[PATCH 02/11] readahead: push invalidate_lock out of page_cache_ra_unbounded

[Christoph Hellwig <hch@lst.de>]

Require the invalidate_lock to be held over calls to
page_cache_ra_unbounded instead of acquiring it in this function.

This prepares for calling page_cache_ra_unbounded from ->readahead for
fsverity read-ahead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/f2fs/file.c        |  2 ++
 fs/verity/pagecache.c |  7 +++++--
 mm/readahead.c        | 13 ++++++++-----
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index da029fed4e5a..c9b9fcdd0cae 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4418,7 +4418,9 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 	pgoff_t redirty_idx = page_idx;
 	int page_len = 0, ret = 0;
 
+	filemap_invalidate_lock_shared(mapping);
 	page_cache_ra_unbounded(&ractl, len, 0);
+	filemap_invalidate_unlock_shared(mapping);
 
 	do {
 		folio = read_cache_folio(mapping, page_idx, NULL, NULL);
diff --git a/fs/verity/pagecache.c b/fs/verity/pagecache.c
index 1a88decace53..8e0d6fde802f 100644
--- a/fs/verity/pagecache.c
+++ b/fs/verity/pagecache.c
@@ -26,10 +26,13 @@ struct page *generic_read_merkle_tree_page(struct inode *inode, pgoff_t index,
 	    (!IS_ERR(folio) && !folio_test_uptodate(folio))) {
 		DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
 
-		if (!IS_ERR(folio))
+		if (!IS_ERR(folio)) {
 			folio_put(folio);
-		else if (num_ra_pages > 1)
+		} else if (num_ra_pages > 1) {
+			filemap_invalidate_lock_shared(inode->i_mapping);
 			page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
+			filemap_invalidate_unlock_shared(inode->i_mapping);
+		}
 		folio = read_mapping_folio(inode->i_mapping, index, NULL);
 	}
 	if (IS_ERR(folio))
diff --git a/mm/readahead.c b/mm/readahead.c
index b415c9969176..25f81124beb6 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -204,7 +204,8 @@ static struct folio *ractl_alloc_folio(struct readahead_control *ractl,
  * not the function you want to call.  Use page_cache_async_readahead()
  * or page_cache_sync_readahead() instead.
  *
- * Context: File is referenced by caller.  Mutexes may be held by caller.
+ * Context: File is referenced by caller, and ractl->mapping->invalidate_lock
+ * must be held by the caller in shared mode.  Mutexes may be held by caller.
  * May sleep, but will not reenter filesystem to reclaim memory.
  */
 void page_cache_ra_unbounded(struct readahead_control *ractl,
@@ -228,9 +229,10 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 	 */
 	unsigned int nofs = memalloc_nofs_save();
 
+	lockdep_assert_held_read(&mapping->invalidate_lock);
+
 	trace_page_cache_ra_unbounded(mapping->host, index, nr_to_read,
 				      lookahead_size);
-	filemap_invalidate_lock_shared(mapping);
 	index = mapping_align_index(mapping, index);
 
 	/*
@@ -300,7 +302,6 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 	 * will then handle the error.
 	 */
 	read_pages(ractl);
-	filemap_invalidate_unlock_shared(mapping);
 	memalloc_nofs_restore(nofs);
 }
 EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
@@ -314,9 +315,9 @@ EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
 static void do_page_cache_ra(struct readahead_control *ractl,
 		unsigned long nr_to_read, unsigned long lookahead_size)
 {
-	struct inode *inode = ractl->mapping->host;
+	struct address_space *mapping = ractl->mapping;
 	unsigned long index = readahead_index(ractl);
-	loff_t isize = i_size_read(inode);
+	loff_t isize = i_size_read(mapping->host);
 	pgoff_t end_index;	/* The last page we want to read */
 
 	if (isize == 0)
@@ -329,7 +330,9 @@ static void do_page_cache_ra(struct readahead_control *ractl,
 	if (nr_to_read > end_index - index)
 		nr_to_read = end_index - index + 1;
 
+	filemap_invalidate_lock_shared(mapping);
 	page_cache_ra_unbounded(ractl, nr_to_read, lookahead_size);
+	filemap_invalidate_unlock_shared(mapping);
 }
 
 /*
-- 
2.47.3