The patch titled Subject: mm/filemap: skip to create PMD-sized page cache if needed has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-filemap-skip-to-create-pmd-sized-page-cache-if-needed.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Gavin Shan gshan@redhat.com Subject: mm/filemap: skip to create PMD-sized page cache if needed Date: Thu, 27 Jun 2024 10:39:51 +1000
On ARM64, HPAGE_PMD_ORDER is 13 when the base page size is 64KB. The PMD-sized page cache can't be supported by xarray as the following error messages indicate.
------------[ cut here ]------------ WARNING: CPU: 35 PID: 7484 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128 Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib \ nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct \ nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 \ ip_set rfkill nf_tables nfnetlink vfat fat virtio_balloon drm \ fuse xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 \ sha1_ce virtio_net net_failover virtio_console virtio_blk failover \ dimlib virtio_mmio CPU: 35 PID: 7484 Comm: test Kdump: loaded Tainted: G W 6.10.0-rc5-gavin+ #9 Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20240524-1.el9 05/24/2024 pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : xas_split_alloc+0xf8/0x128 lr : split_huge_page_to_list_to_order+0x1c4/0x720 sp : ffff800087a4f6c0 x29: ffff800087a4f6c0 x28: ffff800087a4f720 x27: 000000001fffffff x26: 0000000000000c40 x25: 000000000000000d x24: ffff00010625b858 x23: ffff800087a4f720 x22: ffffffdfc0780000 x21: 0000000000000000 x20: 0000000000000000 x19: ffffffdfc0780000 x18: 000000001ff40000 x17: 00000000ffffffff x16: 0000018000000000 x15: 51ec004000000000 x14: 0000e00000000000 x13: 0000000000002000 x12: 0000000000000020 x11: 51ec000000000000 x10: 51ece1c0ffff8000 x9 : ffffbeb961a44d28 x8 : 0000000000000003 x7 : ffffffdfc0456420 x6 : ffff0000e1aa6eb8 x5 : 20bf08b4fe778fca x4 : ffffffdfc0456420 x3 : 0000000000000c40 x2 : 000000000000000d x1 : 000000000000000c x0 : 0000000000000000 Call trace: xas_split_alloc+0xf8/0x128 split_huge_page_to_list_to_order+0x1c4/0x720 truncate_inode_partial_folio+0xdc/0x160 truncate_inode_pages_range+0x1b4/0x4a8 truncate_pagecache_range+0x84/0xa0 xfs_flush_unmap_range+0x70/0x90 [xfs] xfs_file_fallocate+0xfc/0x4d8 [xfs] vfs_fallocate+0x124/0x2e8 ksys_fallocate+0x4c/0xa0 __arm64_sys_fallocate+0x24/0x38 invoke_syscall.constprop.0+0x7c/0xd8 do_el0_svc+0xb4/0xd0 el0_svc+0x44/0x1d8 el0t_64_sync_handler+0x134/0x150 el0t_64_sync+0x17c/0x180
Fix it by skipping to allocate PMD-sized page cache when its size is larger than MAX_PAGECACHE_ORDER. For this specific case, we will fall to regular path where the readahead window is determined by BDI's sysfs file (read_ahead_kb).
Link: https://lkml.kernel.org/r/20240627003953.1262512-4-gshan@redhat.com Fixes: 4687fdbb805a ("mm/filemap: Support VM_HUGEPAGE for file mappings") Signed-off-by: Gavin Shan gshan@redhat.com Suggested-by: David Hildenbrand david@redhat.com Acked-by: David Hildenbrand david@redhat.com Cc: Darrick J. Wong djwong@kernel.org Cc: Don Dutile ddutile@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Ryan Roberts ryan.roberts@arm.com Cc: William Kucharski william.kucharski@oracle.com Cc: Zhenyu Zhang zhenyzha@redhat.com Cc: stable@vger.kernel.org [5.18+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/filemap.c~mm-filemap-skip-to-create-pmd-sized-page-cache-if-needed +++ a/mm/filemap.c @@ -3124,7 +3124,7 @@ static struct file *do_sync_mmap_readahe
#ifdef CONFIG_TRANSPARENT_HUGEPAGE /* Use the readahead code, even if readahead is disabled */ - if (vm_flags & VM_HUGEPAGE) { + if ((vm_flags & VM_HUGEPAGE) && HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER) { fpin = maybe_unlock_mmap_for_io(vmf, fpin); ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1); ra->size = HPAGE_PMD_NR; _
Patches currently in -mm which might be from gshan@redhat.com are
mm-filemap-make-max_pagecache_order-acceptable-to-xarray.patch mm-readahead-limit-page-cache-size-in-page_cache_ra_order.patch mm-filemap-skip-to-create-pmd-sized-page-cache-if-needed.patch mm-shmem-disable-pmd-sized-page-cache-if-needed.patch