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SubjectRe: [PATCH] f2fs: protect free nid operation with cp_rwsem
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Hi Jaegeuk,

On 2017/3/20 6:44, Jaegeuk Kim wrote:
> Hi Chao,
>
> On 03/17, Chao Yu wrote:
>> - f2fs_balance_fs_bg
>> - build_free_ni
>> - __build_free_nids
>> - scan_nat_page
>> - add_free_nid
>> - f2fs_create
>> - f2fs_new_inode
>> - alloc_nid
>> - remove_free_nid
>>
>> This patch uses cp_rwsem to protect free nid allocation/initialization
>> to avoid reusing allocated nid in above scenario.
>
> It looks like description doesn't match to your change below?

It looks like the problem will not happen because on_build_free_nids will stop
alloc_nid stealing one allocated nid while building free nids. Please ignore
this patch, sorry.

I found another potential case, could you please check that one?

Thanks,

>
> Thanks,
>
>>
>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>> ---
>> fs/f2fs/inode.c | 2 ++
>> fs/f2fs/segment.c | 5 ++++-
>> 2 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>> index 2520fa72b23f..f941410f994a 100644
>> --- a/fs/f2fs/inode.c
>> +++ b/fs/f2fs/inode.c
>> @@ -423,7 +423,9 @@ void f2fs_evict_inode(struct inode *inode)
>> add_ino_entry(sbi, inode->i_ino, UPDATE_INO);
>> }
>> if (is_inode_flag_set(inode, FI_FREE_NID)) {
>> + f2fs_lock_op(sbi);
>> alloc_nid_failed(sbi, inode->i_ino);
>> + f2fs_unlock_op(sbi);
>> clear_inode_flag(inode, FI_FREE_NID);
>> }
>> f2fs_bug_on(sbi, err &&
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 0bf024f62330..f85e1f443c99 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -426,8 +426,11 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
>>
>> if (!available_free_memory(sbi, FREE_NIDS))
>> try_to_free_nids(sbi, MAX_FREE_NIDS);
>> - else
>> + else {
>> + f2fs_lock_op(sbi);
>> build_free_nids(sbi, false, false);
>> + f2fs_unlock_op(sbi);
>> + }
>>
>> if (!is_idle(sbi))
>> return;
>> --
>> 2.8.2.295.g3f1c1d0
>
> .
>

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