f2fs: let's avoid panic if extent_tree is not created

stable inclusion
from stable-v5.10.165
commit 72009139a661ade5cb1da4239734ed02fa1cfff0
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7T7G4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=72009139a661ade5cb1da4239734ed02fa1cfff0

--------------------------------

[ Upstream commit df9d44b6 ]

This patch avoids the below panic.

pc : __lookup_extent_tree+0xd8/0x760
lr : f2fs_do_write_data_page+0x104/0x87c
sp : ffffffc010cbb3c0
x29: ffffffc010cbb3e0 x28: 0000000000000000
x27: ffffff8803e7f020 x26: ffffff8803e7ed40
x25: ffffff8803e7f020 x24: ffffffc010cbb460
x23: ffffffc010cbb480 x22: 0000000000000000
x21: 0000000000000000 x20: ffffffff22e90900
x19: 0000000000000000 x18: ffffffc010c5d080
x17: 0000000000000000 x16: 0000000000000020
x15: ffffffdb1acdbb88 x14: ffffff888759e2b0
x13: 0000000000000000 x12: ffffff802da49000
x11: 000000000a001200 x10: ffffff8803e7ed40
x9 : ffffff8023195800 x8 : ffffff802da49078
x7 : 0000000000000001 x6 : 0000000000000000
x5 : 0000000000000006 x4 : ffffffc010cbba28
x3 : 0000000000000000 x2 : ffffffc010cbb480
x1 : 0000000000000000 x0 : ffffff8803e7ed40
Call trace:
 __lookup_extent_tree+0xd8/0x760
 f2fs_do_write_data_page+0x104/0x87c
 f2fs_write_single_data_page+0x420/0xb60
 f2fs_write_cache_pages+0x418/0xb1c
 __f2fs_write_data_pages+0x428/0x58c
 f2fs_write_data_pages+0x30/0x40
 do_writepages+0x88/0x190
 __writeback_single_inode+0x48/0x448
 writeback_sb_inodes+0x468/0x9e8
 __writeback_inodes_wb+0xb8/0x2a4
 wb_writeback+0x33c/0x740
 wb_do_writeback+0x2b4/0x400
 wb_workfn+0xe4/0x34c
 process_one_work+0x24c/0x5bc
 worker_thread+0x3e8/0xa50
 kthread+0x150/0x1b4
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: Nsanglipeng <sanglipeng1@jd.com>

fs/f2fs/extent_cache.c

@@ -414,7 +414,8 @@ static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
 	struct extent_node *en;
 	bool ret = false;
 
-	f2fs_bug_on(sbi, !et);
+	if (!et)
+		return false;
 
 	trace_f2fs_lookup_extent_tree_start(inode, pgofs);