[PATCH 1/2] mm/readahead: Add gfp_flags to ractl

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

It is currently possible for an I/O request that specifies IOCB_NOWAIT
to sleep waiting for I/O to complete in order to allocate pages for
readahead.  In order to fix that, we need the caller to be able to
specify the GFP flags to use for memory allocation in the rest of the
readahead path.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/pagemap.h |  3 +++
 mm/readahead.c          | 16 ++++++++--------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index ed02aa522263..00abb2b2f158 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -833,11 +833,13 @@ static inline int add_to_page_cache(struct page *page,
  *	  May be NULL if invoked internally by the filesystem.
  * @mapping: Readahead this filesystem object.
  * @ra: File readahead state.  May be NULL.
+ * @gfp_flags: Memory allocation flags to use.
  */
 struct readahead_control {
 	struct file *file;
 	struct address_space *mapping;
 	struct file_ra_state *ra;
+	gfp_t gfp_flags;
 /* private: use the readahead_* accessors instead */
 	pgoff_t _index;
 	unsigned int _nr_pages;
@@ -849,6 +851,7 @@ struct readahead_control {
 		.file = f,						\
 		.mapping = m,						\
 		.ra = r,						\
+		.gfp_flags = readahead_gfp_mask(m),			\
 		._index = i,						\
 	}
 
diff --git a/mm/readahead.c b/mm/readahead.c
index d589f147f4c2..58937d1fe3f7 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -177,7 +177,6 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 	struct address_space *mapping = ractl->mapping;
 	unsigned long index = readahead_index(ractl);
 	LIST_HEAD(page_pool);
-	gfp_t gfp_mask = readahead_gfp_mask(mapping);
 	unsigned long i;
 
 	/*
@@ -212,14 +211,14 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 			continue;
 		}
 
-		page = __page_cache_alloc(gfp_mask);
+		page = __page_cache_alloc(ractl->gfp_flags);
 		if (!page)
 			break;
 		if (mapping->a_ops->readpages) {
 			page->index = index + i;
 			list_add(&page->lru, &page_pool);
 		} else if (add_to_page_cache_lru(page, mapping, index + i,
-					gfp_mask) < 0) {
+					ractl->gfp_flags) < 0) {
 			put_page(page);
 			read_pages(ractl, &page_pool, true);
 			i = ractl->_index + ractl->_nr_pages - index - 1;
@@ -663,7 +662,6 @@ void readahead_expand(struct readahead_control *ractl,
 	struct address_space *mapping = ractl->mapping;
 	struct file_ra_state *ra = ractl->ra;
 	pgoff_t new_index, new_nr_pages;
-	gfp_t gfp_mask = readahead_gfp_mask(mapping);
 
 	new_index = new_start / PAGE_SIZE;
 
@@ -675,10 +673,11 @@ void readahead_expand(struct readahead_control *ractl,
 		if (page && !xa_is_value(page))
 			return; /* Page apparently present */
 
-		page = __page_cache_alloc(gfp_mask);
+		page = __page_cache_alloc(ractl->gfp_flags);
 		if (!page)
 			return;
-		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+		if (add_to_page_cache_lru(page, mapping, index,
+					  ractl->gfp_flags) < 0) {
 			put_page(page);
 			return;
 		}
@@ -698,10 +697,11 @@ void readahead_expand(struct readahead_control *ractl,
 		if (page && !xa_is_value(page))
 			return; /* Page apparently present */
 
-		page = __page_cache_alloc(gfp_mask);
+		page = __page_cache_alloc(ractl->gfp_flags);
 		if (!page)
 			return;
-		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+		if (add_to_page_cache_lru(page, mapping, index,
+					  ractl->gfp_flags) < 0) {
 			put_page(page);
 			return;
 		}
-- 
2.30.2