f2fs: fix stale ATOMIC_WRITTEN_PAGE private pointer

When I forced to enable atomic operations intentionally, I could hit the below
panic, since we didn't clear page->private in f2fs_invalidate_page called by
file truncation.

The panic occurs due to NULL mapping having page->private.

BUG: unable to handle kernel paging request at ffffffffffffffff
IP: drop_buffers+0x38/0xe0
PGD 5d00c067
PUD 5d00e067
PMD 0
CPU: 3 PID: 1648 Comm: fsstress Tainted: G      D    OE   4.10.0+ #5
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
task: ffff9151952863c0 task.stack: ffffaaec40db4000
RIP: 0010:drop_buffers+0x38/0xe0
RSP: 0018:ffffaaec40db74c8 EFLAGS: 00010292
Call Trace:
 ? page_referenced+0x8b/0x170
 try_to_free_buffers+0xc5/0xe0
 try_to_release_page+0x49/0x50
 shrink_page_list+0x8bc/0x9f0
 shrink_inactive_list+0x1dd/0x500
 ? shrink_active_list+0x2c0/0x430
 shrink_node_memcg+0x5eb/0x7c0
 shrink_node+0xe1/0x320
 do_try_to_free_pages+0xef/0x2e0
 try_to_free_pages+0xe9/0x190
 __alloc_pages_slowpath+0x390/0xe70
 __alloc_pages_nodemask+0x291/0x2b0
 alloc_pages_current+0x95/0x140
 __page_cache_alloc+0xc4/0xe0
 pagecache_get_page+0xab/0x2a0
 grab_cache_page_write_begin+0x20/0x40
 get_read_data_page+0x2e6/0x4c0 [f2fs]
 ? f2fs_mark_inode_dirty_sync+0x16/0x30 [f2fs]
 ? truncate_data_blocks_range+0x238/0x2b0 [f2fs]
 get_lock_data_page+0x30/0x190 [f2fs]
 __exchange_data_block+0xaaf/0xf40 [f2fs]
 f2fs_fallocate+0x418/0xd00 [f2fs]
 vfs_fallocate+0x157/0x220
 SyS_fallocate+0x48/0x80

Signed-off-by: Yunlei He <heyunlei@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
[Chao Yu: use INMEM_INVALIDATE for better tracing]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1948,7 +1948,7 @@ void f2fs_invalidate_page(struct page *page, unsigned int offset,
 
 	/* This is atomic written page, keep Private */
 	if (IS_ATOMIC_WRITTEN_PAGE(page))
-		return;
+		return drop_inmem_page(inode, page);
 
 	set_page_private(page, 0);
 	ClearPagePrivate(page);

fs/f2fs/f2fs.h

@@ -789,6 +789,7 @@ enum page_type {
 	META_FLUSH,
 	INMEM,		/* the below types are used by tracepoints only. */
 	INMEM_DROP,
+	INMEM_INVALIDATE,
 	INMEM_REVOKE,
 	IPU,
 	OPU,
@@ -2251,6 +2252,7 @@ void destroy_node_manager_caches(void);
  */
 void register_inmem_page(struct inode *inode, struct page *page);
 void drop_inmem_pages(struct inode *inode);
+void drop_inmem_page(struct inode *inode, struct page *page);
 int commit_inmem_pages(struct inode *inode);
 void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need);
 void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi);

fs/f2fs/segment.c

@@ -250,6 +250,36 @@ void drop_inmem_pages(struct inode *inode)
 	stat_dec_atomic_write(inode);
 }
 
+void drop_inmem_page(struct inode *inode, struct page *page)
+{
+	struct f2fs_inode_info *fi = F2FS_I(inode);
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	struct list_head *head = &fi->inmem_pages;
+	struct inmem_pages *cur = NULL;
+
+	f2fs_bug_on(sbi, !IS_ATOMIC_WRITTEN_PAGE(page));
+
+	mutex_lock(&fi->inmem_lock);
+	list_for_each_entry(cur, head, list) {
+		if (cur->page == page)
+			break;
+	}
+
+	f2fs_bug_on(sbi, !cur || cur->page != page);
+	list_del(&cur->list);
+	mutex_unlock(&fi->inmem_lock);
+
+	dec_page_count(sbi, F2FS_INMEM_PAGES);
+	kmem_cache_free(inmem_entry_slab, cur);
+
+	ClearPageUptodate(page);
+	set_page_private(page, 0);
+	ClearPagePrivate(page);
+	f2fs_put_page(page, 0);
+
+	trace_f2fs_commit_inmem_page(page, INMEM_INVALIDATE);
+}
+
 static int __commit_inmem_pages(struct inode *inode,
 					struct list_head *revoke_list)
 {

include/trace/events/f2fs.h

@@ -15,6 +15,7 @@ TRACE_DEFINE_ENUM(META);
 TRACE_DEFINE_ENUM(META_FLUSH);
 TRACE_DEFINE_ENUM(INMEM);
 TRACE_DEFINE_ENUM(INMEM_DROP);
+TRACE_DEFINE_ENUM(INMEM_INVALIDATE);
 TRACE_DEFINE_ENUM(IPU);
 TRACE_DEFINE_ENUM(OPU);
 TRACE_DEFINE_ENUM(CURSEG_HOT_DATA);
@@ -52,6 +53,7 @@ TRACE_DEFINE_ENUM(CP_DISCARD);
 		{ META_FLUSH,	"META_FLUSH" },				\
 		{ INMEM,	"INMEM" },				\
 		{ INMEM_DROP,	"INMEM_DROP" },				\
+		{ INMEM_INVALIDATE,	"INMEM_INVALIDATE" },		\
 		{ INMEM_REVOKE,	"INMEM_REVOKE" },			\
 		{ IPU,		"IN-PLACE" },				\
 		{ OPU,		"OUT-OF-PLACE" })