[PATCH v3 5/6] mm: shmem: add mTHP size alignment in shmem_get_unmapped_area

Baolin Wang
2024-05-30T02:04:48Z

Although the top-level hugepage allocation can be turned off, anonymous shmem
can still use mTHP by configuring the sysfs interface located at
'/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/shmem_enabled'. Therefore,
add alignment for mTHP size to provide a suitable alignment address in
shmem_get_unmapped_area().

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Lance Yang <ioworker0@gmail.com>
---
mm/shmem.c | 36 +++++++++++++++++++++++++++---------
1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 493873d7246c..efc093ee7d4d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2394,6 +2394,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
unsigned long inflated_len;
unsigned long inflated_addr;
unsigned long inflated_offset;
+ unsigned long hpage_size;

if (len > TASK_SIZE)
return -ENOMEM;
@@ -2412,8 +2413,6 @@ unsigned long shmem_get_unmapped_area(struct file *file,

if (shmem_huge == SHMEM_HUGE_DENY)
return addr;
- if (len < HPAGE_PMD_SIZE)
- return addr;
if (flags & MAP_FIXED)
return addr;
/*
@@ -2425,8 +2424,11 @@ unsigned long shmem_get_unmapped_area(struct file *file,
if (uaddr == addr)
return addr;

+ hpage_size = HPAGE_PMD_SIZE;
if (shmem_huge != SHMEM_HUGE_FORCE) {
struct super_block *sb;
+ unsigned long __maybe_unused hpage_orders;
+ int order = 0;

if (file) {
VM_BUG_ON(file->f_op != &shmem_file_operations);
@@ -2439,18 +2441,34 @@ unsigned long shmem_get_unmapped_area(struct file *file,
if (IS_ERR(shm_mnt))
return addr;
sb = shm_mnt->mnt_sb;
+
+ /*
+ * Find the highest mTHP order used for anonymous shmem to
+ * provide a suitable alignment address.
+ */
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ hpage_orders = READ_ONCE(huge_anon_shmem_orders_always);
+ hpage_orders |= READ_ONCE(huge_anon_shmem_orders_within_size);
+ hpage_orders |= READ_ONCE(huge_anon_shmem_orders_madvise);
+ hpage_orders |= READ_ONCE(huge_anon_shmem_orders_inherit);
+ order = highest_order(hpage_orders);
+ hpage_size = PAGE_SIZE << order;
+#endif
}
- if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
+ if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER && !order)
return addr;
}

- offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
- if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
+ if (len < hpage_size)
+ return addr;
+
+ offset = (pgoff << PAGE_SHIFT) & (hpage_size - 1);
+ if (offset && offset + len < 2 * hpage_size)
return addr;
- if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
+ if ((addr & (hpage_size - 1)) == offset)
return addr;

- inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
+ inflated_len = len + hpage_size - PAGE_SIZE;
if (inflated_len > TASK_SIZE)
return addr;
if (inflated_len < len)
@@ -2463,10 +2481,10 @@ unsigned long shmem_get_unmapped_area(struct file *file,
if (inflated_addr & ~PAGE_MASK)
return addr;

- inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
+ inflated_offset = inflated_addr & (hpage_size - 1);
inflated_addr += offset - inflated_offset;
if (inflated_offset > offset)
- inflated_addr += HPAGE_PMD_SIZE;
+ inflated_addr += hpage_size;

if (inflated_addr > TASK_SIZE - len)
return addr;
--
2.39.3