kernel: backport fix for non-regular inodes on f2fs

Upstream commit dda9f4b9ca ("f2fs: fix to skip verifying block address
for non-regular inode").

On 4.14, attempting to perform operations on a non-regular inode
residing on an f2fs filesystem, such rm-ing a device node, would fail
and lead to a warning / call trace in dmesg. This fix was already
applied to other kernels upstream - including 4.19, from which the patch
was taken.

More info at https://bugzilla.kernel.org/show_bug.cgi?id=202495.

Signed-off-by: Matt Merhar <mattmerhar@protonmail.com>
(cherry picked from commit ee500186a5)

target/linux/generic/backport-4.14/050-v4.19-f2fs-skip-verifying-block-address-non-regular-inode.patch

@@ -0,0 +1,69 @@
+From dda9f4b9cac6bdd2a96253b4444d7a6ce5132edb Mon Sep 17 00:00:00 2001
+From: Chao Yu <yuchao0@huawei.com>
+Date: Sat, 11 Aug 2018 23:42:09 +0800
+Subject: f2fs: fix to skip verifying block address for non-regular inode
+
+generic/184 1s ... [failed, exit status 1]- output mismatch
+    --- tests/generic/184.out	2015-01-11 16:52:27.643681072 +0800
+     QA output created by 184 - silence is golden
+    +rm: cannot remove '/mnt/f2fs/null': Bad address
+    +mknod: '/mnt/f2fs/null': Bad address
+    +chmod: cannot access '/mnt/f2fs/null': Bad address
+    +./tests/generic/184: line 36: /mnt/f2fs/null: Bad address
+    ...
+
+F2FS-fs (zram0): access invalid blkaddr:259
+EIP: f2fs_is_valid_blkaddr+0x14b/0x1b0 [f2fs]
+ f2fs_iget+0x927/0x1010 [f2fs]
+ f2fs_lookup+0x26e/0x630 [f2fs]
+ __lookup_slow+0xb3/0x140
+ lookup_slow+0x31/0x50
+ walk_component+0x185/0x1f0
+ path_lookupat+0x51/0x190
+ filename_lookup+0x7f/0x140
+ user_path_at_empty+0x36/0x40
+ vfs_statx+0x61/0xc0
+ __do_sys_stat64+0x29/0x40
+ sys_stat64+0x13/0x20
+ do_fast_syscall_32+0xaa/0x22c
+ entry_SYSENTER_32+0x53/0x86
+
+In f2fs_iget(), we will check inode's first block address, if it is valid,
+we will set FI_FIRST_BLOCK_WRITTEN flag in inode.
+
+But we should only do this for regular inode, otherwise, like special
+inode, i_addr[0] is used for storing device info instead of block address,
+it will fail checking flow obviously.
+
+So for non-regular inode, let's skip verifying address and setting flag.
+
+Signed-off-by: Chao Yu <yuchao0@huawei.com>
+Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
+---
+ fs/f2fs/inode.c | 14 ++++++++------
+ 1 file changed, 8 insertions(+), 6 deletions(-)
+
+--- a/fs/f2fs/inode.c
++++ b/fs/f2fs/inode.c
+@@ -310,13 +310,15 @@ static int do_read_inode(struct inode *i
+ 	/* get rdev by using inline_info */
+ 	__get_inode_rdev(inode, ri);
+ 
+-	err = __written_first_block(sbi, ri);
+-	if (err < 0) {
+-		f2fs_put_page(node_page, 1);
+-		return err;
++	if (S_ISREG(inode->i_mode)) {
++		err = __written_first_block(sbi, ri);
++		if (err < 0) {
++			f2fs_put_page(node_page, 1);
++			return err;
++		}
++		if (!err)
++			set_inode_flag(inode, FI_FIRST_BLOCK_WRITTEN);
+ 	}
+-	if (!err)
+-		set_inode_flag(inode, FI_FIRST_BLOCK_WRITTEN);
+ 
+ 	if (!need_inode_block_update(sbi, inode->i_ino))
+ 		fi->last_disk_size = inode->i_size;