f2fs: allow F2FS_IPU_NOCACHE for pinned file

This patch allows f2fs to submit bios of in-place writes on pinned file.
Reviewed-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/sysfs.c

@@ -792,7 +792,8 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 	if (!strcmp(a->attr.name, "ipu_policy")) {
 		if (t >= BIT(F2FS_IPU_MAX))
 			return -EINVAL;
-		if (t && f2fs_lfs_mode(sbi))
+		/* allow F2FS_IPU_NOCACHE only for IPU in the pinned file */
+		if (f2fs_lfs_mode(sbi) && (t & ~BIT(F2FS_IPU_NOCACHE)))
 			return -EINVAL;
 		SM_I(sbi)->ipu_policy = (unsigned int)t;
 		return count;