lwn.git/mm/internal.h, branch docs-4.19

Merge tag 'xfs-4.18-merge-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

2018-06-05T20:24:20+00:00

Pull xfs updates from Darrick Wong: "New features this cycle include the ability to relabel mounted filesystems, support for fallocated swapfiles, and using FUA for pure data O_DSYNC directio writes. With this cycle we begin to integrate online filesystem repair and refactor the growfs code in preparation for eventual subvolume support, though the road ahead for both features is quite long. There are also numerous refactorings of the iomap code to remove unnecessary log overhead, to disentangle some of the quota code, and to prepare for buffer head removal in a future upstream kernel. Metadata validation continues to improve, both in the hot path veifiers and the online filesystem check code. I anticipate sending a second pull request in a few days with more metadata validation improvements. This series has been run through a full xfstests run over the weekend and through a quick xfstests run against this morning's master, with no major failures reported. Summary: - Strengthen inode number and structure validation when allocating inodes. - Reduce pointless buffer allocations during cache miss - Use FUA for pure data O_DSYNC directio writes - Various iomap refactorings - Strengthen quota metadata verification to avoid unfixable broken quota - Make AGFL block freeing a deferred operation to avoid blowing out transaction reservations when running complex operations - Get rid of the log item descriptors to reduce log overhead - Fix various reflink bugs where inodes were double-joined to transactions - Don't issue discards when trimming unwritten extents - Refactor incore dquot initialization and retrieval interfaces - Fix some locking problmes in the quota scrub code - Strengthen btree structure checks in scrub code - Rewrite swapfile activation to use iomap and support unwritten extents - Make scrub exit to userspace sooner when corruptions or cross-referencing problems are found - Make scrub invoke the data fork scrubber directly on metadata inodes - Don't do background reclamation of post-eof and cow blocks when the fs is suspended - Fix secondary superblock buffer lifespan hinting - Refactor growfs to use table-dispatched functions instead of long stringy functions - Move growfs code to libxfs - Implement online fs label getting and setting - Introduce online filesystem repair (in a very limited capacity) - Fix unit conversion problems in the realtime freemap iteration functions - Various refactorings and cleanups in preparation to remove buffer heads in a future release - Reimplement the old bmap call with iomap - Remove direct buffer head accesses from seek hole/data - Various bug fixes" * tag 'xfs-4.18-merge-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (121 commits) fs: use ->is_partially_uptodate in page_cache_seek_hole_data fs: remove the buffer_unwritten check in page_seek_hole_data fs: move page_cache_seek_hole_data to iomap.c xfs: use iomap_bmap iomap: add an iomap-based bmap implementation iomap: add a iomap_sector helper iomap: use __bio_add_page in iomap_dio_zero iomap: move IOMAP_F_BOUNDARY to gfs2 iomap: fix the comment describing IOMAP_NOWAIT iomap: inline data should be an iomap type, not a flag mm: split ->readpages calls to avoid non-contiguous pages lists mm: return an unsigned int from __do_page_cache_readahead mm: give the 'ret' variable a better name __do_page_cache_readahead block: add a lower-level bio_add_page interface xfs: fix error handling in xfs_refcount_insert() xfs: fix xfs_rtalloc_rec units xfs: strengthen rtalloc query range checks xfs: xfs_rtbuf_get should check the bmapi_read results xfs: xfs_rtword_t should be unsigned, not signed dax: change bdev_dax_supported() to support boolean returns ...

mm: return an unsigned int from __do_page_cache_readahead

2018-06-02T01:37:32+00:00

We never return an error, so switch to returning an unsigned int. Most callers already did implicit casts to an unsigned type, and the one that didn't can be simplified now. Suggested-by: Matthew Wilcox Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong

Revert "mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE"

2018-05-24T17:07:50+00:00

This reverts the following commits that change CMA design in MM. 3d2054ad8c2d ("ARM: CMA: avoid double mapping to the CMA area if CONFIG_HIGHMEM=y") 1d47a3ec09b5 ("mm/cma: remove ALLOC_CMA") bad8c6c0b114 ("mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE") Ville reported a following error on i386. Inode-cache hash table entries: 65536 (order: 6, 262144 bytes) microcode: microcode updated early to revision 0x4, date = 2013-06-28 Initializing CPU#0 Initializing HighMem for node 0 (000377fe:00118000) Initializing Movable for node 0 (00000001:00118000) BUG: Bad page state in process swapper pfn:377fe page:f53effc0 count:0 mapcount:-127 mapping:00000000 index:0x0 flags: 0x80000000() raw: 80000000 00000000 00000000 ffffff80 00000000 00000100 00000200 00000001 page dumped because: nonzero mapcount Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 4.17.0-rc5-elk+ #145 Hardware name: Dell Inc. Latitude E5410/03VXMC, BIOS A15 07/11/2013 Call Trace: dump_stack+0x60/0x96 bad_page+0x9a/0x100 free_pages_check_bad+0x3f/0x60 free_pcppages_bulk+0x29d/0x5b0 free_unref_page_commit+0x84/0xb0 free_unref_page+0x3e/0x70 __free_pages+0x1d/0x20 free_highmem_page+0x19/0x40 add_highpages_with_active_regions+0xab/0xeb set_highmem_pages_init+0x66/0x73 mem_init+0x1b/0x1d7 start_kernel+0x17a/0x363 i386_start_kernel+0x95/0x99 startup_32_smp+0x164/0x168 The reason for this error is that the span of MOVABLE_ZONE is extended to whole node span for future CMA initialization, and, normal memory is wrongly freed here. I submitted the fix and it seems to work, but, another problem happened. It's so late time to fix the later problem so I decide to reverting the series. Reported-by: Ville Syrjälä Acked-by: Laura Abbott Acked-by: Michal Hocko Cc: Andrew Morton Signed-off-by: Joonsoo Kim Signed-off-by: Linus Torvalds

mm/cma: remove ALLOC_CMA

2018-04-11T17:28:32+00:00

Now, all reserved pages for CMA region are belong to the ZONE_MOVABLE and it only serves for a request with GFP_HIGHMEM && GFP_MOVABLE. Therefore, we don't need to maintain ALLOC_CMA at all. Link: http://lkml.kernel.org/r/1512114786-5085-3-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim Reviewed-by: Aneesh Kumar K.V Tested-by: Tony Lindgren Acked-by: Vlastimil Babka Cc: Johannes Weiner Cc: Laura Abbott Cc: Marek Szyprowski Cc: Mel Gorman Cc: Michal Hocko Cc: Michal Nazarewicz Cc: Minchan Kim Cc: Rik van Riel Cc: Russell King Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE

2018-04-11T17:28:32+00:00

Patch series "mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE", v2. 0. History This patchset is the follow-up of the discussion about the "Introduce ZONE_CMA (v7)" [1]. Please reference it if more information is needed. 1. What does this patch do? This patch changes the management way for the memory of the CMA area in the MM subsystem. Currently the memory of the CMA area is managed by the zone where their pfn is belong to. However, this approach has some problems since MM subsystem doesn't have enough logic to handle the situation that different characteristic memories are in a single zone. To solve this issue, this patch try to manage all the memory of the CMA area by using the MOVABLE zone. In MM subsystem's point of view, characteristic of the memory on the MOVABLE zone and the memory of the CMA area are the same. So, managing the memory of the CMA area by using the MOVABLE zone will not have any problem. 2. Motivation There are some problems with current approach. See following. Although these problem would not be inherent and it could be fixed without this conception change, it requires many hooks addition in various code path and it would be intrusive to core MM and would be really error-prone. Therefore, I try to solve them with this new approach. Anyway, following is the problems of the current implementation. o CMA memory utilization First, following is the freepage calculation logic in MM. - For movable allocation: freepage = total freepage - For unmovable allocation: freepage = total freepage - CMA freepage Freepages on the CMA area is used after the normal freepages in the zone where the memory of the CMA area is belong to are exhausted. At that moment that the number of the normal freepages is zero, so - For movable allocation: freepage = total freepage = CMA freepage - For unmovable allocation: freepage = 0 If unmovable allocation comes at this moment, allocation request would fail to pass the watermark check and reclaim is started. After reclaim, there would exist the normal freepages so freepages on the CMA areas would not be used. FYI, there is another attempt [2] trying to solve this problem in lkml. And, as far as I know, Qualcomm also has out-of-tree solution for this problem. Useless reclaim: There is no logic to distinguish CMA pages in the reclaim path. Hence, CMA page is reclaimed even if the system just needs the page that can be usable for the kernel allocation. Atomic allocation failure: This is also related to the fallback allocation policy for the memory of the CMA area. Consider the situation that the number of the normal freepages is *zero* since the bunch of the movable allocation requests come. Kswapd would not be woken up due to following freepage calculation logic. - For movable allocation: freepage = total freepage = CMA freepage If atomic unmovable allocation request comes at this moment, it would fails due to following logic. - For unmovable allocation: freepage = total freepage - CMA freepage = 0 It was reported by Aneesh [3]. Useless compaction: Usual high-order allocation request is unmovable allocation request and it cannot be served from the memory of the CMA area. In compaction, migration scanner try to migrate the page in the CMA area and make high-order page there. As mentioned above, it cannot be usable for the unmovable allocation request so it's just waste. 3. Current approach and new approach Current approach is that the memory of the CMA area is managed by the zone where their pfn is belong to. However, these memory should be distinguishable since they have a strong limitation. So, they are marked as MIGRATE_CMA in pageblock flag and handled specially. However, as mentioned in section 2, the MM subsystem doesn't have enough logic to deal with this special pageblock so many problems raised. New approach is that the memory of the CMA area is managed by the MOVABLE zone. MM already have enough logic to deal with special zone like as HIGHMEM and MOVABLE zone. So, managing the memory of the CMA area by the MOVABLE zone just naturally work well because constraints for the memory of the CMA area that the memory should always be migratable is the same with the constraint for the MOVABLE zone. There is one side-effect for the usability of the memory of the CMA area. The use of MOVABLE zone is only allowed for a request with GFP_HIGHMEM && GFP_MOVABLE so now the memory of the CMA area is also only allowed for this gfp flag. Before this patchset, a request with GFP_MOVABLE can use them. IMO, It would not be a big issue since most of GFP_MOVABLE request also has GFP_HIGHMEM flag. For example, file cache page and anonymous page. However, file cache page for blockdev file is an exception. Request for it has no GFP_HIGHMEM flag. There is pros and cons on this exception. In my experience, blockdev file cache pages are one of the top reason that causes cma_alloc() to fail temporarily. So, we can get more guarantee of cma_alloc() success by discarding this case. Note that there is no change in admin POV since this patchset is just for internal implementation change in MM subsystem. Just one minor difference for admin is that the memory stat for CMA area will be printed in the MOVABLE zone. That's all. 4. Result Following is the experimental result related to utilization problem. 8 CPUs, 1024 MB, VIRTUAL MACHINE make -j16 CMA area: 0 MB 512 MB Elapsed-time: 92.4 186.5 pswpin: 82 18647 pswpout: 160 69839 CMA : 0 MB 512 MB Elapsed-time: 93.1 93.4 pswpin: 84 46 pswpout: 183 92 akpm: "kernel test robot" reported a 26% improvement in vm-scalability.throughput: http://lkml.kernel.org/r/20180330012721.GA3845@yexl-desktop [1]: lkml.kernel.org/r/1491880640-9944-1-git-send-email-iamjoonsoo.kim@lge.com [2]: https://lkml.org/lkml/2014/10/15/623 [3]: http://www.spinics.net/lists/linux-mm/msg100562.html Link: http://lkml.kernel.org/r/1512114786-5085-2-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim Reviewed-by: Aneesh Kumar K.V Tested-by: Tony Lindgren Acked-by: Vlastimil Babka Cc: Johannes Weiner Cc: Laura Abbott Cc: Marek Szyprowski Cc: Mel Gorman Cc: Michal Hocko Cc: Michal Nazarewicz Cc: Minchan Kim Cc: Rik van Riel Cc: Russell King Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, migrate: remove reason argument from new_page_t

2018-04-11T17:28:32+00:00

No allocation callback is using this argument anymore. new_page_node used to use this parameter to convey node_id resp. migration error up to move_pages code (do_move_page_to_node_array). The error status never made it into the final status field and we have a better way to communicate node id to the status field now. All other allocation callbacks simply ignored the argument so we can drop it finally. [mhocko@suse.com: fix migration callback] Link: http://lkml.kernel.org/r/20180105085259.GH2801@dhcp22.suse.cz [akpm@linux-foundation.org: fix alloc_misplaced_dst_page()] [mhocko@kernel.org: fix build] Link: http://lkml.kernel.org/r/20180103091134.GB11319@dhcp22.suse.cz Link: http://lkml.kernel.org/r/20180103082555.14592-3-mhocko@kernel.org Signed-off-by: Michal Hocko Reviewed-by: Zi Yan Cc: Andrea Reale Cc: Anshuman Khandual Cc: Kirill A. Shutemov Cc: Mike Kravetz Cc: Naoya Horiguchi Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, numa: rework do_pages_move

2018-04-11T17:28:32+00:00

Patch series "unclutter thp migration" Motivation: THP migration is hacked into the generic migration with rather surprising semantic. The migration allocation callback is supposed to check whether the THP can be migrated at once and if that is not the case then it allocates a simple page to migrate. unmap_and_move then fixes that up by splitting the THP into small pages while moving the head page to the newly allocated order-0 page. Remaining pages are moved to the LRU list by split_huge_page. The same happens if the THP allocation fails. This is really ugly and error prone [2]. I also believe that split_huge_page to the LRU lists is inherently wrong because all tail pages are not migrated. Some callers will just work around that by retrying (e.g. memory hotplug). There are other pfn walkers which are simply broken though. e.g. madvise_inject_error will migrate head and then advances next pfn by the huge page size. do_move_page_to_node_array, queue_pages_range (migrate_pages, mbind), will simply split the THP before migration if the THP migration is not supported then falls back to single page migration but it doesn't handle tail pages if the THP migration path is not able to allocate a fresh THP so we end up with ENOMEM and fail the whole migration which is a questionable behavior. Page compaction doesn't try to migrate large pages so it should be immune. The first patch reworks do_pages_move which relies on a very ugly calling semantic when the return status is pushed to the migration path via private pointer. It uses pre allocated fixed size batching to achieve that. We simply cannot do the same if a THP is to be split during the migration path which is done in the patch 3. Patch 2 is follow up cleanup which removes the mentioned return status calling convention ugliness. On a side note: There are some semantic issues I have encountered on the way when working on patch 1 but I am not addressing them here. E.g. trying to move THP tail pages will result in either success or EBUSY (the later one more likely once we isolate head from the LRU list). Hugetlb reports EACCESS on tail pages. Some errors are reported via status parameter but migration failures are not even though the original `reason' argument suggests there was an intention to do so. From a quick look into git history this never worked. I have tried to keep the semantic unchanged. Then there is a relatively minor thing that the page isolation might fail because of pages not being on the LRU - e.g. because they are sitting on the per-cpu LRU caches. Easily fixable. This patch (of 3): do_pages_move is supposed to move user defined memory (an array of addresses) to the user defined numa nodes (an array of nodes one for each address). The user provided status array then contains resulting numa node for each address or an error. The semantic of this function is little bit confusing because only some errors are reported back. Notably migrate_pages error is only reported via the return value. This patch doesn't try to address these semantic nuances but rather change the underlying implementation. Currently we are processing user input (which can be really large) in batches which are stored to a temporarily allocated page. Each address is resolved to its struct page and stored to page_to_node structure along with the requested target numa node. The array of these structures is then conveyed down the page migration path via private argument. new_page_node then finds the corresponding structure and allocates the proper target page. What is the problem with the current implementation and why to change it? Apart from being quite ugly it also doesn't cope with unexpected pages showing up on the migration list inside migrate_pages path. That doesn't happen currently but the follow up patch would like to make the thp migration code more clear and that would need to split a THP into the list for some cases. How does the new implementation work? Well, instead of batching into a fixed size array we simply batch all pages that should be migrated to the same node and isolate all of them into a linked list which doesn't require any additional storage. This should work reasonably well because page migration usually migrates larger ranges of memory to a specific node. So the common case should work equally well as the current implementation. Even if somebody constructs an input where the target numa nodes would be interleaved we shouldn't see a large performance impact because page migration alone doesn't really benefit from batching. mmap_sem batching for the lookup is quite questionable and isolate_lru_page which would benefit from batching is not using it even in the current implementation. Link: http://lkml.kernel.org/r/20180103082555.14592-2-mhocko@kernel.org Signed-off-by: Michal Hocko Acked-by: Kirill A. Shutemov Reviewed-by: Andrew Morton Cc: Anshuman Khandual Cc: Zi Yan Cc: Naoya Horiguchi Cc: Vlastimil Babka Cc: Andrea Reale Cc: Kirill A. Shutemov Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Revert "mm, thp: Do not make pmd/pud dirty without a reason"

2017-11-29T17:01:01+00:00

This reverts commit 152e93af3cfe2d29d8136cc0a02a8612507136ee. It was a nice cleanup in theory, but as Nicolai Stange points out, we do need to make the page dirty for the copy-on-write case even when we didn't end up making it writable, since the dirty bit is what we use to check that we've gone through a COW cycle. Reported-by: Michal Hocko Acked-by: Kirill A. Shutemov Signed-off-by: Linus Torvalds

mm, thp: Do not make pmd/pud dirty without a reason

2017-11-27T20:26:29+00:00

Currently we make page table entries dirty all the time regardless of access type and don't even consider if the mapping is write-protected. The reasoning is that we don't really need dirty tracking on THP and making the entry dirty upfront may save some time on first write to the page. Unfortunately, such approach may result in false-positive can_follow_write_pmd() for huge zero page or read-only shmem file. Let's only make page dirty only if we about to write to the page anyway (as we do for small pages). I've restructured the code to make entry dirty inside maybe_p[mu]d_mkwrite(). It also takes into account if the vma is write-protected. Signed-off-by: Kirill A. Shutemov Acked-by: Michal Hocko Cc: Hugh Dickins Signed-off-by: Linus Torvalds

mm, compaction: split off flag for not updating skip hints

2017-11-18T00:10:00+00:00

Pageblock skip hints were added as a heuristic for compaction, which shares core code with CMA. Since CMA reliability would suffer from the heuristics, compact_control flag ignore_skip_hint was added for the CMA use case. Since 6815bf3f233e ("mm/compaction: respect ignore_skip_hint in update_pageblock_skip") the flag also means that CMA won't *update* the skip hints in addition to ignoring them. Today, direct compaction can also ignore the skip hints in the last resort attempt, but there's no reason not to set them when isolation fails in such case. Thus, this patch splits off a new no_set_skip_hint flag to avoid the updating, which only CMA sets. This should improve the heuristics a bit, and allow us to simplify the persistent skip bit handling as the next step. Link: http://lkml.kernel.org/r/20171102121706.21504-2-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Mel Gorman Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds