On 25.06.24 11:06, Gavin Shan wrote:
For shmem files, it's possible that PMD-sized page cache can't be
supported by xarray. For example, 512MB page cache on ARM64 when
the base page size is 64KB can't be supported by xarray. It leads
to errors as the following messages indicate when this sort of xarray
entry is split.
WARNING: CPU: 34 PID: 7578 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128
Modules linked in: binfmt_misc 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: 34 PID: 7578 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 : ffff8000882af5f0
x29: ffff8000882af5f0 x28: ffff8000882af650 x27: ffff8000882af768
x26: 0000000000000cc0 x25: 000000000000000d x24: ffff00010625b858
x23: ffff8000882af650 x22: ffffffdfc0900000 x21: 0000000000000000
x20: 0000000000000000 x19: ffffffdfc0900000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000018000000000 x15: 52f8004000000000
x14: 0000e00000000000 x13: 0000000000002000 x12: 0000000000000020
x11: 52f8000000000000 x10: 52f8e1c0ffff6000 x9 : ffffbeb9619a681c
x8 : 0000000000000003 x7 : 0000000000000000 x6 : ffff00010b02ddb0
x5 : ffffbeb96395e378 x4 : 0000000000000000 x3 : 0000000000000cc0
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
shmem_undo_range+0x2bc/0x6a8
shmem_fallocate+0x134/0x430
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 disabling PMD-sized page cache when HPAGE_PMD_ORDER is
larger than MAX_PAGECACHE_ORDER.
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
mm/shmem.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index a8b181a63402..5453875e3810 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -541,8 +541,9 @@ static bool shmem_confirm_swap(struct address_space *mapping,
static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER;
-bool shmem_is_huge(struct inode *inode, pgoff_t index, bool shmem_huge_force,
- struct mm_struct *mm, unsigned long vm_flags)
+static bool __shmem_is_huge(struct inode *inode, pgoff_t index,
+ bool shmem_huge_force, struct mm_struct *mm,
+ unsigned long vm_flags)
{
loff_t i_size;
@@ -573,6 +574,16 @@ bool shmem_is_huge(struct inode *inode, pgoff_t index, bool shmem_huge_force,
}
}
+bool shmem_is_huge(struct inode *inode, pgoff_t index,
+ bool shmem_huge_force, struct mm_struct *mm,
+ unsigned long vm_flags)
+{
+ if (!__shmem_is_huge(inode, index, shmem_huge_force, mm, vm_flags))
+ return false;
+
+ return HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER;
Why not check for that upfront?
+}
+
#if defined(CONFIG_SYSFS)
static int shmem_parse_huge(const char *str)
{
This should make __thp_vma_allowable_orders() happy for shmem, and consequently, also khugepaged IIRC.
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
@Ryan,
should we do something like the following on top? The use of PUD_ORDER for ordinary pagecache is
wrong. Really only DAX is special and can support that in its own weird ways.
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 2aa986a5cd1b..ac63233fed6c 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -72,14 +72,25 @@ extern struct kobj_attribute shmem_enabled_attr;
#define THP_ORDERS_ALL_ANON ((BIT(PMD_ORDER + 1) - 1) & ~(BIT(0) | BIT(1)))
/*
- * Mask of all large folio orders supported for file THP.
+ * Mask of all large folio orders supported for FSDAX THP.
*/
-#define THP_ORDERS_ALL_FILE (BIT(PMD_ORDER) | BIT(PUD_ORDER))
+#define THP_ORDERS_ALL_DAX (BIT(PMD_ORDER) | BIT(PUD_ORDER))
+
+
+/*
+ * Mask of all large folio orders supported for ordinary pagecache (file/shmem)
+ * THP.
+ */
+#if PMD_ORDER <= MAX_PAGECACHE_ORDER
+#define THP_ORDERS_ALL_FILE 0
+#else
+#define THP_ORDERS_ALL_FILE (BIT(PMD_ORDER))
+#endif
/*
* Mask of all large folio orders supported for THP.
*/
-#define THP_ORDERS_ALL (THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_FILE)
+#define THP_ORDERS_ALL (THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_FILE )
#define TVA_SMAPS (1 << 0) /* Will be used for procfs */
#define TVA_IN_PF (1 << 1) /* Page fault handler */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 89932fd0f62e..95d4a2edae39 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -88,9 +88,15 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
bool smaps = tva_flags & TVA_SMAPS;
bool in_pf = tva_flags & TVA_IN_PF;
bool enforce_sysfs = tva_flags & TVA_ENFORCE_SYSFS;
+
/* Check the intersection of requested and supported orders. */
- orders &= vma_is_anonymous(vma) ?
- THP_ORDERS_ALL_ANON : THP_ORDERS_ALL_FILE;
+ if (vma_is_anonymous(vma))
+ orders &= THP_ORDERS_ALL_ANON;
+ else if (vma_is_dax(vma))
+ orders &= THP_ORDERS_ALL_DAX;
+ else
+ orders &= THP_ORDERS_ALL_FILE;
+
if (!orders)
return 0;
--
Cheers,
David / dhildenb
