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Message-ID: <20141210140347.GA23252@infradead.org> Date: Wed, 10 Dec 2014 06:03:47 -0800 From: Christoph Hellwig <hch@...radead.org> To: Matthew Wilcox <matthew.r.wilcox@...el.com> Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, willy@...ux.intel.com, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH v12 00/20] DAX: Page cache bypass for filesystems on memory storage What is the status of this patch set? On Fri, Oct 24, 2014 at 05:20:32PM -0400, Matthew Wilcox wrote: > DAX is a replacement for the variation of XIP currently supported by > the ext2 filesystem. We have three different things in the tree called > 'XIP', and the new focus is on access to data rather than executables, > so a name change was in order. DAX stands for Direct Access. The X is > for eXciting. > > The new focus on data access has resulted in more careful attention to > races that exist in the current XIP code, but are not hit by the use-case > that it was designed for. XIP's architecture worked fine for ext2, but > DAX is architected to work with modern filsystems such as ext4 and XFS. > DAX is not intended for use with btrfs; the value that btrfs adds relies > on manipulating data and writing data to different locations, while DAX's > value is for write-in-place and keeping the kernel from touching the data. > > DAX was developed in order to support NV-DIMMs, but it's become clear that > its usefuless extends beyond NV-DIMMs and there are several potential > customers including the tracing machinery. Other people want to place > the kernel log in an area of memory, as long as they have a BIOS that > does not clear DRAM on reboot. > > Patch 1 is a bug fix. It is obviously correct, and should be included > into 3.18. > > Patch 2 starts the transformation by changing how ->direct_access works. > Much code is moved from the drivers and filesystems into the block layer, > and we add the flexibility of being able to map more than one page at > a time. It would be good to get this patch into 3.18 as it is also > useful for people who are pursuing non-DAX approaches to working with > persistent memory. > > Patch 3 is also a bug fix, probably worth including in 3.18. > > Patches 4 & 5 are infrastructure for DAX. > > Patches 6-10 replace the XIP code with its DAX equivalents, transforming > ext2 to use the DAX code as we go. Note that patch 10 is the > Documentation patch. > > Patches 11-17 clean up after the XIP code, removing the infrastructure > that is no longer needed and renaming various XIP things to DAX. > Most of these patches were added after Jan found things he didn't > like in an earlier version of the ext4 patch ... that had been copied > from ext2. So ext2 i being transformed to do things the same way that > ext4 will later. The ability to mount ext2 filesystems with the 'xip' > option is retained, although the 'dax' option is now preferred. > > Patch 18 adds some DAX infrastructure to support ext4. > > Patch 19 adds DAX support to ext4. It is broadly similar to ext2's DAX > support, but it is more efficient than ext4's due to its support for > unwritten extents. > > Patch 20 is another cleanup patch renaming XIP to DAX. > > > My thanks to Mathieu Desnoyers for his reviews of the v11 patchset. Most > of the changes below were based on his feedback. > > Changes since v11: > - Rebased to 3.18-rc1, dropping patch "vfs: Add copy_to_iter(), > copy_from_iter() and iov_iter_zero()" as it was merged through Al's tree. > - Added cc to stable@...r.kernel.org on patch 1 > - Fixed comment style in brd.c (Mathieu) > - Make more functions in fs.h common with and without CONFIG_FS_DAX set > - Improve type-checking with !CONFIG_FS_DAX > - Simplify check for holes in dax_io() > - Harden the loop in dax_clear_blocks() > - Add missing check against truncate of a page covering a hole > - Fix the page-fault handler to work for block devices too > - Change a few more places that mentioned 'XIP' into 'DAX' > - Update DAX documentation in a couple of places > > Matthew Wilcox (19): > axonram: Fix bug in direct_access > block: Change direct_access calling convention > mm: Fix XIP fault vs truncate race > mm: Allow page fault handlers to perform the COW > vfs,ext2: Introduce IS_DAX(inode) > dax,ext2: Replace XIP read and write with DAX I/O > dax,ext2: Replace ext2_clear_xip_target with dax_clear_blocks > dax,ext2: Replace the XIP page fault handler with the DAX page fault > handler > dax,ext2: Replace xip_truncate_page with dax_truncate_page > dax: Replace XIP documentation with DAX documentation > vfs: Remove get_xip_mem > ext2: Remove ext2_xip_verify_sb() > ext2: Remove ext2_use_xip > ext2: Remove xip.c and xip.h > vfs,ext2: Remove CONFIG_EXT2_FS_XIP and rename CONFIG_FS_XIP to > CONFIG_FS_DAX > ext2: Remove ext2_aops_xip > ext2: Get rid of most mentions of XIP in ext2 > dax: Add dax_zero_page_range > brd: Rename XIP to DAX > > Ross Zwisler (1): > ext4: Add DAX functionality > > Documentation/filesystems/00-INDEX | 5 +- > Documentation/filesystems/Locking | 3 - > Documentation/filesystems/dax.txt | 91 +++++++ > Documentation/filesystems/ext2.txt | 5 +- > Documentation/filesystems/ext4.txt | 4 + > Documentation/filesystems/vfs.txt | 7 - > Documentation/filesystems/xip.txt | 68 ----- > MAINTAINERS | 6 + > arch/powerpc/sysdev/axonram.c | 19 +- > drivers/block/Kconfig | 13 +- > drivers/block/brd.c | 28 +- > drivers/s390/block/dcssblk.c | 21 +- > fs/Kconfig | 21 +- > fs/Makefile | 1 + > fs/block_dev.c | 40 +++ > fs/dax.c | 530 +++++++++++++++++++++++++++++++++++++ > fs/exofs/inode.c | 1 - > fs/ext2/Kconfig | 11 - > fs/ext2/Makefile | 1 - > fs/ext2/ext2.h | 10 +- > fs/ext2/file.c | 45 +++- > fs/ext2/inode.c | 38 +-- > fs/ext2/namei.c | 13 +- > fs/ext2/super.c | 53 ++-- > fs/ext2/xip.c | 91 ------- > fs/ext2/xip.h | 26 -- > fs/ext4/ext4.h | 6 + > fs/ext4/file.c | 50 +++- > fs/ext4/indirect.c | 18 +- > fs/ext4/inode.c | 89 +++++-- > fs/ext4/namei.c | 10 +- > fs/ext4/super.c | 39 ++- > fs/open.c | 5 +- > include/linux/blkdev.h | 6 +- > include/linux/fs.h | 34 +-- > include/linux/mm.h | 1 + > include/linux/rmap.h | 2 +- > mm/Makefile | 1 - > mm/fadvise.c | 6 +- > mm/filemap.c | 25 +- > mm/filemap_xip.c | 483 --------------------------------- > mm/madvise.c | 2 +- > mm/memory.c | 33 ++- > scripts/diffconfig | 1 - > 44 files changed, 1069 insertions(+), 893 deletions(-) > create mode 100644 Documentation/filesystems/dax.txt > delete mode 100644 Documentation/filesystems/xip.txt > create mode 100644 fs/dax.c > delete mode 100644 fs/ext2/xip.c > delete mode 100644 fs/ext2/xip.h > delete mode 100644 mm/filemap_xip.c > > -- > 2.1.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html ---end quoted text--- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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