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Subject[PATCH 2/2] f2fs: fix panic during f2fs_resize_fs()
Date
f2fs_resize_fs() hangs in below callstack with testcase:
- mkfs 16GB image & mount image
- dd 8GB fileA
- dd 8GB fileB
- sync
- rm fileA
- sync
- resize filesystem to 8GB

kernel BUG at segment.c:2484!
Call Trace:
allocate_segment_by_default+0x92/0xf0 [f2fs]
f2fs_allocate_data_block+0x44b/0x7e0 [f2fs]
do_write_page+0x5a/0x110 [f2fs]
f2fs_outplace_write_data+0x55/0x100 [f2fs]
f2fs_do_write_data_page+0x392/0x850 [f2fs]
move_data_page+0x233/0x320 [f2fs]
do_garbage_collect+0x14d9/0x1660 [f2fs]
free_segment_range+0x1f7/0x310 [f2fs]
f2fs_resize_fs+0x118/0x330 [f2fs]
__f2fs_ioctl+0x487/0x3680 [f2fs]
__x64_sys_ioctl+0x8e/0xd0
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The root cause is we forgot to check that whether we have enough space
in resized filesystem to store all valid blocks in before-resizing
filesystem, then allocator will run out-of-space during block migration
in free_segment_range().

Fixes: b4b10061ef98 ("f2fs: refactor resize_fs to avoid meta updates in progress")
Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
fs/f2fs/gc.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index b3af76340026..86ba8ed0b8a7 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1977,7 +1977,20 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)

/* stop CP to protect MAIN_SEC in free_segment_range */
f2fs_lock_op(sbi);
+
+ spin_lock(&sbi->stat_lock);
+ if (shrunk_blocks + valid_user_blocks(sbi) +
+ sbi->current_reserved_blocks + sbi->unusable_block_count +
+ F2FS_OPTION(sbi).root_reserved_blocks > sbi->user_block_count)
+ err = -ENOSPC;
+ spin_unlock(&sbi->stat_lock);
+
+ if (err)
+ goto out_unlock;
+
err = free_segment_range(sbi, secs, true);
+
+out_unlock:
f2fs_unlock_op(sbi);
up_write(&sbi->gc_lock);
if (err)
--
2.29.2
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