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

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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: 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 22:30:53 -07:00
committed by Andrew Morton
parent d29d64afa2
commit 986f5f2b4b
3 changed files with 18 additions and 11 deletions
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19
mm/hugetlb.c
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@@ -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 @@ out_err:
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,