jffs2: handle INO_STATE_CLEARING in jffs2_do_read_inode()

hulk inclusion
category: bugfix
bugzilla: 47446
CVE: NA
--------------------------

For inode that fails to be created midway, GC procedure may
try to GC its dnode, and in the following case BUG() will be
triggered:

CPU 0                       CPU 1
in jffs2_do_create()        in jffs2_garbage_collect_pass()

jffs2_write_dnode succeed
// for dirent
jffs2_reserve_space fail

			    inum = ic->ino
			    nlink = ic->pino_nlink (> 0)

iget_failed
  make_bad_inode
    remove_inode_hash
  iput
    jffs2_evict_inode
      jffs2_do_clear_inode
        jffs2_set_inocache_state(INO_STATE_CLEARING)

			    jffs2_gc_fetch_inode
			      jffs2_iget
			        // a new inode is created because
			        // the old inode had been unhashed
			        iget_locked
			      jffs2_do_read_inode
			        jffs2_get_ino_cache
				// assert BUG()
				f->inocache->state = INO_STATE_CLEARING

Fix it by waiting for its state changes to INO_STATE_CHECKEDABSENT.

Link: http://lists.infradead.org/pipermail/linux-mtd/2019-February/087762.htmlSigned-off-by: NHou Tao <houtao1@huawei.com>
Reviewed-by: NWei Fang <fangwei1@huawei.com>
Signed-off-by: Nzhangyi (F) <yi.zhang@huawei.com>
[cherry-pick from hulk-4.4]
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/jffs2/readinode.c

@@ -1344,6 +1344,7 @@ int jffs2_do_read_inode(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
 
 		case INO_STATE_CHECKING:
 		case INO_STATE_GC:
+		case INO_STATE_CLEARING:
 			/* If it's in either of these states, we need
 			   to wait for whoever's got it to finish and
 			   put it back. */