Commit 986f5f2b authored by Vivek Kasireddy's avatar Vivek Kasireddy Committed by Andrew Morton
Browse files

mm/hugetlb: make hugetlb_reserve_pages() return nr of entries updated 

Patch series "mm/memfd: Reserve hugetlb folios before allocation", v4.

There are cases when we try to pin a folio but discover that it has not
been faulted-in.  So, we try to allocate it in memfd_alloc_folio() but the
allocation request may not succeed if there are no active reservations in
the system at that instant.

Therefore, making a reservation (by calling hugetlb_reserve_pages())
associated with the allocation will ensure that our request would not fail
due to lack of reservations.  This will also ensure that proper
region/subpool accounting is done with our allocation.


This patch (of 3):

Currently, hugetlb_reserve_pages() returns a bool to indicate whether the
reservation map update for the range [from, to] was successful or not. 
This is not sufficient for the case where the caller needs to determine
how many entries were updated for the range.

Therefore, have hugetlb_reserve_pages() return the number of entries
updated in the reservation map associated with the range [from, to]. 
Also, update the callers of hugetlb_reserve_pages() to handle the new
return value.

Link: https://lkml.kernel.org/r/20250618053415.1036185-1-vivek.kasireddy@intel.com
Link: https://lkml.kernel.org/r/20250618053415.1036185-2-vivek.kasireddy@intel.com


Signed-off-by: default avatarVivek 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent d29d64af

fs/hugetlbfs/inode.c

+4 −4
Original line number Diff line number Diff line
@@ -150,10 +150,10 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) 
	if (inode->i_flags & S_PRIVATE)

		vm_flags |= VM_NORESERVE;



	if (!hugetlb_reserve_pages(inode,

	if (hugetlb_reserve_pages(inode,

				vma->vm_pgoff >> huge_page_order(h),

				len >> huge_page_shift(h), vma,

				vm_flags))

				vm_flags) < 0)

		goto out;



	ret = 0;
@@ -1561,9 +1561,9 @@ struct file *hugetlb_file_setup(const char *name, size_t size, 
	inode->i_size = size;

	clear_nlink(inode);



	if (!hugetlb_reserve_pages(inode, 0,

	if (hugetlb_reserve_pages(inode, 0,

			size >> huge_page_shift(hstate_inode(inode)), NULL,

			acctflag))

			acctflag) < 0)

		file = ERR_PTR(-ENOMEM);

	else

		file = alloc_file_pseudo(inode, mnt, name, O_RDWR,

include/linux/hugetlb.h

+1 −1
Original line number Diff line number Diff line
@@ -149,7 +149,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, 
			     uffd_flags_t flags,

			     struct folio **foliop);

#endif /* CONFIG_USERFAULTFD */

bool hugetlb_reserve_pages(struct inode *inode, long from, long to,

long hugetlb_reserve_pages(struct inode *inode, long from, long to,

						struct vm_area_struct *vma,

						vm_flags_t vm_flags);

long hugetlb_unreserve_pages(struct inode *inode, long start, long end,

mm/hugetlb.c

+13 −6
Original line number Diff line number Diff line
@@ -7244,8 +7244,15 @@ long hugetlb_change_protection(struct vm_area_struct *vma, 
	return pages > 0 ? (pages << h->order) : pages;

}



/* Return true if reservation was successful, false otherwise.  */

bool hugetlb_reserve_pages(struct inode *inode,

/*

 * Update the reservation map for the range [from, to].

 *

 * Returns the number of entries that would be added to the reservation map

 * associated with the range [from, to].  This number is greater or equal to

 * zero. -EINVAL or -ENOMEM is returned in case of any errors.

 */



long hugetlb_reserve_pages(struct inode *inode,

					long from, long to,

					struct vm_area_struct *vma,

					vm_flags_t vm_flags)
@@ -7260,7 +7267,7 @@ bool hugetlb_reserve_pages(struct inode *inode, 
	/* This should never happen */

	if (from > to) {

		VM_WARN(1, "%s called with a negative range\n", __func__);

		return false;

		return -EINVAL;

	}



	/*
@@ -7275,7 +7282,7 @@ bool hugetlb_reserve_pages(struct inode *inode, 
	 * without using reserves

	 */

	if (vm_flags & VM_NORESERVE)

		return true;

		return 0;



	/*

	 * Shared mappings base their reservation on the number of pages that
@@ -7382,7 +7389,7 @@ bool hugetlb_reserve_pages(struct inode *inode, 
			hugetlb_cgroup_put_rsvd_cgroup(h_cg);

		}

	}

	return true;

	return chg;



out_put_pages:

	spool_resv = chg - gbl_reserve;
@@ -7410,7 +7417,7 @@ bool hugetlb_reserve_pages(struct inode *inode, 
		kref_put(&resv_map->refs, resv_map_release);

		set_vma_resv_map(vma, NULL);

	}

	return false;

	return chg < 0 ? chg : add < 0 ? add : -EINVAL;

}



long hugetlb_unreserve_pages(struct inode *inode, long start, long end,