kernel/linux.git/mm/gup.c, branch v6.12.91

mm: replace READ_ONCE() with standard page table accessors

2026-04-11T12:24:52+00:00

[ Upstream commit c0efdb373c3aaacb32db59cadb0710cac13e44ae ] Replace all READ_ONCE() with a standard page table accessors i.e pxdp_get() that defaults into READ_ONCE() in cases where platform does not override. Link: https://lkml.kernel.org/r/20251007063100.2396936-1-anshuman.khandual@arm.com Signed-off-by: Anshuman Khandual Acked-by: David Hildenbrand Reviewed-by: Lance Yang Reviewed-by: Wei Yang Reviewed-by: Dev Jain Signed-off-by: Andrew Morton Stable-dep-of: ffef67b93aa3 ("mm/memory: fix PMD/PUD checks in follow_pfnmap_start()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mm: folio_may_be_lru_cached() unless folio_test_large()

2025-10-02T11:44:11+00:00

[ Upstream commit 2da6de30e60dd9bb14600eff1cc99df2fa2ddae3 ] mm/swap.c and mm/mlock.c agree to drain any per-CPU batch as soon as a large folio is added: so collect_longterm_unpinnable_folios() just wastes effort when calling lru_add_drain[_all]() on a large folio. But although there is good reason not to batch up PMD-sized folios, we might well benefit from batching a small number of low-order mTHPs (though unclear how that "small number" limitation will be implemented). So ask if folio_may_be_lru_cached() rather than !folio_test_large(), to insulate those particular checks from future change. Name preferred to "folio_is_batchable" because large folios can well be put on a batch: it's just the per-CPU LRU caches, drained much later, which need care. Marked for stable, to counter the increase in lru_add_drain_all()s from "mm/gup: check ref_count instead of lru before migration". Link: https://lkml.kernel.org/r/57d2eaf8-3607-f318-e0c5-be02dce61ad0@google.com Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region") Signed-off-by: Hugh Dickins Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Cc: "Aneesh Kumar K.V" Cc: Axel Rasmussen Cc: Chris Li Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Johannes Weiner Cc: John Hubbard Cc: Keir Fraser Cc: Konstantin Khlebnikov Cc: Li Zhe Cc: Matthew Wilcox (Oracle) Cc: Peter Xu Cc: Rik van Riel Cc: Shivank Garg Cc: Vlastimil Babka Cc: Wei Xu Cc: Will Deacon Cc: yangge Cc: Yuanchu Xie Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton [ Clean cherry-pick now into this tree ] Signed-off-by: Hugh Dickins Signed-off-by: Sasha Levin

mm/gup: local lru_add_drain() to avoid lru_add_drain_all()

2025-10-02T11:44:11+00:00

[ Upstream commit a09a8a1fbb374e0053b97306da9dbc05bd384685 ] In many cases, if collect_longterm_unpinnable_folios() does need to drain the LRU cache to release a reference, the cache in question is on this same CPU, and much more efficiently drained by a preliminary local lru_add_drain(), than the later cross-CPU lru_add_drain_all(). Marked for stable, to counter the increase in lru_add_drain_all()s from "mm/gup: check ref_count instead of lru before migration". Note for clean backports: can take 6.16 commit a03db236aebf ("gup: optimize longterm pin_user_pages() for large folio") first. Link: https://lkml.kernel.org/r/66f2751f-283e-816d-9530-765db7edc465@google.com Signed-off-by: Hugh Dickins Acked-by: David Hildenbrand Cc: "Aneesh Kumar K.V" Cc: Axel Rasmussen Cc: Chris Li Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Johannes Weiner Cc: John Hubbard Cc: Keir Fraser Cc: Konstantin Khlebnikov Cc: Li Zhe Cc: Matthew Wilcox (Oracle) Cc: Peter Xu Cc: Rik van Riel Cc: Shivank Garg Cc: Vlastimil Babka Cc: Wei Xu Cc: Will Deacon Cc: yangge Cc: Yuanchu Xie Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton [ Clean cherry-pick now into this tree ] Signed-off-by: Hugh Dickins Signed-off-by: Sasha Levin

mm/gup: check ref_count instead of lru before migration

2025-09-25T09:13:50+00:00

[ Upstream commit 98c6d259319ecf6e8d027abd3f14b81324b8c0ad ] Patch series "mm: better GUP pin lru_add_drain_all()", v2. Series of lru_add_drain_all()-related patches, arising from recent mm/gup migration report from Will Deacon. This patch (of 5): Will Deacon reports:- When taking a longterm GUP pin via pin_user_pages(), __gup_longterm_locked() tries to migrate target folios that should not be longterm pinned, for example because they reside in a CMA region or movable zone. This is done by first pinning all of the target folios anyway, collecting all of the longterm-unpinnable target folios into a list, dropping the pins that were just taken and finally handing the list off to migrate_pages() for the actual migration. It is critically important that no unexpected references are held on the folios being migrated, otherwise the migration will fail and pin_user_pages() will return -ENOMEM to its caller. Unfortunately, it is relatively easy to observe migration failures when running pKVM (which uses pin_user_pages() on crosvm's virtual address space to resolve stage-2 page faults from the guest) on a 6.15-based Pixel 6 device and this results in the VM terminating prematurely. In the failure case, 'crosvm' has called mlock(MLOCK_ONFAULT) on its mapping of guest memory prior to the pinning. Subsequently, when pin_user_pages() walks the page-table, the relevant 'pte' is not present and so the faulting logic allocates a new folio, mlocks it with mlock_folio() and maps it in the page-table. Since commit 2fbb0c10d1e8 ("mm/munlock: mlock_page() munlock_page() batch by pagevec"), mlock/munlock operations on a folio (formerly page), are deferred. For example, mlock_folio() takes an additional reference on the target folio before placing it into a per-cpu 'folio_batch' for later processing by mlock_folio_batch(), which drops the refcount once the operation is complete. Processing of the batches is coupled with the LRU batch logic and can be forcefully drained with lru_add_drain_all() but as long as a folio remains unprocessed on the batch, its refcount will be elevated. This deferred batching therefore interacts poorly with the pKVM pinning scenario as we can find ourselves in a situation where the migration code fails to migrate a folio due to the elevated refcount from the pending mlock operation. Hugh Dickins adds:- !folio_test_lru() has never been a very reliable way to tell if an lru_add_drain_all() is worth calling, to remove LRU cache references to make the folio migratable: the LRU flag may be set even while the folio is held with an extra reference in a per-CPU LRU cache. 5.18 commit 2fbb0c10d1e8 may have made it more unreliable. Then 6.11 commit 33dfe9204f29 ("mm/gup: clear the LRU flag of a page before adding to LRU batch") tried to make it reliable, by moving LRU flag clearing; but missed the mlock/munlock batches, so still unreliable as reported. And it turns out to be difficult to extend 33dfe9204f29's LRU flag clearing to the mlock/munlock batches: if they do benefit from batching, mlock/munlock cannot be so effective when easily suppressed while !LRU. Instead, switch to an expected ref_count check, which was more reliable all along: some more false positives (unhelpful drains) than before, and never a guarantee that the folio will prove migratable, but better. Note on PG_private_2: ceph and nfs are still using the deprecated PG_private_2 flag, with the aid of netfs and filemap support functions. Although it is consistently matched by an increment of folio ref_count, folio_expected_ref_count() intentionally does not recognize it, and ceph folio migration currently depends on that for PG_private_2 folios to be rejected. New references to the deprecated flag are discouraged, so do not add it into the collect_longterm_unpinnable_folios() calculation: but longterm pinning of transiently PG_private_2 ceph and nfs folios (an uncommon case) may invoke a redundant lru_add_drain_all(). And this makes easy the backport to earlier releases: up to and including 6.12, btrfs also used PG_private_2, but without a ref_count increment. Note for stable backports: requires 6.16 commit 86ebd50224c0 ("mm: add folio_expected_ref_count() for reference count calculation"). Link: https://lkml.kernel.org/r/41395944-b0e3-c3ac-d648-8ddd70451d28@google.com Link: https://lkml.kernel.org/r/bd1f314a-fca1-8f19-cac0-b936c9614557@google.com Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region") Signed-off-by: Hugh Dickins Reported-by: Will Deacon Closes: https://lore.kernel.org/linux-mm/20250815101858.24352-1-will@kernel.org/ Acked-by: Kiryl Shutsemau Acked-by: David Hildenbrand Cc: "Aneesh Kumar K.V" Cc: Axel Rasmussen Cc: Chris Li Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Johannes Weiner Cc: John Hubbard Cc: Keir Fraser Cc: Konstantin Khlebnikov Cc: Li Zhe Cc: Matthew Wilcox (Oracle) Cc: Peter Xu Cc: Rik van Riel Cc: Shivank Garg Cc: Vlastimil Babka Cc: Wei Xu Cc: yangge Cc: Yuanchu Xie Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

gup: optimize longterm pin_user_pages() for large folio

2025-09-25T09:13:45+00:00

commit a03db236aebfaeadf79396dbd570896b870bda01 upstream. In the current implementation of longterm pin_user_pages(), we invoke collect_longterm_unpinnable_folios(). This function iterates through the list to check whether each folio belongs to the "longterm_unpinnabled" category. The folios in this list essentially correspond to a contiguous region of userspace addresses, with each folio representing a physical address in increments of PAGESIZE. If this userspace address range is mapped with large folio, we can optimize the performance of function collect_longterm_unpinnable_folios() by reducing the using of READ_ONCE() invoked in pofs_get_folio()->page_folio()->_compound_head(). Also, we can simplify the logic of collect_longterm_unpinnable_folios(). Instead of comparing with prev_folio after calling pofs_get_folio(), we can check whether the next page is within the same folio. The performance test results, based on v6.15, obtained through the gup_test tool from the kernel source tree are as follows. We achieve an improvement of over 66% for large folio with pagesize=2M. For small folio, we have only observed a very slight degradation in performance. Without this patch: [root@localhost ~] ./gup_test -HL -m 8192 -n 512 TAP version 13 1..1 # PIN_LONGTERM_BENCHMARK: Time: get:14391 put:10858 us# ok 1 ioctl status 0 # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 [root@localhost ~]# ./gup_test -LT -m 8192 -n 512 TAP version 13 1..1 # PIN_LONGTERM_BENCHMARK: Time: get:130538 put:31676 us# ok 1 ioctl status 0 # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 With this patch: [root@localhost ~] ./gup_test -HL -m 8192 -n 512 TAP version 13 1..1 # PIN_LONGTERM_BENCHMARK: Time: get:4867 put:10516 us# ok 1 ioctl status 0 # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 [root@localhost ~]# ./gup_test -LT -m 8192 -n 512 TAP version 13 1..1 # PIN_LONGTERM_BENCHMARK: Time: get:131798 put:31328 us# ok 1 ioctl status 0 # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 [lizhe.67@bytedance.com: whitespace fix, per David] Link: https://lkml.kernel.org/r/20250606091917.91384-1-lizhe.67@bytedance.com Link: https://lkml.kernel.org/r/20250606023742.58344-1-lizhe.67@bytedance.com Signed-off-by: Li Zhe Cc: David Hildenbrand Cc: Dev Jain Cc: Jason Gunthorpe Cc: John Hubbard Cc: Muchun Song Cc: Peter Xu Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/gup: revert "mm: gup: fix infinite loop within __get_longterm_locked"

2025-07-06T09:01:43+00:00

commit 517f496e1e61bd169d585dab4dd77e7147506322 upstream. After commit 1aaf8c122918 ("mm: gup: fix infinite loop within __get_longterm_locked") we are able to longterm pin folios that are not supposed to get longterm pinned, simply because they temporarily have the LRU flag cleared (esp. temporarily isolated). For example, two __get_longterm_locked() callers can race, or __get_longterm_locked() can race with anything else that temporarily isolates folios. The introducing commit mentions the use case of a driver that uses vm_ops->fault to insert pages allocated through cma_alloc() into the page tables, assuming they can later get longterm pinned. These pages/ folios would never have the LRU flag set and consequently cannot get isolated. There is no known in-tree user making use of that so far, fortunately. To handle that in the future -- and avoid retrying forever to isolate/migrate them -- we will need a different mechanism for the CMA area *owner* to indicate that it actually already allocated the page and is fine with longterm pinning it. The LRU flag is not suitable for that. Probably we can lookup the relevant CMA area and query the bitmap; we only have have to care about some races, probably. If already allocated, we could just allow longterm pinning) Anyhow, let's fix the "must not be longterm pinned" problem first by reverting the original commit. Link: https://lkml.kernel.org/r/20250611131314.594529-1-david@redhat.com Fixes: 1aaf8c122918 ("mm: gup: fix infinite loop within __get_longterm_locked") Signed-off-by: David Hildenbrand Closes: https://lore.kernel.org/all/20250522092755.GA3277597@tiffany/ Reported-by: Hyesoo Yu Reviewed-by: John Hubbard Cc: Jason Gunthorpe Cc: Peter Xu Cc: Zhaoyang Huang Cc: Aijun Sun Cc: Alistair Popple Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/gup: fix wrongly calculated returned value in fault_in_safe_writeable()

2025-04-25T08:47:53+00:00

commit 8c03ebd7cdc06bd0d2fecb4d1a609ef1dbb7d0aa upstream. Not like fault_in_readable() or fault_in_writeable(), in fault_in_safe_writeable() local variable 'start' is increased page by page to loop till the whole address range is handled. However, it mistakenly calculates the size of the handled range with 'uaddr - start'. Fix it here. Andreas said: : In gfs2, fault_in_iov_iter_writeable() is used in : gfs2_file_direct_read() and gfs2_file_read_iter(), so this potentially : affects buffered as well as direct reads. This bug could cause those : gfs2 functions to spin in a loop. Link: https://lkml.kernel.org/r/20250410035717.473207-1-bhe@redhat.com Link: https://lkml.kernel.org/r/20250410035717.473207-2-bhe@redhat.com Signed-off-by: Baoquan He Fixes: fe673d3f5bf1 ("mm: gup: make fault_in_safe_writeable() use fixup_user_fault()") Reviewed-by: Oscar Salvador Acked-by: David Hildenbrand Cc: Andreas Gruenbacher Cc: Yanjun.Zhu Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/gup: reject FOLL_SPLIT_PMD with hugetlb VMAs

2025-04-10T12:39:39+00:00

commit 8977752c8056a6a094a279004a49722da15bace3 upstream. Patch series "mm: fixes for device-exclusive entries (hmm)", v2. Discussing the PageTail() call in make_device_exclusive_range() with Willy, I recently discovered [1] that device-exclusive handling does not properly work with THP, making the hmm-tests selftests fail if THPs are enabled on the system. Looking into more details, I found that hugetlb is not properly fenced, and I realized that something that was bugging me for longer -- how device-exclusive entries interact with mapcounts -- completely breaks migration/swapout/split/hwpoison handling of these folios while they have device-exclusive PTEs. The program below can be used to allocate 1 GiB worth of pages and making them device-exclusive on a kernel with CONFIG_TEST_HMM. Once they are device-exclusive, these folios cannot get swapped out (proc$pid/smaps_rollup will always indicate 1 GiB RSS no matter how much one forces memory reclaim), and when having a memory block onlined to ZONE_MOVABLE, trying to offline it will loop forever and complain about failed migration of a page that should be movable. # echo offline > /sys/devices/system/memory/memory136/state # echo online_movable > /sys/devices/system/memory/memory136/state # ./hmm-swap & ... wait until everything is device-exclusive # echo offline > /sys/devices/system/memory/memory136/state [ 285.193431][T14882] page: refcount:2 mapcount:0 mapping:0000000000000000 index:0x7f20671f7 pfn:0x442b6a [ 285.196618][T14882] memcg:ffff888179298000 [ 285.198085][T14882] anon flags: 0x5fff0000002091c(referenced|uptodate| dirty|active|owner_2|swapbacked|node=1|zone=3|lastcpupid=0x7ff) [ 285.201734][T14882] raw: ... [ 285.204464][T14882] raw: ... [ 285.207196][T14882] page dumped because: migration failure [ 285.209072][T14882] page_owner tracks the page as allocated [ 285.210915][T14882] page last allocated via order 0, migratetype Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), id 14926, tgid 14926 (hmm-swap), ts 254506295376, free_ts 227402023774 [ 285.216765][T14882] post_alloc_hook+0x197/0x1b0 [ 285.218874][T14882] get_page_from_freelist+0x76e/0x3280 [ 285.220864][T14882] __alloc_frozen_pages_noprof+0x38e/0x2740 [ 285.223302][T14882] alloc_pages_mpol+0x1fc/0x540 [ 285.225130][T14882] folio_alloc_mpol_noprof+0x36/0x340 [ 285.227222][T14882] vma_alloc_folio_noprof+0xee/0x1a0 [ 285.229074][T14882] __handle_mm_fault+0x2b38/0x56a0 [ 285.230822][T14882] handle_mm_fault+0x368/0x9f0 ... This series fixes all issues I found so far. There is no easy way to fix without a bigger rework/cleanup. I have a bunch of cleanups on top (some previous sent, some the result of the discussion in v1) that I will send out separately once this landed and I get to it. I wish we could just use some special present PROT_NONE PTEs instead of these (non-present, non-none) fake-swap entries; but that just results in the same problem we keep having (lack of spare PTE bits), and staring at other similar fake-swap entries, that ship has sailed. With this series, make_device_exclusive() doesn't actually belong into mm/rmap.c anymore, but I'll leave moving that for another day. I only tested this series with the hmm-tests selftests due to lack of HW, so I'd appreciate some testing, especially if the interaction between two GPUs wanting a device-exclusive entry works as expected. #include #include #include #include #include #include #include #include #include #include #define HMM_DMIRROR_EXCLUSIVE _IOWR('H', 0x05, struct hmm_dmirror_cmd) struct hmm_dmirror_cmd { __u64 addr; __u64 ptr; __u64 npages; __u64 cpages; __u64 faults; }; const size_t size = 1 * 1024 * 1024 * 1024ul; const size_t chunk_size = 2 * 1024 * 1024ul; int main(void) { struct hmm_dmirror_cmd cmd; size_t cur_size; int fd, ret; char *addr, *mirror; fd = open("/dev/hmm_dmirror1", O_RDWR, 0); if (fd < 0) { perror("open failed\n"); exit(1); } addr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (addr == MAP_FAILED) { perror("mmap failed\n"); exit(1); } madvise(addr, size, MADV_NOHUGEPAGE); memset(addr, 1, size); mirror = malloc(chunk_size); for (cur_size = 0; cur_size < size; cur_size += chunk_size) { cmd.addr = (uintptr_t)addr + cur_size; cmd.ptr = (uintptr_t)mirror; cmd.npages = chunk_size / getpagesize(); ret = ioctl(fd, HMM_DMIRROR_EXCLUSIVE, &cmd); if (ret) { perror("ioctl failed\n"); exit(1); } } pause(); return 0; } [1] https://lkml.kernel.org/r/25e02685-4f1d-47fa-be5b-01ff85bb0ce2@redhat.com This patch (of 17): We only have two FOLL_SPLIT_PMD users. While uprobe refuses hugetlb early, make_device_exclusive_range() can end up getting called on hugetlb VMAs. Right now, this means that with a PMD-sized hugetlb page, we can end up calling split_huge_pmd(), because pmd_trans_huge() also succeeds with hugetlb PMDs. For example, using a modified hmm-test selftest one can trigger: [ 207.017134][T14945] ------------[ cut here ]------------ [ 207.018614][T14945] kernel BUG at mm/page_table_check.c:87! [ 207.019716][T14945] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI [ 207.021072][T14945] CPU: 3 UID: 0 PID: ... [ 207.023036][T14945] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014 [ 207.024834][T14945] RIP: 0010:page_table_check_clear.part.0+0x488/0x510 [ 207.026128][T14945] Code: ... [ 207.029965][T14945] RSP: 0018:ffffc9000cb8f348 EFLAGS: 00010293 [ 207.031139][T14945] RAX: 0000000000000000 RBX: 00000000ffffffff RCX: ffffffff8249a0cd [ 207.032649][T14945] RDX: ffff88811e883c80 RSI: ffffffff8249a357 RDI: ffff88811e883c80 [ 207.034183][T14945] RBP: ffff888105c0a050 R08: 0000000000000005 R09: 0000000000000000 [ 207.035688][T14945] R10: 00000000ffffffff R11: 0000000000000003 R12: 0000000000000001 [ 207.037203][T14945] R13: 0000000000000200 R14: 0000000000000001 R15: dffffc0000000000 [ 207.038711][T14945] FS: 00007f2783275740(0000) GS:ffff8881f4980000(0000) knlGS:0000000000000000 [ 207.040407][T14945] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 207.041660][T14945] CR2: 00007f2782c00000 CR3: 0000000132356000 CR4: 0000000000750ef0 [ 207.043196][T14945] PKRU: 55555554 [ 207.043880][T14945] Call Trace: [ 207.044506][T14945] [ 207.045086][T14945] ? __die+0x51/0x92 [ 207.045864][T14945] ? die+0x29/0x50 [ 207.046596][T14945] ? do_trap+0x250/0x320 [ 207.047430][T14945] ? do_error_trap+0xe7/0x220 [ 207.048346][T14945] ? page_table_check_clear.part.0+0x488/0x510 [ 207.049535][T14945] ? handle_invalid_op+0x34/0x40 [ 207.050494][T14945] ? page_table_check_clear.part.0+0x488/0x510 [ 207.051681][T14945] ? exc_invalid_op+0x2e/0x50 [ 207.052589][T14945] ? asm_exc_invalid_op+0x1a/0x20 [ 207.053596][T14945] ? page_table_check_clear.part.0+0x1fd/0x510 [ 207.054790][T14945] ? page_table_check_clear.part.0+0x487/0x510 [ 207.055993][T14945] ? page_table_check_clear.part.0+0x488/0x510 [ 207.057195][T14945] ? page_table_check_clear.part.0+0x487/0x510 [ 207.058384][T14945] __page_table_check_pmd_clear+0x34b/0x5a0 [ 207.059524][T14945] ? __pfx___page_table_check_pmd_clear+0x10/0x10 [ 207.060775][T14945] ? __pfx___mutex_unlock_slowpath+0x10/0x10 [ 207.061940][T14945] ? __pfx___lock_acquire+0x10/0x10 [ 207.062967][T14945] pmdp_huge_clear_flush+0x279/0x360 [ 207.064024][T14945] split_huge_pmd_locked+0x82b/0x3750 ... Before commit 9cb28da54643 ("mm/gup: handle hugetlb in the generic follow_page_mask code"), we would have ignored the flag; instead, let's simply refuse the combination completely in check_vma_flags(): the caller is likely not prepared to handle any hugetlb folios. We'll teach make_device_exclusive_range() separately to ignore any hugetlb folios as a future-proof safety net. Link: https://lkml.kernel.org/r/20250210193801.781278-1-david@redhat.com Link: https://lkml.kernel.org/r/20250210193801.781278-2-david@redhat.com Fixes: 9cb28da54643 ("mm/gup: handle hugetlb in the generic follow_page_mask code") Signed-off-by: David Hildenbrand Reviewed-by: John Hubbard Reviewed-by: Alistair Popple Tested-by: Alistair Popple Cc: Alex Shi Cc: Danilo Krummrich Cc: Dave Airlie Cc: Jann Horn Cc: Jason Gunthorpe Cc: Jerome Glisse Cc: Jonathan Corbet Cc: Karol Herbst Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Lyude Cc: "Masami Hiramatsu (Google)" Cc: Oleg Nesterov Cc: Pasha Tatashin Cc: Peter Xu Cc: Peter Zijlstra (Intel) Cc: SeongJae Park Cc: Vlastimil Babka Cc: Yanteng Si Cc: Simona Vetter Cc: Barry Song Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: gup: fix infinite loop within __get_longterm_locked

2025-02-17T09:05:36+00:00

commit 1aaf8c122918aa8897605a9aa1e8ed6600d6f930 upstream. We can run into an infinite loop in __get_longterm_locked() when collect_longterm_unpinnable_folios() finds only folios that are isolated from the LRU or were never added to the LRU. This can happen when all folios to be pinned are never added to the LRU, for example when vm_ops->fault allocated pages using cma_alloc() and never added them to the LRU. Fix it by simply taking a look at the list in the single caller, to see if anything was added. [zhaoyang.huang@unisoc.com: move definition of local] Link: https://lkml.kernel.org/r/20250122012604.3654667-1-zhaoyang.huang@unisoc.com Link: https://lkml.kernel.org/r/20250121020159.3636477-1-zhaoyang.huang@unisoc.com Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()") Signed-off-by: Zhaoyang Huang Reviewed-by: John Hubbard Reviewed-by: David Hildenbrand Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Cc: Aijun Sun Cc: Alistair Popple Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/gup: handle NULL pages in unpin_user_pages()

2024-12-14T19:03:32+00:00

commit a1268be280d8e484ab3606d7476edd0f14bb9961 upstream. The recent addition of "pofs" (pages or folios) handling to gup has a flaw: it assumes that unpin_user_pages() handles NULL pages in the pages** array. That's not the case, as I discovered when I ran on a new configuration on my test machine. Fix this by skipping NULL pages in unpin_user_pages(), just like unpin_folios() already does. Details: when booting on x86 with "numa=fake=2 movablecore=4G" on Linux 6.12, and running this: tools/testing/selftests/mm/gup_longterm ...I get the following crash: BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:sanity_check_pinned_pages+0x3a/0x2d0 ... Call Trace: ? __die_body+0x66/0xb0 ? page_fault_oops+0x30c/0x3b0 ? do_user_addr_fault+0x6c3/0x720 ? irqentry_enter+0x34/0x60 ? exc_page_fault+0x68/0x100 ? asm_exc_page_fault+0x22/0x30 ? sanity_check_pinned_pages+0x3a/0x2d0 unpin_user_pages+0x24/0xe0 check_and_migrate_movable_pages_or_folios+0x455/0x4b0 __gup_longterm_locked+0x3bf/0x820 ? mmap_read_lock_killable+0x12/0x50 ? __pfx_mmap_read_lock_killable+0x10/0x10 pin_user_pages+0x66/0xa0 gup_test_ioctl+0x358/0xb20 __se_sys_ioctl+0x6b/0xc0 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x76/0x7e Link: https://lkml.kernel.org/r/20241121034933.77502-1-jhubbard@nvidia.com Fixes: 94efde1d1539 ("mm/gup: avoid an unnecessary allocation call for FOLL_LONGTERM cases") Signed-off-by: John Hubbard Acked-by: David Hildenbrand Cc: Oscar Salvador Cc: Vivek Kasireddy Cc: Dave Airlie Cc: Gerd Hoffmann Cc: Matthew Wilcox Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Peter Xu Cc: Arnd Bergmann Cc: Daniel Vetter Cc: Dongwon Kim Cc: Hugh Dickins Cc: Junxiao Chang Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman