[RFC 23/23] xfs: set minimum order folio for page cache based on blocksize

[Pankaj Raghav <kernel@pankajraghav.com>]

From: Pankaj Raghav <p.raghav@samsung.com>

Enabling a block size > PAGE_SIZE is only possible if we can
ensure that the filesystem allocations for the block size is treated
atomically and we do this with the min order folio requirement for the
inode. This allows the page cache to treat this inode atomically even
if on the block layer we may treat it separately.

For instance, on x86 this enables eventual usage of block size > 4k
so long as you use a sector size set of 4k.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 fs/xfs/xfs_icache.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index aacc7eec2497..81f07503f5ca 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -73,6 +73,7 @@ xfs_inode_alloc(
 	xfs_ino_t		ino)
 {
 	struct xfs_inode	*ip;
+	int			min_order = 0;
 
 	/*
 	 * XXX: If this didn't occur in transactions, we could drop GFP_NOFAIL
@@ -88,7 +89,8 @@ xfs_inode_alloc(
 	/* VFS doesn't initialise i_mode or i_state! */
 	VFS_I(ip)->i_mode = 0;
 	VFS_I(ip)->i_state = 0;
-	mapping_set_large_folios(VFS_I(ip)->i_mapping);
+	min_order = max(min_order, ilog2(mp->m_sb.sb_blocksize) - PAGE_SHIFT);
+	mapping_set_folio_orders(VFS_I(ip)->i_mapping, min_order, MAX_PAGECACHE_ORDER);
 
 	XFS_STATS_INC(mp, vn_active);
 	ASSERT(atomic_read(&ip->i_pincount) == 0);
@@ -313,6 +315,7 @@ xfs_reinit_inode(
 	dev_t			dev = inode->i_rdev;
 	kuid_t			uid = inode->i_uid;
 	kgid_t			gid = inode->i_gid;
+	int			min_order = 0;
 
 	error = inode_init_always(mp->m_super, inode);
 
@@ -323,7 +326,8 @@ xfs_reinit_inode(
 	inode->i_rdev = dev;
 	inode->i_uid = uid;
 	inode->i_gid = gid;
-	mapping_set_large_folios(inode->i_mapping);
+	min_order = max(min_order, ilog2(mp->m_sb.sb_blocksize) - PAGE_SHIFT);
+	mapping_set_folio_orders(inode->i_mapping, min_order, MAX_PAGECACHE_ORDER);
 	return error;
 }
 
-- 
2.40.1