[PATCH] btrfs: protect sb_write_pointer() with invalidate lock

[KangNing Liao <lkangn.kernel@gmail.com>]

sb_write_pointer() reads the super block from the block device page cache
using read_cache_page_gfp(). This has the same race with BLKBSZSET as the
one fixed by commit 3f29d661e568 ("btrfs: sync read disk super and set
block size").

Take the mapping invalidate lock around read_cache_page_gfp() to
serialize the read against block size changes.

Signed-off-by: KangNing Liao <lkangn.kernel@gmail.com>
---
 fs/btrfs/zoned.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 16dd87aa06f2..5f75cf0e14b9 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -131,8 +131,10 @@ static int sb_write_pointer(struct block_device *bdev, struct blk_zone *zones,
 			u64 bytenr = ALIGN_DOWN(zone_end, BTRFS_SUPER_INFO_SIZE) -
 						BTRFS_SUPER_INFO_SIZE;
 
+			filemap_invalidate_lock(mapping);
 			page[i] = read_cache_page_gfp(mapping,
 					bytenr >> PAGE_SHIFT, GFP_NOFS);
+			filemap_invalidate_unlock(mapping);
 			if (IS_ERR(page[i])) {
 				if (i == 1)
 					btrfs_release_disk_super(super[0]);
-- 
2.54.0