mm/filemap: remove hugetlb special casing in filemap.c

Remove special cased hugetlb handling code within the page cache by
changing the granularity of ->index to the base page size rather than the
huge page size.  The motivation of this patch is to reduce complexity
within the filemap code while also increasing performance by removing
branches that are evaluated on every page cache lookup.

To support the change in index, new wrappers for hugetlb page cache
interactions are added.  These wrappers perform the conversion to a linear
index which is now expected by the page cache for huge pages.

========================= PERFORMANCE ======================================

Perf was used to check the performance differences after the patch. 
Overall the performance is similar to mainline with a very small larger
overhead that occurs in __filemap_add_folio() and
hugetlb_add_to_page_cache().  This is because of the larger overhead that
occurs in xa_load() and xa_store() as the xarray is now using more entries
to store hugetlb folios in the page cache.

Timing

aarch64
    2MB Page Size
        6.5-rc3 + this patch:
            [root@sidhakum-ol9-1 hugepages]# time fallocate -l 700GB test.txt
            real    1m49.568s
            user    0m0.000s
            sys     1m49.461s

        6.5-rc3:
            [root]# time fallocate -l 700GB test.txt
            real    1m47.495s
            user    0m0.000s
            sys     1m47.370s
    1GB Page Size
        6.5-rc3 + this patch:
            [root@sidhakum-ol9-1 hugepages1G]# time fallocate -l 700GB test.txt
            real    1m47.024s
            user    0m0.000s
            sys     1m46.921s

        6.5-rc3:
            [root@sidhakum-ol9-1 hugepages1G]# time fallocate -l 700GB test.txt
            real    1m44.551s
            user    0m0.000s
            sys     1m44.438s

x86
    2MB Page Size
        6.5-rc3 + this patch:
            [root@sidhakum-ol9-2 hugepages]# time fallocate -l 100GB test.txt
            real    0m22.383s
            user    0m0.000s
            sys     0m22.255s

        6.5-rc3:
            [opc@sidhakum-ol9-2 hugepages]$ time sudo fallocate -l 100GB /dev/hugepages/test.txt
            real    0m22.735s
            user    0m0.038s
            sys     0m22.567s

    1GB Page Size
        6.5-rc3 + this patch:
            [root@sidhakum-ol9-2 hugepages1GB]# time fallocate -l 100GB test.txt
            real    0m25.786s
            user    0m0.001s
            sys     0m25.589s

        6.5-rc3:
            [root@sidhakum-ol9-2 hugepages1G]# time fallocate -l 100GB test.txt
            real    0m33.454s
            user    0m0.001s
            sys     0m33.193s

aarch64:
    workload - fallocate a 700GB file backed by huge pages

    6.5-rc3 + this patch:
        2MB Page Size:
            --100.00%--__arm64_sys_fallocate
                          ksys_fallocate
                          vfs_fallocate
                          hugetlbfs_fallocate
                          |
                          |--95.04%--__pi_clear_page
                          |
                          |--3.57%--clear_huge_page
                          |          |
                          |          |--2.63%--rcu_all_qs
                          |          |
                          |           --0.91%--__cond_resched
                          |
                           --0.67%--__cond_resched
            0.17%     0.00%             0  fallocate  [kernel.vmlinux]       [k] hugetlb_add_to_page_cache
            0.14%     0.10%            11  fallocate  [kernel.vmlinux]       [k] __filemap_add_folio

    6.5-rc3
        2MB Page Size:
                --100.00%--__arm64_sys_fallocate
                          ksys_fallocate
                          vfs_fallocate
                          hugetlbfs_fallocate
                          |
                          |--94.91%--__pi_clear_page
                          |
                          |--4.11%--clear_huge_page
                          |          |
                          |          |--3.00%--rcu_all_qs
                          |          |
                          |           --1.10%--__cond_resched
                          |
                           --0.59%--__cond_resched
            0.08%     0.01%             1  fallocate  [kernel.kallsyms]  [k] hugetlb_add_to_page_cache
            0.05%     0.03%             3  fallocate  [kernel.kallsyms]  [k] __filemap_add_folio

x86
    workload - fallocate a 100GB file backed by huge pages

    6.5-rc3 + this patch:
        2MB Page Size:
            hugetlbfs_fallocate
            |
            --99.57%--clear_huge_page
                |
                --98.47%--clear_page_erms
                    |
                    --0.53%--asm_sysvec_apic_timer_interrupt

            0.04%     0.04%             1  fallocate  [kernel.kallsyms]     [k] xa_load
            0.04%     0.00%             0  fallocate  [kernel.kallsyms]     [k] hugetlb_add_to_page_cache
            0.04%     0.00%             0  fallocate  [kernel.kallsyms]     [k] __filemap_add_folio
            0.04%     0.00%             0  fallocate  [kernel.kallsyms]     [k] xas_store

    6.5-rc3
        2MB Page Size:
                --99.93%--__x64_sys_fallocate
                          vfs_fallocate
                          hugetlbfs_fallocate
                          |
                           --99.38%--clear_huge_page
                                     |
                                     |--98.40%--clear_page_erms
                                     |
                                      --0.59%--__cond_resched
            0.03%     0.03%             1  fallocate  [kernel.kallsyms]  [k] __filemap_add_folio

========================= TESTING ======================================

This patch passes libhugetlbfs tests and LTP hugetlb tests

********** TEST SUMMARY
*                      2M
*                      32-bit 64-bit
*     Total testcases:   110    113
*             Skipped:     0      0
*                PASS:   107    113
*                FAIL:     0      0
*    Killed by signal:     3      0
*   Bad configuration:     0      0
*       Expected FAIL:     0      0
*     Unexpected PASS:     0      0
*    Test not present:     0      0
* Strange test result:     0      0
**********

    Done executing testcases.
    LTP Version:  20220527-178-g2761a81c4

page migration was also tested using Mike Kravetz's test program.[8]

[dan.carpenter@linaro.org: fix an NULL vs IS_ERR() bug]
  Link: https://lkml.kernel.org/r/1772c296-1417-486f-8eef-171af2192681@moroto.mountain
Link: https://lkml.kernel.org/r/20230926192017.98183-1-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reported-and-tested-by: syzbot+c225dea486da4d5592bd@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c225dea486da4d5592bd
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

3 files changed, 19 insertions, 53 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 9481ffaf24e6..340c693112a9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -131,11 +131,8 @@ static void page_cache_delete(struct address_space *mapping,
 
 	mapping_set_update(&xas, mapping);
 
-	/* hugetlb pages are represented by a single entry in the xarray */
-	if (!folio_test_hugetlb(folio)) {
-		xas_set_order(&xas, folio->index, folio_order(folio));
-		nr = folio_nr_pages(folio);
-	}
+	xas_set_order(&xas, folio->index, folio_order(folio));
+	nr = folio_nr_pages(folio);
 
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 
@@ -234,7 +231,7 @@ void filemap_free_folio(struct address_space *mapping, struct folio *folio)
 	if (free_folio)
 		free_folio(folio);
 
-	if (folio_test_large(folio) && !folio_test_hugetlb(folio))
+	if (folio_test_large(folio))
 		refs = folio_nr_pages(folio);
 	folio_put_refs(folio, refs);
 }
@@ -855,14 +852,15 @@ noinline int __filemap_add_folio(struct address_space *mapping,
 
 	if (!huge) {
 		int error = mem_cgroup_charge(folio, NULL, gfp);
-		VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
 		if (error)
 			return error;
 		charged = true;
-		xas_set_order(&xas, index, folio_order(folio));
-		nr = folio_nr_pages(folio);
 	}
 
+	VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
+	xas_set_order(&xas, index, folio_order(folio));
+	nr = folio_nr_pages(folio);
+
 	gfp &= GFP_RECLAIM_MASK;
 	folio_ref_add(folio, nr);
 	folio->mapping = mapping;
@@ -2040,7 +2038,7 @@ unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
 		int idx = folio_batch_count(fbatch) - 1;
 
 		folio = fbatch->folios[idx];
-		if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
+		if (!xa_is_value(folio))
 			nr = folio_nr_pages(folio);
 		*start = indices[idx] + nr;
 	}
@@ -2104,7 +2102,7 @@ put:
 		int idx = folio_batch_count(fbatch) - 1;
 
 		folio = fbatch->folios[idx];
-		if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
+		if (!xa_is_value(folio))
 			nr = folio_nr_pages(folio);
 		*start = indices[idx] + nr;
 	}
@@ -2145,9 +2143,6 @@ unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
 			continue;
 		if (!folio_batch_add(fbatch, folio)) {
 			unsigned long nr = folio_nr_pages(folio);
-
-			if (folio_test_hugetlb(folio))
-				nr = 1;
 			*start = folio->index + nr;
 			goto out;
 		}
@@ -2213,9 +2208,6 @@ unsigned filemap_get_folios_contig(struct address_space *mapping,
 
 		if (!folio_batch_add(fbatch, folio)) {
 			nr = folio_nr_pages(folio);
-
-			if (folio_test_hugetlb(folio))
-				nr = 1;
 			*start = folio->index + nr;
 			goto out;
 		}
@@ -2232,10 +2224,7 @@ update_start:
 
 	if (nr) {
 		folio = fbatch->folios[nr - 1];
-		if (folio_test_hugetlb(folio))
-			*start = folio->index + 1;
-		else
-			*start = folio_next_index(folio);
+		*start = folio->index + folio_nr_pages(folio);
 	}
 out:
 	rcu_read_unlock();
@@ -2273,9 +2262,6 @@ unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
 			continue;
 		if (!folio_batch_add(fbatch, folio)) {
 			unsigned long nr = folio_nr_pages(folio);
-
-			if (folio_test_hugetlb(folio))
-				nr = 1;
 			*start = folio->index + nr;
 			goto out;
 		}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index de220e3ff8be..0aaf28ce32e5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -952,7 +952,7 @@ static long region_count(struct resv_map *resv, long f, long t)
 
 /*
  * Convert the address within this vma to the page offset within
- * the mapping, in pagecache page units; huge pages here.
+ * the mapping, huge page units here.
  */
 static pgoff_t vma_hugecache_offset(struct hstate *h,
 			struct vm_area_struct *vma, unsigned long address)
@@ -961,13 +961,6 @@ static pgoff_t vma_hugecache_offset(struct hstate *h,
 			(vma->vm_pgoff >> huge_page_order(h));
 }
 
-pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
-				     unsigned long address)
-{
-	return vma_hugecache_offset(hstate_vma(vma), vma, address);
-}
-EXPORT_SYMBOL_GPL(linear_hugepage_index);
-
 /**
  * vma_kernel_pagesize - Page size granularity for this VMA.
  * @vma: The user mapping.
@@ -2074,20 +2067,6 @@ struct address_space *hugetlb_page_mapping_lock_write(struct page *hpage)
 	return NULL;
 }
 
-pgoff_t hugetlb_basepage_index(struct page *page)
-{
-	struct page *page_head = compound_head(page);
-	pgoff_t index = page_index(page_head);
-	unsigned long compound_idx;
-
-	if (compound_order(page_head) > MAX_ORDER)
-		compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
-	else
-		compound_idx = page - page_head;
-
-	return (index << compound_order(page_head)) + compound_idx;
-}
-
 static struct folio *alloc_buddy_hugetlb_folio(struct hstate *h,
 		gfp_t gfp_mask, int nid, nodemask_t *nmask,
 		nodemask_t *node_alloc_noretry)
@@ -5772,7 +5751,7 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
 			struct vm_area_struct *vma, unsigned long address)
 {
 	struct address_space *mapping = vma->vm_file->f_mapping;
-	pgoff_t idx = vma_hugecache_offset(h, vma, address);
+	pgoff_t idx = linear_page_index(vma, address);
 	struct folio *folio;
 
 	folio = filemap_get_folio(mapping, idx);
@@ -5789,6 +5768,7 @@ int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping
 	struct hstate *h = hstate_inode(inode);
 	int err;
 
+	idx <<= huge_page_order(h);
 	__folio_set_locked(folio);
 	err = __filemap_add_folio(mapping, folio, idx, GFP_KERNEL, NULL);
 
@@ -5896,7 +5876,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
 	 * before we get page_table_lock.
 	 */
 	new_folio = false;
-	folio = filemap_lock_folio(mapping, idx);
+	folio = filemap_lock_hugetlb_folio(h, mapping, idx);
 	if (IS_ERR(folio)) {
 		size = i_size_read(mapping->host) >> huge_page_shift(h);
 		if (idx >= size)
@@ -6205,7 +6185,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		/* Just decrements count, does not deallocate */
 		vma_end_reservation(h, vma, haddr);
 
-		pagecache_folio = filemap_lock_folio(mapping, idx);
+		pagecache_folio = filemap_lock_hugetlb_folio(h, mapping, idx);
 		if (IS_ERR(pagecache_folio))
 			pagecache_folio = NULL;
 	}
@@ -6338,7 +6318,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
 
 	if (is_continue) {
 		ret = -EFAULT;
-		folio = filemap_lock_folio(mapping, idx);
+		folio = filemap_lock_hugetlb_folio(h, mapping, idx);
 		if (IS_ERR(folio))
 			goto out;
 		folio_in_pagecache = true;
diff --git a/mm/migrate.c b/mm/migrate.c
index 7d1804c4a5d9..942f8c9cd068 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -524,7 +524,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 	int expected_count;
 
 	xas_lock_irq(&xas);
-	expected_count = 2 + folio_has_private(src);
+	expected_count = folio_expected_refs(mapping, src);
 	if (!folio_ref_freeze(src, expected_count)) {
 		xas_unlock_irq(&xas);
 		return -EAGAIN;
@@ -533,11 +533,11 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 	dst->index = src->index;
 	dst->mapping = src->mapping;
 
-	folio_get(dst);
+	folio_ref_add(dst, folio_nr_pages(dst));
 
 	xas_store(&xas, dst);
 
-	folio_ref_unfreeze(src, expected_count - 1);
+	folio_ref_unfreeze(src, expected_count - folio_nr_pages(src));
 
 	xas_unlock_irq(&xas);