This patch adds a sysfs entry to change the folio order. Given ra_folio_order=9,
we can see page_cache_ra_order getting order=9 when we submit readahead() as
below.

==== folio_order=0 ====
 f2fs_fadvise: dev = (252,16), ino = 14, i_size = 4294967296 offset:0, len:4294967296, advise:3
 page_cache_sync_ra: dev=252:16 ino=e index=0 req_count=2048 order=0 size=0 async_size=0 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=0 order=0 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=2048 req_count=2048 order=0 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_unbounded: dev=252:16 ino=e index=2048 nr_to_read=2048 lookahead_size=0
 page_cache_sync_ra: dev=252:16 ino=e index=4096 req_count=2048 order=0 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_unbounded: dev=252:16 ino=e index=4096 nr_to_read=2048 lookahead_size=0
 page_cache_sync_ra: dev=252:16 ino=e index=6144 req_count=2048 order=0 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_unbounded: dev=252:16 ino=e index=6144 nr_to_read=2048 lookahead_size=0
 page_cache_sync_ra: dev=252:16 ino=e index=8192 req_count=2048 order=0 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_unbounded: dev=252:16 ino=e index=8192 nr_to_read=2048 lookahead_size=0
 page_cache_sync_ra: dev=252:16 ino=e index=10240 req_count=2048 order=0 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_unbounded: dev=252:16 ino=e index=10240 nr_to_read=2048 lookahead_size=0
 ...
 page_cache_ra_unbounded: dev=252:16 ino=e index=1042432 nr_to_read=2048 lookahead_size=0
 page_cache_sync_ra: dev=252:16 ino=e index=1044480 req_count=2048 order=0 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_unbounded: dev=252:16 ino=e index=1044480 nr_to_read=2048 lookahead_size=0
 page_cache_sync_ra: dev=252:16 ino=e index=1046528 req_count=2048 order=0 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_unbounded: dev=252:16 ino=e index=1046528 nr_to_read=2048 lookahead_size=0

==== folio_order=9 ====
 f2fs_fadvise: dev = (252,16), ino = 14, i_size = 4294967296 offset:0, len:4294967296, advise:3
 page_cache_sync_ra: dev=252:16 ino=e index=0 req_count=2048 order=0 size=0 async_size=0 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=0 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=2048 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=2048 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=4096 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=4096 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=6144 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=6144 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=8192 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=8192 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=10240 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=10240 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=12288 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 ...
 page_cache_sync_ra: dev=252:16 ino=e index=1040384 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=1040384 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=1042432 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=1042432 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=1044480 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=1044480 order=9 size=2048 async_size=1024 ra_pages=2048
 page_cache_sync_ra: dev=252:16 ino=e index=1046528 req_count=2048 order=9 size=2048 async_size=1024 ra_pages=2048 mmap_miss=0 prev_pos=-1
 page_cache_ra_order: dev=252:16 ino=e index=1046528 order=9 size=2048 async_size=1024 ra_pages=2048

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/data.c  | 9 +++++++++
 fs/f2fs/f2fs.h  | 3 +++
 fs/f2fs/super.c | 1 +
 fs/f2fs/sysfs.c | 9 +++++++++
 4 files changed, 22 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 1746519e403d..2813475070f8 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -4059,6 +4059,14 @@ static bool f2fs_dirty_data_folio(struct address_space *mapping,
 	return false;
 }
 
+static unsigned int f2fs_ra_folio_order(struct address_space *mapping,
+				     unsigned int order)
+{
+	if (!mapping_large_folio_support(mapping))
+		return order;
+
+	return max(order, F2FS_M_SB(mapping)->ra_folio_order);
+}
 
 static sector_t f2fs_bmap_compress(struct inode *inode, sector_t block)
 {
@@ -4377,6 +4385,7 @@ const struct address_space_operations f2fs_dblock_aops = {
 	.dirty_folio	= f2fs_dirty_data_folio,
 	.migrate_folio	= filemap_migrate_folio,
 	.invalidate_folio = f2fs_invalidate_folio,
+	.ra_folio_order	= f2fs_ra_folio_order,
 	.release_folio	= f2fs_release_folio,
 	.bmap		= f2fs_bmap,
 	.swap_activate  = f2fs_swap_activate,
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 6eeb8772cee3..c5be600fb1a6 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1926,6 +1926,9 @@ struct f2fs_sb_info {
 	/* carve out reserved_blocks from total blocks */
 	bool carve_out;
 
+	/* enable large folio for readahead. */
+	unsigned int ra_folio_order;
+
 #ifdef CONFIG_F2FS_FS_COMPRESSION
 	struct kmem_cache *page_array_slab;	/* page array entry */
 	unsigned int page_array_slab_size;	/* default page array slab size */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index ccb477086444..bae02ca96c1f 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4287,6 +4287,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
 			NAT_ENTRY_PER_BLOCK));
 	sbi->allocate_section_hint = le32_to_cpu(raw_super->section_count);
 	sbi->allocate_section_policy = ALLOCATE_FORWARD_NOHINT;
+	sbi->ra_folio_order = 0;
 	F2FS_ROOT_INO(sbi) = le32_to_cpu(raw_super->root_ino);
 	F2FS_NODE_INO(sbi) = le32_to_cpu(raw_super->node_ino);
 	F2FS_META_INO(sbi) = le32_to_cpu(raw_super->meta_ino);
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index c42f4f979d13..2537a25986a6 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -906,6 +906,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 		return count;
 	}
 
+	if (!strcmp(a->attr.name, "ra_folio_order")) {
+		if (t < 0 || t > MAX_PAGECACHE_ORDER)
+			return -EINVAL;
+		sbi->ra_folio_order = t;
+		return count;
+	}
+
 	*ui = (unsigned int)t;
 
 	return count;
@@ -1180,6 +1187,7 @@ F2FS_SBI_GENERAL_RW_ATTR(migration_window_granularity);
 F2FS_SBI_GENERAL_RW_ATTR(dir_level);
 F2FS_SBI_GENERAL_RW_ATTR(allocate_section_hint);
 F2FS_SBI_GENERAL_RW_ATTR(allocate_section_policy);
+F2FS_SBI_GENERAL_RW_ATTR(ra_folio_order);
 #ifdef CONFIG_F2FS_IOSTAT
 F2FS_SBI_GENERAL_RW_ATTR(iostat_enable);
 F2FS_SBI_GENERAL_RW_ATTR(iostat_period_ms);
@@ -1422,6 +1430,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(reserved_pin_section),
 	ATTR_LIST(allocate_section_hint),
 	ATTR_LIST(allocate_section_policy),
+	ATTR_LIST(ra_folio_order),
 	NULL,
 };
 ATTRIBUTE_GROUPS(f2fs);
-- 
2.52.0.107.ga0afd4fd5b-goog