[PATCH v4 1/3] mm/hugetlb: Make hugetlb_reserve_pages() return nr of entries updated

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

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.

Cc: Steve Sistare <steven.sistare@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 fs/hugetlbfs/inode.c    |  8 ++++----
 include/linux/hugetlb.h |  2 +-
 mm/hugetlb.c            | 19 +++++++++++++------
 3 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index e4de5425838d..00b2d1a032fd 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -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,
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 42f374e828a2..d8310b0f36dd 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -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,
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f74c54ecf955..6b34152744cc 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7267,8 +7267,15 @@ 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)
@@ -7283,7 +7290,7 @@ 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;
 	}
 
 	/*
@@ -7298,7 +7305,7 @@ 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
@@ -7405,7 +7412,7 @@ 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;
@@ -7433,7 +7440,7 @@ 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,
-- 
2.49.0