[PATCH 2/4] filemap: find_get_entries() now updates start offset

["Vishal Moola (Oracle)" <vishal.moola@gmail.com>]

Initially, find_get_entries() was being passed in the start offset as a
value. That left the calculation of the offset to the callers. This led
to complexity in the callers trying to keep track of the index.

Now find_get_entires() takes in a pointer to the start offset and
updates the value to be directly after the last entry found. If no entry is
found, the offset is not changed. This gets rid of multiple hacky
calculations that kept track of the start offset.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 mm/filemap.c  | 15 +++++++++++++--
 mm/internal.h |  2 +-
 mm/shmem.c    | 11 ++++-------
 mm/truncate.c | 23 +++++++++--------------
 4 files changed, 27 insertions(+), 24 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index e95500b07ee9..1b8022c18dc7 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2047,11 +2047,13 @@ static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
  * shmem/tmpfs, are included in the returned array.
  *
  * Return: The number of entries which were found.
+ * Also updates @start to be positioned after the last found entry
  */
-unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
+unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
 		pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
 {
-	XA_STATE(xas, &mapping->i_pages, start);
+	XA_STATE(xas, &mapping->i_pages, *start);
+	unsigned long nr;
 	struct folio *folio;
 
 	rcu_read_lock();
@@ -2061,7 +2063,16 @@ unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
 			break;
 	}
 	rcu_read_unlock();
+	nr = folio_batch_count(fbatch);
+
+	if (nr) {
+		folio = fbatch->folios[nr - 1];
+		nr = folio_nr_pages(folio);
 
+		if (folio_test_hugetlb(folio))
+			nr = 1;
+		*start = folio->index + nr;
+	}
 	return folio_batch_count(fbatch);
 }
 
diff --git a/mm/internal.h b/mm/internal.h
index c504ac7267e0..68afdbe7106e 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -108,7 +108,7 @@ static inline void force_page_cache_readahead(struct address_space *mapping,
 
 unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
 		pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
-unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
+unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
 		pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
 void filemap_free_folio(struct address_space *mapping, struct folio *folio);
 int truncate_inode_folio(struct address_space *mapping, struct folio *folio);
diff --git a/mm/shmem.c b/mm/shmem.c
index ab4f6dfcf6bb..8240e066edfc 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -973,7 +973,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 	while (index < end) {
 		cond_resched();
 
-		if (!find_get_entries(mapping, index, end - 1, &fbatch,
+		if (!find_get_entries(mapping, &index, end - 1, &fbatch,
 				indices)) {
 			/* If all gone or hole-punch or unfalloc, we're done */
 			if (index == start || end != -1)
@@ -985,13 +985,12 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 		for (i = 0; i < folio_batch_count(&fbatch); i++) {
 			folio = fbatch.folios[i];
 
-			index = indices[i];
 			if (xa_is_value(folio)) {
 				if (unfalloc)
 					continue;
-				if (shmem_free_swap(mapping, index, folio)) {
+				if (shmem_free_swap(mapping, folio->index, folio)) {
 					/* Swap was replaced by page: retry */
-					index--;
+					index = folio->index;
 					break;
 				}
 				nr_swaps_freed++;
@@ -1004,19 +1003,17 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 				if (folio_mapping(folio) != mapping) {
 					/* Page was replaced by swap: retry */
 					folio_unlock(folio);
-					index--;
+					index = folio->index;
 					break;
 				}
 				VM_BUG_ON_FOLIO(folio_test_writeback(folio),
 						folio);
 				truncate_inode_folio(mapping, folio);
 			}
-			index = folio->index + folio_nr_pages(folio) - 1;
 			folio_unlock(folio);
 		}
 		folio_batch_remove_exceptionals(&fbatch);
 		folio_batch_release(&fbatch);
-		index++;
 	}
 
 	spin_lock_irq(&info->lock);
diff --git a/mm/truncate.c b/mm/truncate.c
index b0bd63b2359f..846ddbdb27a4 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -400,7 +400,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
 	index = start;
 	while (index < end) {
 		cond_resched();
-		if (!find_get_entries(mapping, index, end - 1, &fbatch,
+		if (!find_get_entries(mapping, &index, end - 1, &fbatch,
 				indices)) {
 			/* If all gone from start onwards, we're done */
 			if (index == start)
@@ -414,21 +414,18 @@ void truncate_inode_pages_range(struct address_space *mapping,
 			struct folio *folio = fbatch.folios[i];
 
 			/* We rely upon deletion not changing page->index */
-			index = indices[i];
-
 			if (xa_is_value(folio))
 				continue;
 
 			folio_lock(folio);
-			VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
+			VM_BUG_ON_FOLIO(!folio_contains(folio, folio->index),
+					folio);
 			folio_wait_writeback(folio);
 			truncate_inode_folio(mapping, folio);
 			folio_unlock(folio);
-			index = folio_index(folio) + folio_nr_pages(folio) - 1;
 		}
 		truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
 		folio_batch_release(&fbatch);
-		index++;
 	}
 }
 EXPORT_SYMBOL(truncate_inode_pages_range);
@@ -637,16 +634,14 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 
 	folio_batch_init(&fbatch);
 	index = start;
-	while (find_get_entries(mapping, index, end, &fbatch, indices)) {
+	while (find_get_entries(mapping, &index, end, &fbatch, indices)) {
 		for (i = 0; i < folio_batch_count(&fbatch); i++) {
 			struct folio *folio = fbatch.folios[i];
 
 			/* We rely upon deletion not changing folio->index */
-			index = indices[i];
-
 			if (xa_is_value(folio)) {
 				if (!invalidate_exceptional_entry2(mapping,
-						index, folio))
+						folio->index, folio))
 					ret = -EBUSY;
 				continue;
 			}
@@ -656,13 +651,14 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 				 * If folio is mapped, before taking its lock,
 				 * zap the rest of the file in one hit.
 				 */
-				unmap_mapping_pages(mapping, index,
-						(1 + end - index), false);
+				unmap_mapping_pages(mapping, folio->index,
+					(1 + end - folio->index), false);
 				did_range_unmap = 1;
 			}
 
 			folio_lock(folio);
-			VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
+			VM_BUG_ON_FOLIO(!folio_contains(folio, folio->index),
+					folio);
 			if (folio->mapping != mapping) {
 				folio_unlock(folio);
 				continue;
@@ -685,7 +681,6 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 		folio_batch_remove_exceptionals(&fbatch);
 		folio_batch_release(&fbatch);
 		cond_resched();
-		index++;
 	}
 	/*
 	 * For DAX we invalidate page tables after invalidating page cache.  We
-- 
2.36.1