Ingo Molnar , Jan Kara , Jeff Layton , Matthew Wilcox , Thomas Gleixner , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, x86@kernel.org, xfs@oss.sgi.com, Dan Williams , Matthew Wilcox , Dave Hansen Subject: Re: [PATCH v5 2/7] dax: support dirty DAX entries in radix tree Message-ID: <20151223001627.GC24124@linux.intel.com> Mail-Followup-To: Ross Zwisler , Andrew Morton , linux-kernel@vger.kernel.org, "H. Peter Anvin" , "J. Bruce Fields" , Theodore Ts'o , Alexander Viro , Andreas Dilger , Dave Chinner , Ingo Molnar , Jan Kara , Jeff Layton , Matthew Wilcox , Thomas Gleixner , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, x86@kernel.org, xfs@oss.sgi.com, Dan Williams , Matthew Wilcox , Dave Hansen References: <1450502540-8744-1-git-send-email-ross.zwisler@linux.intel.com> <1450502540-8744-3-git-send-email-ross.zwisler@linux.intel.com> <20151222144605.08a84ded98a42d6125a7991e@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151222144605.08a84ded98a42d6125a7991e@linux-foundation.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 22, 2015 at 02:46:05PM -0800, Andrew Morton wrote: > On Fri, 18 Dec 2015 22:22:15 -0700 Ross Zwisler wrote: > > > Add support for tracking dirty DAX entries in the struct address_space > > radix tree. This tree is already used for dirty page writeback, and it > > already supports the use of exceptional (non struct page*) entries. > > > > In order to properly track dirty DAX pages we will insert new exceptional > > entries into the radix tree that represent dirty DAX PTE or PMD pages. > > These exceptional entries will also contain the writeback addresses for the > > PTE or PMD faults that we can use at fsync/msync time. > > > > There are currently two types of exceptional entries (shmem and shadow) > > that can be placed into the radix tree, and this adds a third. We rely on > > the fact that only one type of exceptional entry can be found in a given > > radix tree based on its usage. This happens for free with DAX vs shmem but > > we explicitly prevent shadow entries from being added to radix trees for > > DAX mappings. > > > > The only shadow entries that would be generated for DAX radix trees would > > be to track zero page mappings that were created for holes. These pages > > would receive minimal benefit from having shadow entries, and the choice > > to have only one type of exceptional entry in a given radix tree makes the > > logic simpler both in clear_exceptional_entry() and in the rest of DAX. > > > > > > ... > > > > --- a/include/linux/dax.h > > +++ b/include/linux/dax.h > > @@ -36,4 +36,9 @@ static inline bool vma_is_dax(struct vm_area_struct *vma) > > { > > return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host); > > } > > + > > +static inline bool dax_mapping(struct address_space *mapping) > > +{ > > + return mapping->host && IS_DAX(mapping->host); > > +} > > Can we make this evaluate to plain old "0" when CONFIG_FS_DAX=n? That > way a bunch of code in callers will fall away as well. > > If the compiler has any brains then a good way to do this would be to > make IS_DAX be "0" but one would need to check that the zeroness > properly propagated out of the inline. Ah, it already works that way due to some magic with IS_DAX(). I believe we already use the fact that blocks protected by IS_DAX() go away if CONFIG_FS_DAX isn't set. The trick is that S_DAX is defined to be 0 if CONFIG_FS_DAX isn't set. I'm pretty sure this is working because of the code in filemap_write_and_wait_range(). I added a block with the later "dax: add support for fsync/msync" patch which looks like this: @@ -482,6 +482,9 @@ int filemap_write_and_wait_range(struct address_space *mapping, { int err = 0; + if (dax_mapping(mapping) && mapping->nrdax) + dax_writeback_mapping_range(mapping, lstart, lend); + Without the dax_mapping() check there the behavior is the same, but we fail to compile if CONFIG_FS_DAX isn't set because dax_writeback_mapping_range() isn't defined. (Guess how I found that out. :) ) > > #endif > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 3aa5142..b9ac534 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -433,6 +433,7 @@ struct address_space { > > /* Protected by tree_lock together with the radix tree */ > > unsigned long nrpages; /* number of total pages */ > > unsigned long nrshadows; /* number of shadow entries */ > > + unsigned long nrdax; /* number of DAX entries */ > > hm, that's unfortunate - machines commonly carry tremendous numbers of > address_spaces in memory and adding pork to them is rather a big deal. > We can't avoid this somehow? Maybe share the space with nrshadows by > some means? Find some other field which is unused for dax files? Jan Kara noticed the same thing: https://lists.01.org/pipermail/linux-nvdimm/2015-December/003626.html It'll be fixed in the next spin of the patch set. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 22 Dec 2015 17:16:27 -0700 From: Ross Zwisler To: Andrew Morton Cc: Ross Zwisler , linux-kernel@vger.kernel.org, "H. Peter Anvin" , "J. Bruce Fields" , Theodore Ts'o , Alexander Viro , Andreas Dilger , Dave Chinner , Ingo Molnar , Jan Kara , Jeff Layton , Matthew Wilcox , Thomas Gleixner , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, x86@kernel.org, xfs@oss.sgi.com, Dan Williams , Matthew Wilcox , Dave Hansen Subject: Re: [PATCH v5 2/7] dax: support dirty DAX entries in radix tree Message-ID: <20151223001627.GC24124@linux.intel.com> References: <1450502540-8744-1-git-send-email-ross.zwisler@linux.intel.com> <1450502540-8744-3-git-send-email-ross.zwisler@linux.intel.com> <20151222144605.08a84ded98a42d6125a7991e@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151222144605.08a84ded98a42d6125a7991e@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: On Tue, Dec 22, 2015 at 02:46:05PM -0800, Andrew Morton wrote: > On Fri, 18 Dec 2015 22:22:15 -0700 Ross Zwisler wrote: > > > Add support for tracking dirty DAX entries in the struct address_space > > radix tree. This tree is already used for dirty page writeback, and it > > already supports the use of exceptional (non struct page*) entries. > > > > In order to properly track dirty DAX pages we will insert new exceptional > > entries into the radix tree that represent dirty DAX PTE or PMD pages. > > These exceptional entries will also contain the writeback addresses for the > > PTE or PMD faults that we can use at fsync/msync time. > > > > There are currently two types of exceptional entries (shmem and shadow) > > that can be placed into the radix tree, and this adds a third. We rely on > > the fact that only one type of exceptional entry can be found in a given > > radix tree based on its usage. This happens for free with DAX vs shmem but > > we explicitly prevent shadow entries from being added to radix trees for > > DAX mappings. > > > > The only shadow entries that would be generated for DAX radix trees would > > be to track zero page mappings that were created for holes. These pages > > would receive minimal benefit from having shadow entries, and the choice > > to have only one type of exceptional entry in a given radix tree makes the > > logic simpler both in clear_exceptional_entry() and in the rest of DAX. > > > > > > ... > > > > --- a/include/linux/dax.h > > +++ b/include/linux/dax.h > > @@ -36,4 +36,9 @@ static inline bool vma_is_dax(struct vm_area_struct *vma) > > { > > return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host); > > } > > + > > +static inline bool dax_mapping(struct address_space *mapping) > > +{ > > + return mapping->host && IS_DAX(mapping->host); > > +} > > Can we make this evaluate to plain old "0" when CONFIG_FS_DAX=n? That > way a bunch of code in callers will fall away as well. > > If the compiler has any brains then a good way to do this would be to > make IS_DAX be "0" but one would need to check that the zeroness > properly propagated out of the inline. Ah, it already works that way due to some magic with IS_DAX(). I believe we already use the fact that blocks protected by IS_DAX() go away if CONFIG_FS_DAX isn't set. The trick is that S_DAX is defined to be 0 if CONFIG_FS_DAX isn't set. I'm pretty sure this is working because of the code in filemap_write_and_wait_range(). I added a block with the later "dax: add support for fsync/msync" patch which looks like this: @@ -482,6 +482,9 @@ int filemap_write_and_wait_range(struct address_space *mapping, { int err = 0; + if (dax_mapping(mapping) && mapping->nrdax) + dax_writeback_mapping_range(mapping, lstart, lend); + Without the dax_mapping() check there the behavior is the same, but we fail to compile if CONFIG_FS_DAX isn't set because dax_writeback_mapping_range() isn't defined. (Guess how I found that out. :) ) > > #endif > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 3aa5142..b9ac534 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -433,6 +433,7 @@ struct address_space { > > /* Protected by tree_lock together with the radix tree */ > > unsigned long nrpages; /* number of total pages */ > > unsigned long nrshadows; /* number of shadow entries */ > > + unsigned long nrdax; /* number of DAX entries */ > > hm, that's unfortunate - machines commonly carry tremendous numbers of > address_spaces in memory and adding pork to them is rather a big deal. > We can't avoid this somehow? Maybe share the space with nrshadows by > some means? Find some other field which is unused for dax files? Jan Kara noticed the same thing: https://lists.01.org/pipermail/linux-nvdimm/2015-December/003626.html It'll be fixed in the next spin of the patch set. -- 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 From: Ross Zwisler Subject: Re: [PATCH v5 2/7] dax: support dirty DAX entries in radix tree Date: Tue, 22 Dec 2015 17:16:27 -0700 Message-ID: <20151223001627.GC24124@linux.intel.com> References: <1450502540-8744-1-git-send-email-ross.zwisler@linux.intel.com> <1450502540-8744-3-git-send-email-ross.zwisler@linux.intel.com> <20151222144605.08a84ded98a42d6125a7991e@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-nvdimm@ml01.01.org, Dave Hansen , "J. Bruce Fields" , linux-mm@kvack.org, Andreas Dilger , "H. Peter Anvin" , Jeff Layton , Dan Williams , x86@kernel.org, Ingo Molnar , Matthew Wilcox , Ross Zwisler , linux-ext4@vger.kernel.org, xfs@oss.sgi.com, Alexander Viro , Thomas Gleixner , Theodore Ts'o , linux-kernel@vger.kernel.org, Jan Kara , linux-fsdevel@vger.kernel.org, Matthew Wilcox To: Andrew Morton Return-path: Content-Disposition: inline In-Reply-To: <20151222144605.08a84ded98a42d6125a7991e@linux-foundation.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com List-Id: linux-ext4.vger.kernel.org On Tue, Dec 22, 2015 at 02:46:05PM -0800, Andrew Morton wrote: > On Fri, 18 Dec 2015 22:22:15 -0700 Ross Zwisler wrote: > > > Add support for tracking dirty DAX entries in the struct address_space > > radix tree. This tree is already used for dirty page writeback, and it > > already supports the use of exceptional (non struct page*) entries. > > > > In order to properly track dirty DAX pages we will insert new exceptional > > entries into the radix tree that represent dirty DAX PTE or PMD pages. > > These exceptional entries will also contain the writeback addresses for the > > PTE or PMD faults that we can use at fsync/msync time. > > > > There are currently two types of exceptional entries (shmem and shadow) > > that can be placed into the radix tree, and this adds a third. We rely on > > the fact that only one type of exceptional entry can be found in a given > > radix tree based on its usage. This happens for free with DAX vs shmem but > > we explicitly prevent shadow entries from being added to radix trees for > > DAX mappings. > > > > The only shadow entries that would be generated for DAX radix trees would > > be to track zero page mappings that were created for holes. These pages > > would receive minimal benefit from having shadow entries, and the choice > > to have only one type of exceptional entry in a given radix tree makes the > > logic simpler both in clear_exceptional_entry() and in the rest of DAX. > > > > > > ... > > > > --- a/include/linux/dax.h > > +++ b/include/linux/dax.h > > @@ -36,4 +36,9 @@ static inline bool vma_is_dax(struct vm_area_struct *vma) > > { > > return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host); > > } > > + > > +static inline bool dax_mapping(struct address_space *mapping) > > +{ > > + return mapping->host && IS_DAX(mapping->host); > > +} > > Can we make this evaluate to plain old "0" when CONFIG_FS_DAX=n? That > way a bunch of code in callers will fall away as well. > > If the compiler has any brains then a good way to do this would be to > make IS_DAX be "0" but one would need to check that the zeroness > properly propagated out of the inline. Ah, it already works that way due to some magic with IS_DAX(). I believe we already use the fact that blocks protected by IS_DAX() go away if CONFIG_FS_DAX isn't set. The trick is that S_DAX is defined to be 0 if CONFIG_FS_DAX isn't set. I'm pretty sure this is working because of the code in filemap_write_and_wait_range(). I added a block with the later "dax: add support for fsync/msync" patch which looks like this: @@ -482,6 +482,9 @@ int filemap_write_and_wait_range(struct address_space *mapping, { int err = 0; + if (dax_mapping(mapping) && mapping->nrdax) + dax_writeback_mapping_range(mapping, lstart, lend); + Without the dax_mapping() check there the behavior is the same, but we fail to compile if CONFIG_FS_DAX isn't set because dax_writeback_mapping_range() isn't defined. (Guess how I found that out. :) ) > > #endif > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 3aa5142..b9ac534 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -433,6 +433,7 @@ struct address_space { > > /* Protected by tree_lock together with the radix tree */ > > unsigned long nrpages; /* number of total pages */ > > unsigned long nrshadows; /* number of shadow entries */ > > + unsigned long nrdax; /* number of DAX entries */ > > hm, that's unfortunate - machines commonly carry tremendous numbers of > address_spaces in memory and adding pork to them is rather a big deal. > We can't avoid this somehow? Maybe share the space with nrshadows by > some means? Find some other field which is unused for dax files? Jan Kara noticed the same thing: https://lists.01.org/pipermail/linux-nvdimm/2015-December/003626.html It'll be fixed in the next spin of the patch set. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs