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mm/memfd: reserve hugetlb folios before allocation

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When we try to allocate a folio via alloc_hugetlb_folio_reserve(), we need
to ensure that there is an active reservation associated with the
allocation.  Otherwise, our allocation request would fail if there are no
active reservations made at that moment against any other allocations. 
This is because alloc_hugetlb_folio_reserve() checks h->resv_huge_pages
before proceeding with the allocation.

Therefore, to address this issue, we just need to make a reservation (by
calling hugetlb_reserve_pages()) before we try to allocate the folio. 
This will also ensure that proper region/subpool accounting is done
associated with our allocation.

Link: https://lkml.kernel.org/r/20250618053415.1036185-3-vivek.kasireddy@intel.com
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: Steve Sistare <steven.sistare@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Vivek Kasireddy
2025-06-17 22:30:54 -07:00
committed by Andrew Morton
parent 986f5f2b4b
commit 717cf93573
3 changed files with 19 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/hugetlb.h
View File

@@ -740,6 +740,11 @@ extern unsigned int default_hstate_idx;
#define default_hstate (hstates[default_hstate_idx])
static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
{
return HUGETLBFS_SB(inode->i_sb)->spool;
}
static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio)
{
return folio->_hugetlb_subpool;

5
mm/hugetlb.c
View File

@@ -284,11 +284,6 @@ static long hugepage_subpool_put_pages(struct hugepage_subpool *spool,
return ret;
}
static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
{
return HUGETLBFS_SB(inode->i_sb)->spool;
}
static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
{
return subpool_inode(file_inode(vma->vm_file));

17
mm/memfd.c
View File

@@ -70,7 +70,6 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
#ifdef CONFIG_HUGETLB_PAGE
struct folio *folio;
gfp_t gfp_mask;
int err;
if (is_file_hugepages(memfd)) {
/*
@@ -79,12 +78,19 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
* alloc from. Also, the folio will be pinned for an indefinite
* amount of time, so it is not expected to be migrated away.
*/
struct inode *inode = file_inode(memfd);
struct hstate *h = hstate_file(memfd);
int err = -ENOMEM;
long nr_resv;
gfp_mask = htlb_alloc_mask(h);
gfp_mask &= ~(__GFP_HIGHMEM | __GFP_MOVABLE);
idx >>= huge_page_order(h);
nr_resv = hugetlb_reserve_pages(inode, idx, idx + 1, NULL, 0);
if (nr_resv < 0)
return ERR_PTR(nr_resv);
folio = alloc_hugetlb_folio_reserve(h,
numa_node_id(),
NULL,
@@ -95,12 +101,17 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
idx);
if (err) {
folio_put(folio);
return ERR_PTR(err);
goto err_unresv;
}
hugetlb_set_folio_subpool(folio, subpool_inode(inode));
folio_unlock(folio);
return folio;
}
return ERR_PTR(-ENOMEM);
err_unresv:
if (nr_resv > 0)
hugetlb_unreserve_pages(inode, idx, idx + 1, 0);
return ERR_PTR(err);
}
#endif
return shmem_read_folio(memfd->f_mapping, idx);