There could be a scenario where f2fs_sync_node_pages gets
called during checkpoint, which in turn tries to flush
inline data and calls iput(). This results in deadlock as
iput() tries to hold cp_rwsem, which is already held at the
beginning by checkpoint->block_operations().
Call stack :
Thread A Thread B
f2fs_write_checkpoint()
- block_operations(sbi)
- f2fs_lock_all(sbi);
- down_write(&sbi->cp_rwsem);
- open()
- igrab()
- write() write inline data
- unlink()
- f2fs_sync_node_pages()
- if (is_inline_node(page))
- flush_inline_data()
- ilookup()
page = f2fs_pagecache_get_page()
if (!page)
goto iput_out;
iput_out:
-close()
-iput()
iput(inode);
- f2fs_evict_inode()
- f2fs_truncate_blocks()
- f2fs_lock_op()
- down_read(&sbi->cp_rwsem);
Fixes: 399368372ed9 ("f2fs: introduce a new global lock scheme")
Signed-off-by: Sayali Lokhande <[email protected]>
---
fs/f2fs/checkpoint.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 5ba649e..97b6378 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1219,21 +1219,19 @@ static int block_operations(struct f2fs_sb_info *sbi)
goto retry_flush_quotas;
}
-retry_flush_nodes:
down_write(&sbi->node_write);
if (get_pages(sbi, F2FS_DIRTY_NODES)) {
up_write(&sbi->node_write);
+ up_write(&sbi->node_change);
+ f2fs_unlock_all(sbi);
atomic_inc(&sbi->wb_sync_req[NODE]);
err = f2fs_sync_node_pages(sbi, &wbc, false, FS_CP_NODE_IO);
atomic_dec(&sbi->wb_sync_req[NODE]);
- if (err) {
- up_write(&sbi->node_change);
- f2fs_unlock_all(sbi);
+ if (err)
goto out;
- }
cond_resched();
- goto retry_flush_nodes;
+ goto retry_flush_quotas;
}
/*
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
On 2020/4/30 1:00, Sayali Lokhande wrote:
> There could be a scenario where f2fs_sync_node_pages gets
> called during checkpoint, which in turn tries to flush
> inline data and calls iput(). This results in deadlock as
> iput() tries to hold cp_rwsem, which is already held at the
> beginning by checkpoint->block_operations().
>
> Call stack :
>
> Thread A Thread B
> f2fs_write_checkpoint()
> - block_operations(sbi)
> - f2fs_lock_all(sbi);
> - down_write(&sbi->cp_rwsem);
>
> - open()
> - igrab()
> - write() write inline data
> - unlink()
> - f2fs_sync_node_pages()
> - if (is_inline_node(page))
> - flush_inline_data()
> - ilookup()
> page = f2fs_pagecache_get_page()
> if (!page)
> goto iput_out;
> iput_out:
> -close()
> -iput()
> iput(inode);
> - f2fs_evict_inode()
> - f2fs_truncate_blocks()
> - f2fs_lock_op()
> - down_read(&sbi->cp_rwsem);
>
> Fixes: 399368372ed9 ("f2fs: introduce a new global lock scheme")
IMO, it should be
2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data")
It brings iput() to checkpoint process for the first time.
Thanks,
> Signed-off-by: Sayali Lokhande <[email protected]>
> ---
> fs/f2fs/checkpoint.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 5ba649e..97b6378 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1219,21 +1219,19 @@ static int block_operations(struct f2fs_sb_info *sbi)
> goto retry_flush_quotas;
> }
>
> -retry_flush_nodes:
> down_write(&sbi->node_write);
>
> if (get_pages(sbi, F2FS_DIRTY_NODES)) {
> up_write(&sbi->node_write);
> + up_write(&sbi->node_change);
> + f2fs_unlock_all(sbi);
> atomic_inc(&sbi->wb_sync_req[NODE]);
> err = f2fs_sync_node_pages(sbi, &wbc, false, FS_CP_NODE_IO);
> atomic_dec(&sbi->wb_sync_req[NODE]);
> - if (err) {
> - up_write(&sbi->node_change);
> - f2fs_unlock_all(sbi);
> + if (err)
> goto out;
> - }
> cond_resched();
> - goto retry_flush_nodes;
> + goto retry_flush_quotas;
> }
>
> /*
>
On 4/30/2020 6:41 AM, Chao Yu wrote:
> On 2020/4/30 1:00, Sayali Lokhande wrote:
>> There could be a scenario where f2fs_sync_node_pages gets
>> called during checkpoint, which in turn tries to flush
>> inline data and calls iput(). This results in deadlock as
>> iput() tries to hold cp_rwsem, which is already held at the
>> beginning by checkpoint->block_operations().
>>
>> Call stack :
>>
>> Thread A Thread B
>> f2fs_write_checkpoint()
>> - block_operations(sbi)
>> - f2fs_lock_all(sbi);
>> - down_write(&sbi->cp_rwsem);
>>
>> - open()
>> - igrab()
>> - write() write inline data
>> - unlink()
>> - f2fs_sync_node_pages()
>> - if (is_inline_node(page))
>> - flush_inline_data()
>> - ilookup()
>> page = f2fs_pagecache_get_page()
>> if (!page)
>> goto iput_out;
>> iput_out:
>> -close()
>> -iput()
>> iput(inode);
>> - f2fs_evict_inode()
>> - f2fs_truncate_blocks()
>> - f2fs_lock_op()
>> - down_read(&sbi->cp_rwsem);
>>
>> Fixes: 399368372ed9 ("f2fs: introduce a new global lock scheme")
> IMO, it should be
>
> 2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data")
>
> It brings iput() to checkpoint process for the first time.
>
> Thanks,
Agreed. will update it.
>> Signed-off-by: Sayali Lokhande <[email protected]>
>> ---
>> fs/f2fs/checkpoint.c | 10 ++++------
>> 1 file changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>> index 5ba649e..97b6378 100644
>> --- a/fs/f2fs/checkpoint.c
>> +++ b/fs/f2fs/checkpoint.c
>> @@ -1219,21 +1219,19 @@ static int block_operations(struct f2fs_sb_info *sbi)
>> goto retry_flush_quotas;
>> }
>>
>> -retry_flush_nodes:
>> down_write(&sbi->node_write);
>>
>> if (get_pages(sbi, F2FS_DIRTY_NODES)) {
>> up_write(&sbi->node_write);
>> + up_write(&sbi->node_change);
>> + f2fs_unlock_all(sbi);
>> atomic_inc(&sbi->wb_sync_req[NODE]);
>> err = f2fs_sync_node_pages(sbi, &wbc, false, FS_CP_NODE_IO);
>> atomic_dec(&sbi->wb_sync_req[NODE]);
>> - if (err) {
>> - up_write(&sbi->node_change);
>> - f2fs_unlock_all(sbi);
>> + if (err)
>> goto out;
>> - }
>> cond_resched();
>> - goto retry_flush_nodes;
>> + goto retry_flush_quotas;
>> }
>>
>> /*
>>