- 18 Apr, 2023 40 commits
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David Hildenbrand authored
Let's add some tests that trigger (pte|pmd)_mkdirty on VMAs without write permissions. If an architecture implementation is wrong, we might accidentally set the PTE/PMD writable and allow for write access in a VMA without write permissions. The tests include reproducers for the two issues recently discovered and worked-around in core-MM for now: (1) commit 624a2c94 ("Partly revert "mm/thp: carry over dirty bit when thp splits on pmd"") (2) commit 96a9c287 ("mm/migrate: fix wrongly apply write bit after mkdirty on sparc64") In addition, some other tests that reveal further issues. All tests pass under x86_64: ./mkdirty # [INFO] detected THP size: 2048 KiB TAP version 13 1..6 # [INFO] PTRACE write access ok 1 SIGSEGV generated, page not modified # [INFO] PTRACE write access to THP ok 2 SIGSEGV generated, page not modified # [INFO] Page migration ok 3 SIGSEGV generated, page not modified # [INFO] Page migration of THP ok 4 SIGSEGV generated, page not modified # [INFO] PTE-mapping a THP ok 5 SIGSEGV generated, page not modified # [INFO] UFFDIO_COPY ok 6 SIGSEGV generated, page not modified # Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0 But some fail on sparc64: ./mkdirty # [INFO] detected THP size: 8192 KiB TAP version 13 1..6 # [INFO] PTRACE write access not ok 1 SIGSEGV generated, page not modified # [INFO] PTRACE write access to THP not ok 2 SIGSEGV generated, page not modified # [INFO] Page migration ok 3 SIGSEGV generated, page not modified # [INFO] Page migration of THP ok 4 SIGSEGV generated, page not modified # [INFO] PTE-mapping a THP ok 5 SIGSEGV generated, page not modified # [INFO] UFFDIO_COPY not ok 6 SIGSEGV generated, page not modified Bail out! 3 out of 6 tests failed # Totals: pass:3 fail:3 xfail:0 xpass:0 skip:0 error:0 Reverting both above commits makes all tests fail on sparc64: ./mkdirty # [INFO] detected THP size: 8192 KiB TAP version 13 1..6 # [INFO] PTRACE write access not ok 1 SIGSEGV generated, page not modified # [INFO] PTRACE write access to THP not ok 2 SIGSEGV generated, page not modified # [INFO] Page migration not ok 3 SIGSEGV generated, page not modified # [INFO] Page migration of THP not ok 4 SIGSEGV generated, page not modified # [INFO] PTE-mapping a THP not ok 5 SIGSEGV generated, page not modified # [INFO] UFFDIO_COPY not ok 6 SIGSEGV generated, page not modified Bail out! 6 out of 6 tests failed # Totals: pass:0 fail:6 xfail:0 xpass:0 skip:0 error:0 The tests are useful to detect other problematic archs, to verify new arch fixes, and to stop such issues from reappearing in the future. For now, we don't add any hugetlb tests. Link: https://lkml.kernel.org/r/20230411142512.438404-3-david@redhat.comSigned-off-by:
David Hildenbrand <david@redhat.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: David S. Miller <davem@davemloft.net> Cc: Hugh Dickins <hughd@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Yu Zhao <yuzhao@google.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org>
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David Hildenbrand authored
Patch series "mm: (pte|pmd)_mkdirty() should not unconditionally allow for write access". This is the follow-up on [1], adding selftests (testing for known issues we added workarounds for and other issues that haven't been fixed yet), fixing sparc64, reverting the workarounds, and perform one cleanup. The patch from [1] was modified slightly (updated/extended patch description, dropped one unnecessary NOP instruction from the ASM in __pte_mkhwwrite()). Retested on x86_64 and sparc64 (sun4u in QEMU). I scanned most architectures to make sure their (pte|pmd)_mkdirty() handling is correct. To be sure, we can run the selftests and find out if other architectures are still affectes (loongarch was fixed recently as well). Based on master for now. I don't expect surprises regarding mm-tress, but I can rebase if there are any problems. This patch (of 6): The COW selftest can deal with THP not being configured. So move error handling of read_pmd_pagesize() into the callers such that we can reuse it in the COW selftest. Link: https://lkml.kernel.org/r/20230411142512.438404-1-david@redhat.com Link: https://lkml.kernel.org/r/20221212130213.136267-1-david@redhat.com [1] Link: https://lkml.kernel.org/r/20230411142512.438404-2-david@redhat.comSigned-off-by:
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Christoph Hellwig authored
Propagate read errors to the caller instead of dropping them on the floor, and stop returning the somewhat dangerous 1 on success from read_from_bdev*. Link: https://lkml.kernel.org/r/20230411171459.567614-18-hch@lst.deSigned-off-by:
Christoph Hellwig <hch@lst.de> Reviewed-by:
Sergey Senozhatsky <senozhatsky@chromium.org> Acked-by:
Minchan Kim <minchan@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by:
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Christoph Hellwig authored
Currently nothing waits for the synchronous reads before accessing the data. Switch them to an on-stack bio and submit_bio_wait to make sure the I/O has actually completed when the work item has been flushed. This also removes the call to page_endio that would unlock a page that has never been locked. Drop the partial_io/sync flag, as chaining only makes sense for the asynchronous reads of the entire page. Link: https://lkml.kernel.org/r/20230411171459.567614-17-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
bio_alloc will never return a NULL bio when it is allowed to sleep, and adding a single page to bio with a single vector also can't fail, so switch to the asserting __bio_add_page variant and drop the error returns. Link: https://lkml.kernel.org/r/20230411171459.567614-16-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
read_from_bdev always reads a whole page, so pass a page to it instead of the bvec and remove the now pointless zram_bvec_read_from_bdev wrapper. Link: https://lkml.kernel.org/r/20230411171459.567614-15-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Split the read/modify/write case into a separate helper. Link: https://lkml.kernel.org/r/20230411171459.567614-14-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
__zram_bvec_write only extracts the page from __zram_bvec_write and always expects a full page of input. Pass the page directly instead of the bvec and rename the function to zram_write_page. Link: https://lkml.kernel.org/r/20230411171459.567614-13-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Split the partial read into a separate helper. Link: https://lkml.kernel.org/r/20230411171459.567614-12-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
writeback_store always reads a full page, so just call zram_read_page directly and bypass the boune buffer handling. Link: https://lkml.kernel.org/r/20230411171459.567614-11-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
__zram_bvec_read doesn't get passed a bvec, but always read a whole page. Rename it to make the usage more clear. Link: https://lkml.kernel.org/r/20230411171459.567614-10-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
There is no point in allocation a highmem page when we instantly need to copy from it. Link: https://lkml.kernel.org/r/20230411171459.567614-9-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Instead of having an outer loop in __zram_make_request and then branch out for reads vs writes for each loop iteration in zram_bvec_rw, split the main handler into separat zram_bio_read and zram_bio_write handlers that also include the functionality formerly in zram_bvec_rw. Link: https://lkml.kernel.org/r/20230411171459.567614-8-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
When the low-level access fails, don't clear the idle flag or clear the caches, and just return. Link: https://lkml.kernel.org/r/20230411171459.567614-7-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Switch on the bio operation in zram_submit_bio and only call into __zram_make_request for read and write operations. Link: https://lkml.kernel.org/r/20230411171459.567614-6-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
bio_for_each_segment synthetize bvecs that never cross page boundaries, so don't duplicate that work in an inner loop. Link: https://lkml.kernel.org/r/20230411171459.567614-5-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Derive the index and offset variables inside the function, and complete the bio directly in preparation for cleaning up the I/O path. Link: https://lkml.kernel.org/r/20230411171459.567614-4-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
All bios hande to drivers from the block layer are checked against the device size and for logical block alignment already (and have been since long before zram was merged), so don't duplicate those checks. Link: https://lkml.kernel.org/r/20230411171459.567614-3-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Patch series "zram I/O path cleanups and fixups", v3. This series cleans up the zram I/O path, and fixes the handling of synchronous I/O to the underlying device in the writeback_store function or for > 4K PAGE_SIZE systems. The fixes are at the end, as I could not fully reason about them being safe before untangling the callchain. This patch (of 17): read_from_bdev_sync is currently only compiled for non-4k PAGE_SIZE, which means it won't be built with the most common configurations. Replace the ifdef with a check for the PAGE_SIZE in an if instead. The check uses an extra symbol and IS_ENABLED to allow the compiler to eliminate the dead code, leading to the same generated code size: text data bss dec hex filename 16709 1428 12 18149 46e5 drivers/block/zram/zram_drv.o.old 16709 1428 12 18149 46e5 drivers/block/zram/zram_drv.o.new Link: https://lkml.kernel.org/r/20230411171459.567614-1-hch@lst.de Link: https://lkml.kernel.org/r/20230411171459.567614-2-hch@lst.deSigned-off-by:
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Peng Zhang authored
Add a test case to check whether the number of maple_alloc structures is actually equal to mas->alloc->total. Link: https://lkml.kernel.org/r/20230411041005.26205-2-zhangpeng.00@bytedance.comSigned-off-by:
Peng Zhang <zhangpeng.00@bytedance.com> Cc: Liam R. Howlett <Liam.Howlett@Oracle.com> Signed-off-by:
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Tom Rix authored
smatch reports mm/backing-dev.c:266:1: warning: symbol 'dev_attr_min_bytes' was not declared. Should it be static? mm/backing-dev.c:294:1: warning: symbol 'dev_attr_max_bytes' was not declared. Should it be static? These variables are only used in one file so should be static. Link: https://lkml.kernel.org/r/20230408141609.2703647-1-trix@redhat.comSigned-off-by:
Tom Rix <trix@redhat.com> Reviewed-by:
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Peng Zhang authored
The type of variable pointed to by pivs is unsigned long, but the type used in sizeof is a pointer type. Change it to unsigned long. This change has no runtime effect, as sizeof(ul) == sizeof(ul *). Link: https://lkml.kernel.org/r/20230411023513.15227-1-zhangpeng.00@bytedance.com Fixes: 54a611b6 ("Maple Tree: add new data structure") Signed-off-by:
David Binderman <dcb314@hotmail.com> Reviewed-by:
Liam R. Howlett <Liam.Howlett@oracle.com> Signed-off-by:
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ZhangPeng authored
Convert mfill_atomic_pte_copy(), shmem_mfill_atomic_pte() and mfill_atomic_pte() to take in a folio pointer. Convert mfill_atomic() to use a folio. Convert page_kaddr to kaddr in mfill_atomic(). Link: https://lkml.kernel.org/r/20230410133932.32288-7-zhangpeng362@huawei.comSigned-off-by:
ZhangPeng <zhangpeng362@huawei.com> Reviewed-by:
Mike Kravetz <mike.kravetz@oracle.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nanyong Sun <sunnanyong@huawei.com> Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com> Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com> Signed-off-by:
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ZhangPeng authored
Replace copy_user_huge_page() with copy_user_large_folio(). copy_user_large_folio() does the same as copy_user_huge_page(), but takes in folios instead of pages. Remove pages_per_huge_page from copy_user_large_folio(), because we can get that from folio_nr_pages(dst). Convert copy_user_gigantic_page() to take in folios. Link: https://lkml.kernel.org/r/20230410133932.32288-6-zhangpeng362@huawei.comSigned-off-by:
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ZhangPeng authored
Convert hugetlb_mfill_atomic_pte() to take in a folio pointer instead of a page pointer. Convert mfill_atomic_hugetlb() to use a folio. Link: https://lkml.kernel.org/r/20230410133932.32288-5-zhangpeng362@huawei.comSigned-off-by:
Sidhartha Kumar <sidhartha.kumar@oracle.com> Reviewed-by:
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ZhangPeng authored
Replace copy_huge_page_from_user() with copy_folio_from_user(). copy_folio_from_user() does the same as copy_huge_page_from_user(), but takes in a folio instead of a page. Convert page_kaddr to kaddr in copy_folio_from_user() to do indenting cleanup. Link: https://lkml.kernel.org/r/20230410133932.32288-4-zhangpeng362@huawei.comSigned-off-by:
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ZhangPeng authored
kmap() and kmap_atomic() are being deprecated in favor of kmap_local_page() which is appropriate for any thread local context.[1] Let's replace the kmap() and kmap_atomic() with kmap_local_page() in copy_huge_page_from_user(). When allow_pagefault is false, disable page faults to prevent potential deadlock.[2] [1] https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/ [2] https://lkml.kernel.org/r/20221025220136.2366143-1-ira.weiny@intel.com Link: https://lkml.kernel.org/r/20230410133932.32288-3-zhangpeng362@huawei.comSigned-off-by:
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ZhangPeng authored
Patch series "userfaultfd: convert userfaultfd functions to use folios", v6. This patch series converts several userfaultfd functions to use folios. This patch (of 6): Call vma_alloc_folio() directly instead of alloc_page_vma() and convert page_kaddr to kaddr in mfill_atomic_pte_copy(). Removes several calls to compound_head(). Link: https://lkml.kernel.org/r/20230410133932.32288-1-zhangpeng362@huawei.com Link: https://lkml.kernel.org/r/20230410133932.32288-2-zhangpeng362@huawei.comSigned-off-by:
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Steven Price authored
When !CONFIG_SHMEM smaps_shmem_walk_ops is defined but not used, triggering a compiler warning. To avoid the warning remove the #ifdef around the usage. This has no effect because shmem_mapping() is a stub returning false when !CONFIG_SHMEM so the code will be compiled out, however we now need to also provide a stub for shmem_swap_usage(). Link: https://lkml.kernel.org/r/20230405103819.151246-1-steven.price@arm.com Fixes: 7b86ac33 ("pagewalk: separate function pointers from iterator data") Signed-off-by:
Steven Price <steven.price@arm.com> Reported-by:
kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/oe-kbuild-all/202304031749.UiyJpxzF-lkp@intel.com/Reviewed-by:
Jason Gunthorpe <jgg@nvidia.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Signed-off-by:
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Vlastimil Babka authored
Commit 700d2e9a ("mm, page_alloc: reduce page alloc/free sanity checks") has introduced a new static key check_pages_enabled to control when struct pages are sanity checked during allocation and freeing. Mel Gorman suggested that free_tail_pages_check() could use this static key as well, instead of relying on CONFIG_DEBUG_VM. That makes sense, so do that. Also rename the function to free_tail_page_prepare() because it works on a single tail page and has a struct page preparation component as well as the optional checking component. Also remove some unnecessary unlikely() within static_branch_unlikely() statements that Mel pointed out for commit 700d2e9a. Link: https://lkml.kernel.org/r/20230405142840.11068-1-vbabka@suse.czSigned-off-by:
Vlastimil Babka <vbabka@suse.cz> Suggested-by:
Mel Gorman <mgorman@techsingularity.net> Acked-by:
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David Hildenbrand authored
If we end up with a writable migration entry that has the uffd-wp bit set, we already messed up: the source PTE/PMD was writable, which means we could have modified the page without notifying uffd first. Setting the uffd-wp bit always implies converting migration entries to !writable migration entries. Commit 8f34f1ea ("mm/userfaultfd: fix uffd-wp special cases for fork()") documents that "3. Forget to carry over uffd-wp bit for a write migration huge pmd entry", but it doesn't really say why that should be relevant. So let's remove that code to avoid hiding an eventual underlying issue (in the future, we might want to warn when creating writable migration entries that have the uffd-wp bit set -- or even better when turning a PTE writable that still has the uffd-wp bit set). This now matches the handling for hugetlb migration entries in hugetlb_change_protection(). In copy_huge_pmd()/copy_nonpresent_pte()/copy_hugetlb_page_range(), we still transfer the uffd-bit also for writable migration entries, but simply because we have unified handling for "writable" and "readable-exclusive" migration entries, and we care about transferring the uffd-wp bit for the latter. Link: https://lkml.kernel.org/r/20230405160236.587705-3-david@redhat.comSigned-off-by:
Peter Xu <peterx@redhat.com> Cc: Muhammad Usama Anjum <usama.anjum@collabora.com> Signed-off-by:
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Qi Zheng authored
Since we have updated mlock to use folios, it's better to call folios_put() instead of calling release_pages() directly. Link: https://lkml.kernel.org/r/20230405161854.6931-2-zhengqi.arch@bytedance.comSigned-off-by:
Qi Zheng <zhengqi.arch@bytedance.com> Acked-by:
Mel Gorman <mgorman@suse.de> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by:
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Josh Triplett authored
If a library wants to get information from auxv (for instance, AT_HWCAP/AT_HWCAP2), it has a few options, none of them perfectly reliable or ideal: - Be main or the pre-main startup code, and grub through the stack above main. Doesn't work for a library. - Call libc getauxval. Not ideal for libraries that are trying to be libc-independent and/or don't otherwise require anything from other libraries. - Open and read /proc/self/auxv. Doesn't work for libraries that may run in arbitrarily constrained environments that may not have /proc mounted (e.g. libraries that might be used by an init program or a container setup tool). - Assume you're on the main thread and still on the original stack, and try to walk the stack upwards, hoping to find auxv. Extremely bad idea. - Ask the caller to pass auxv in for you. Not ideal for a user-friendly library, and then your caller may have the same problem. Add a prctl that copies current->mm->saved_auxv to a userspace buffer. Link: https://lkml.kernel.org/r/d81864a7f7f43bca6afa2a09fc2e850e4050ab42.1680611394.git.josh@joshtriplett.orgSigned-off-by:
Josh Triplett <josh@joshtriplett.org> Signed-off-by:
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Peng Zhang authored
Simplify code of mas_wr_node_walk() without changing functionality, and improve readability. Remove some special judgments. Instead of dynamically recording the min and max in the loop, get the final min and max directly at the end. Link: https://lkml.kernel.org/r/20230314124203.91572-3-zhangpeng.00@bytedance.comSigned-off-by:
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David Hildenbrand authored
As noticed by Geert, commit b5c88f21 ("microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE") modified m68k code by accident. While replacing 0x080 by CF_PAGE_NOCACHE is correct, although it should have been part of commit ed415406 ("m68k/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE"), replacing "bit 7" by "bit 24" in the comment was wrong. Let's revert to the previous, correct, comment. Link: https://lkml.kernel.org/r/20230404085636.121409-1-david@redhat.comSigned-off-by:
Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by:
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ZhangPeng authored
Using vma_lookup() verifies the address is contained in the found vma. This results in easier to read the code. Link: https://lkml.kernel.org/r/20230404094515.1883552-1-zhangpeng362@huawei.comSigned-off-by:
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Florian Schmidt authored
cgroups v1 has a unique way of setting up memory pressure notifications: the user opens "memory.pressure_level" of the cgroup they want to monitor for pressure, then open "cgroup.event_control" and write the fd (among other things) to that file. memory.pressure_level has no other use, specifically it does not support any read or write operations. Consequently, no handlers are provided, and cgroup_file_mode() sets the permissions to 000. However, to actually use the mechanism, the subscribing user must have read access to the file and open the fd for reading, see memcg_write_event_control(). This is all fine as long as the subscribing process runs as root and is otherwise unconfined by further restrictions. However, if you add strict access controls such as selinux, the permission bits will be enforced, and opening memory.pressure_level for reading will fail, preventing the process from subscribing, even as root. To work around this issue, introduce a dummy read handler. When memory.pressure_level is created, cgroup_file_mode() will notice the existence of a handler, and therefore add read permissions to the file. Link: https://lkml.kernel.org/r/20230404105900.2005-1-flosch@nutanix.comSigned-off-by:
Florian Schmidt <flosch@nutanix.com> Acked-by:
Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Shakeel Butt <shakeelb@google.com> Signed-off-by:
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David Stevens authored
Make sure that collapse_file doesn't interfere with checking the uptodate flag in the page cache by only inserting hpage into the page cache after it has been updated and marked uptodate. This is achieved by simply not replacing present pages with hpage when iterating over the target range. The present pages are already locked, so replacing them with the locked hpage before the collapse is finalized is unnecessary. However, it is necessary to stop freezing the present pages after validating them, since leaving long-term frozen pages in the page cache can lead to deadlocks. Simply checking the reference count is sufficient to ensure that there are no long-term references hanging around that would the collapse would break. Similar to hpage, there is no reason that the present pages actually need to be frozen in addition to being locked. This fixes a race where folio_seek_hole_data would mistake hpage for an fallocated but unwritten page. This race is visible to userspace via data temporarily disappearing from SEEK_DATA/SEEK_HOLE. This also fixes a similar race where pages could temporarily disappear from mincore. Link: https://lkml.kernel.org/r/20230404120117.2562166-5-stevensd@google.com Fixes: f3f0e1d2 ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by:
David Stevens <stevensd@chromium.org> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jiaqi Yan <jiaqiyan@google.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Peter Xu <peterx@redhat.com> Cc: Yang Shi <shy828301@gmail.com> Signed-off-by:
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David Stevens authored
Make sure that collapse_file respects any userfaultfds registered with MODE_MISSING. If userspace has any such userfaultfds registered, then for any page which it knows to be missing, it may expect a UFFD_EVENT_PAGEFAULT. This means collapse_file needs to be careful when collapsing a shmem range would result in replacing an empty page with a THP, to avoid breaking userfaultfd. Synchronization when checking for userfaultfds in collapse_file is tricky because the mmap locks can't be used to prevent races with the registration of new userfaultfds. Instead, we provide synchronization by ensuring that userspace cannot observe the fact that pages are missing before we check for userfaultfds. Although this allows registration of a userfaultfd to race with collapse_file, it ensures that userspace cannot observe any pages transition from missing to present after such a race occurs. This makes such a race indistinguishable to the collapse occurring immediately before the userfaultfd registration. The first step to provide this synchronization is to stop filling gaps during the loop iterating over the target range, since the page cache lock can be dropped during that loop. The second step is to fill the gaps with XA_RETRY_ENTRY after the page cache lock is acquired the final time, to avoid races with accesses to the page cache that only take the RCU read lock. The fact that we don't fill holes during the initial iteration means that collapse_file now has to handle faults occurring during the collapse. This is done by re-validating the number of missing pages after acquiring the page cache lock for the final time. This fix is targeted at khugepaged, but the change also applies to MADV_COLLAPSE. MADV_COLLAPSE on a range with a userfaultfd will now return EBUSY if there are any missing pages (instead of succeeding on shmem and returning EINVAL on anonymous memory). There is also now a window during MADV_COLLAPSE where a fault on a missing page will cause the syscall to fail with EAGAIN. The fact that intermediate page cache state can no longer be observed before the rollback of a failed collapse is also technically a userspace-visible change (via at least SEEK_DATA and SEEK_END), but it is exceedingly unlikely that anything relies on being able to observe that transient state. Link: https://lkml.kernel.org/r/20230404120117.2562166-4-stevensd@google.comSigned-off-by:
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David Stevens authored
Add a rollback label to deal with failure, instead of continuously checking for RESULT_SUCCESS, to make it easier to add more failure cases. The refactoring also allows the collapse_file tracepoint to include hpage on success (instead of NULL). Link: https://lkml.kernel.org/r/20230404120117.2562166-3-stevensd@google.comSigned-off-by:
Yang Shi <shy828301@gmail.com> Acked-by:
Hugh Dickins <hughd@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jiaqi Yan <jiaqiyan@google.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by:
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