The patch titled
Subject: mm/filemap: skip to allocate PMD-sized folios if needed
has been added to the -mm mm-unstable branch. Its filename is
mm-filemap-skip-to-allocate-pmd-sized-folios-if-needed.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-filemap-skip-to-allocate-pmd-sized-folios-if-needed.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Gavin Shan <gshan@xxxxxxxxxx>
Subject: mm/filemap: skip to allocate PMD-sized folios if needed
Date: Tue, 25 Jun 2024 19:06:44 +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/20240625090646.1194644-3-gshan@xxxxxxxxxx
Fixes: 4687fdbb805a ("mm/filemap: Support VM_HUGEPAGE for file mappings")
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Zhenyu Zhang <zhenyzha@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxx> [5.18+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/filemap.c~mm-filemap-skip-to-allocate-pmd-sized-folios-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@xxxxxxxxxx are
mm-filemap-make-max_pagecache_order-acceptable-to-xarray.patch
mm-filemap-skip-to-allocate-pmd-sized-folios-if-needed.patch
mm-readahead-limit-page-cache-size-in-page_cache_ra_order.patch
mm-shmem-disable-pmd-sized-page-cache-if-needed.patch
