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2021-06-04docs: convert dax.txt to rstIgor Matheus Andrade Torrente1-257/+0
Change the file extension and add the rst constructs to integrate this doc to the documentation infrastructure and take advantage of rst features. Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@gmail.com> Link: https://lore.kernel.org/r/20210531130515.10309-1-igormtorrente@gmail.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-01-11Documentation/dax: Update description of DAX policy changingHao Li1-14/+3
After commit 77573fa310d9 ("fs: Kill DCACHE_DONTCACHE dentry even if DCACHE_REFERENCED is set"), changes to DAX policy will take effect as soon as all references to this file are gone. Update the documentation accordingly. Signed-off-by: Hao Li <lihao2018.fnst@cn.fujitsu.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Link: https://lore.kernel.org/r/20210106015000.5263-1-lihao2018.fnst@cn.fujitsu.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-06-15Merge tag 'ext4-for-linus-5.8-rc1-2' of ↵Linus Torvalds1-3/+3
git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 Pull more ext4 updates from Ted Ts'o: "This is the second round of ext4 commits for 5.8 merge window [1]. It includes the per-inode DAX support, which was dependant on the DAX infrastructure which came in via the XFS tree, and a number of regression and bug fixes; most notably the "BUG: using smp_processor_id() in preemptible code in ext4_mb_new_blocks" reported by syzkaller" [1] The pull request actually came in 15 minutes after I had tagged the rc1 release. Tssk, tssk, late.. - Linus * tag 'ext4-for-linus-5.8-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: ext4, jbd2: ensure panic by fix a race between jbd2 abort and ext4 error handlers ext4: support xattr gnu.* namespace for the Hurd ext4: mballoc: Use this_cpu_read instead of this_cpu_ptr ext4: avoid utf8_strncasecmp() with unstable name ext4: stop overwrite the errcode in ext4_setup_super ext4: fix partial cluster initialization when splitting extent ext4: avoid race conditions when remounting with options that change dax Documentation/dax: Update DAX enablement for ext4 fs/ext4: Introduce DAX inode flag fs/ext4: Remove jflag variable fs/ext4: Make DAX mount option a tri-state fs/ext4: Only change S_DAX on inode load fs/ext4: Update ext4_should_use_dax() fs/ext4: Change EXT4_MOUNT_DAX to EXT4_MOUNT_DAX_ALWAYS fs/ext4: Disallow verity if inode is DAX fs/ext4: Narrow scope of DAX check in setflags
2020-06-03Merge tag 'vfs-5.8-merge-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linuxLinus Torvalds1-3/+139
Pull DAX updates part one from Darrick Wong: "After many years of LKML-wrangling about how to enable programs to query and influence the file data access mode (DAX) when a filesystem resides on storage devices such as persistent memory, Ira Weiny has emerged with a proposed set of standard behaviors that has not been shot down by anyone! We're more or less standardizing on the current XFS behavior and adapting ext4 to do the same. This is the first of a handful pull requests that will make ext4 and XFS present a consistent interface for user programs that care about DAX. We add a statx attribute that programs can check to see if DAX is enabled on a particular file. Then, we update the DAX documentation to spell out the user-visible behaviors that filesystems will guarantee (until the next storage industry shakeup). The on-disk inode flag has been in XFS for a few years now. Summary: - Clean up io_is_direct. - Add a new statx flag to indicate when file data access is being done via DAX (as opposed to the page cache). - Update the documentation for how system administrators and application programmers can take advantage of the (still experimental DAX) feature" Link: https://lore.kernel.org/lkml/20200505002016.1085071-1-ira.weiny@intel.com/ * tag 'vfs-5.8-merge-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: Documentation/dax: Update Usage section fs/stat: Define DAX statx attribute fs: Remove unneeded IS_DAX() check in io_is_direct()
2020-05-29Documentation/dax: Update DAX enablement for ext4Ira Weiny1-3/+3
Update the document to reflect ext4 and xfs now behave the same. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Ira Weiny <ira.weiny@intel.com> Link: https://lore.kernel.org/r/20200528150003.828793-10-ira.weiny@intel.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2020-05-04Documentation/dax: Update Usage sectionIra Weiny1-3/+139
Update the Usage section to reflect the new individual dax selection functionality. Signed-off-by: Ira Weiny <ira.weiny@intel.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2020-04-21docs: filesystems: fix renamed referencesMauro Carvalho Chehab1-1/+1
Some filesystem references got broken by a previous patch series I submitted. Address those. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Acked-by: David Sterba <dsterba@suse.com> # fs/affs/Kconfig Link: https://lore.kernel.org/r/57318c53008dbda7f6f4a5a9e5787f4d37e8565a.1586881715.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-07-15Documentation: filesystem: Convert xfs.txt to ReSTSheriff Esseson1-1/+1
Move xfs.txt to admin-guide, convert xfs.txt to ReST and broken references Signed-off-by: Sheriff Esseson <sheriffesseson@gmail.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2019-01-03doc: filesystems: fix bad references to nonexistent ext4.rst fileOtto Sabart1-1/+1
The ext4.rst file does not exist anymore. This patch changes all references to point to the whole ext4 directory. Fixes: d3091215921b ("docs: move ext4 administrative docs to admin-guide/") Signed-off-by: Otto Sabart <ottosabart@seberm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-09-20docs: fix some broken documentation referencesMauro Carvalho Chehab1-1/+1
Some documentation files received recent changes and are pointing to wrong places. Those references can easily fixed with the help of a script: $ ./scripts/documentation-file-ref-check --fix Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-01-28powerpc/cell: Remove axonram driverMichael Ellerman1-1/+0
The QS21/22 IBM Cell blades had a southbridge chip called Axon. This could have DDR DIMMs attached to it, though they were not directly usable as RAM, instead they could be used as some sort of buffer, if applications were written specifically to use the block device provided by the driver. Although the driver supposedly had direct access support, it was apparently never tested (see commit 91117a20245b ("axonram: Fix bug in direct_access")). These machines have not been available for over 5 years, and were never widely in use. It seems highly unlikely anyone is using this driver. In general we're happy to leave old drivers in the tree, but because DAX is involved this driver is caught up in the ongoing work in that area, but none of the DAX folks are able to test it. So remove the driver, if any one *is* using it, we'll be happy to put it back. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-09-07dax: use common 4k zero page for dax mmap readsRoss Zwisler1-3/+2
When servicing mmap() reads from file holes the current DAX code allocates a page cache page of all zeroes and places the struct page pointer in the mapping->page_tree radix tree. This has three major drawbacks: 1) It consumes memory unnecessarily. For every 4k page that is read via a DAX mmap() over a hole, we allocate a new page cache page. This means that if you read 1GiB worth of pages, you end up using 1GiB of zeroed memory. This is easily visible by looking at the overall memory consumption of the system or by looking at /proc/[pid]/smaps: 7f62e72b3000-7f63272b3000 rw-s 00000000 103:00 12 /root/dax/data Size: 1048576 kB Rss: 1048576 kB Pss: 1048576 kB Shared_Clean: 0 kB Shared_Dirty: 0 kB Private_Clean: 1048576 kB Private_Dirty: 0 kB Referenced: 1048576 kB Anonymous: 0 kB LazyFree: 0 kB AnonHugePages: 0 kB ShmemPmdMapped: 0 kB Shared_Hugetlb: 0 kB Private_Hugetlb: 0 kB Swap: 0 kB SwapPss: 0 kB KernelPageSize: 4 kB MMUPageSize: 4 kB Locked: 0 kB 2) It is slower than using a common zero page because each page fault has more work to do. Instead of just inserting a common zero page we have to allocate a page cache page, zero it, and then insert it. Here are the average latencies of dax_load_hole() as measured by ftrace on a random test box: Old method, using zeroed page cache pages: 3.4 us New method, using the common 4k zero page: 0.8 us This was the average latency over 1 GiB of sequential reads done by this simple fio script: [global] size=1G filename=/root/dax/data fallocate=none [io] rw=read ioengine=mmap 3) The fact that we had to check for both DAX exceptional entries and for page cache pages in the radix tree made the DAX code more complex. Solve these issues by following the lead of the DAX PMD code and using a common 4k zero page instead. As with the PMD code we will now insert a DAX exceptional entry into the radix tree instead of a struct page pointer which allows us to remove all the special casing in the DAX code. Note that we do still pretty aggressively check for regular pages in the DAX radix tree, especially where we take action based on the bits set in the page. If we ever find a regular page in our radix tree now that most likely means that someone besides DAX is inserting pages (which has happened lots of times in the past), and we want to find that out early and fail loudly. This solution also removes the extra memory consumption. Here is that same /proc/[pid]/smaps after 1GiB of reading from a hole with the new code: 7f2054a74000-7f2094a74000 rw-s 00000000 103:00 12 /root/dax/data Size: 1048576 kB Rss: 0 kB Pss: 0 kB Shared_Clean: 0 kB Shared_Dirty: 0 kB Private_Clean: 0 kB Private_Dirty: 0 kB Referenced: 0 kB Anonymous: 0 kB LazyFree: 0 kB AnonHugePages: 0 kB ShmemPmdMapped: 0 kB Shared_Hugetlb: 0 kB Private_Hugetlb: 0 kB Swap: 0 kB SwapPss: 0 kB KernelPageSize: 4 kB MMUPageSize: 4 kB Locked: 0 kB Overall system memory consumption is similarly improved. Another major change is that we remove dax_pfn_mkwrite() from our fault flow, and instead rely on the page fault itself to make the PTE dirty and writeable. The following description from the patch adding the vm_insert_mixed_mkwrite() call explains this a little more: "To be able to use the common 4k zero page in DAX we need to have our PTE fault path look more like our PMD fault path where a PTE entry can be marked as dirty and writeable as it is first inserted rather than waiting for a follow-up dax_pfn_mkwrite() => finish_mkwrite_fault() call. Right now we can rely on having a dax_pfn_mkwrite() call because we can distinguish between these two cases in do_wp_page(): case 1: 4k zero page => writable DAX storage case 2: read-only DAX storage => writeable DAX storage This distinction is made by via vm_normal_page(). vm_normal_page() returns false for the common 4k zero page, though, just as it does for DAX ptes. Instead of special casing the DAX + 4k zero page case we will simplify our DAX PTE page fault sequence so that it matches our DAX PMD sequence, and get rid of the dax_pfn_mkwrite() helper. We will instead use dax_iomap_fault() to handle write-protection faults. This means that insert_pfn() needs to follow the lead of insert_pfn_pmd() and allow us to pass in a 'mkwrite' flag. If 'mkwrite' is set insert_pfn() will do the work that was previously done by wp_page_reuse() as part of the dax_pfn_mkwrite() call path" Link: http://lkml.kernel.org/r/20170724170616.25810-4-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-11-21dax: rip out get_block based IO supportJan Kara1-11/+11
No one uses functions using the get_block callback anymore. Rip them out and update documentation. Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2016-10-01dax : Fix documentation with respect to struct pagesStephen Bates1-6/+9
The documentation for dax is not up to date with respect to the struct page support available in some of the device drivers that utilize it. Signed-off-by: Stephen Bates <sbates@raithlin.com> Acked-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2016-07-27dax: some small updates to dax.txt documentationRoss Zwisler1-2/+4
These are originally from Matthew Wilcox and were part of his huge "mm,fs,dax: Change ->pmd_fault to ->huge_fault" patch that was part of PUD support. I'm breaking these small changes out as they stand on their own and add useful information to Documentation/filesystems/dax.txt. Link: http://lkml.kernel.org/r/20160714214049.20075-1-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.com> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-18dax: for truncate/hole-punch, do zeroing through the driver if possibleVishal Verma1-0/+32
In the truncate or hole-punch path in dax, we clear out sub-page ranges. If these sub-page ranges are sector aligned and sized, we can do the zeroing through the driver instead so that error-clearing is handled automatically. For sub-sector ranges, we still have to rely on clear_pmem and have the possibility of tripping over errors. Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
2015-09-09dax: add huge page fault supportMatthew Wilcox1-3/+4
This is the support code for DAX-enabled filesystems to allow them to provide huge pages in response to faults. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Cc: Hillf Danton <dhillf@gmail.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-07-04dax: Add block size note to documentationMatthew Wilcox1-2/+4
For block devices which are small enough, mkfs will default to creating a filesystem with block sizes smaller than page size. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-02-17dax: does not work correctly with virtual aliasing cachesMatthew Wilcox1-0/+3
The DAX code accesses the underlying storage through the kernel's linear mapping, which may not be cache-coherent with user mappings on ARM, MIPS or SPARC. Temporarily disable the DAX code until this problem is resolved. The original XIP code also had this problem, but it was never noticed. Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com> Cc: Andreas Dilger <andreas.dilger@intel.com> Cc: Boaz Harrosh <boaz@plexistor.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-17ext4: add DAX functionalityRoss Zwisler1-0/+1
This is a port of the DAX functionality found in the current version of ext2. [matthew.r.wilcox@intel.com: heavily tweaked] [akpm@linux-foundation.org: remap_pages went away] Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com> Cc: Boaz Harrosh <boaz@plexistor.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-17dax: add dax_zero_page_rangeMatthew Wilcox1-0/+1
This new function allows us to support hole-punch for DAX files by zeroing a partial page, as opposed to the dax_truncate_page() function which can only truncate to the end of the page. Reimplement dax_truncate_page() to call dax_zero_page_range(). [ross.zwisler@linux.intel.com: ported to 3.13-rc2] [akpm@linux-foundation.org: fix typos in comments] Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Andreas Dilger <andreas.dilger@intel.com> Cc: Boaz Harrosh <boaz@plexistor.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-17dax: replace XIP documentation with DAX documentationMatthew Wilcox1-0/+89
Based on the original XIP documentation, this documents the current state of affairs, and includes instructions on how users can enable DAX if their devices and kernel support it. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Cc: Andreas Dilger <andreas.dilger@intel.com> Cc: Boaz Harrosh <boaz@plexistor.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>