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Date: Mon, 6 Nov 2017 09:34:10 +0800
From: Yunlong Song <yunlong.song@...wei.com>
To: Chao Yu <chao@...nel.org>, Jaegeuk Kim <jaegeuk@...nel.org>
CC: <yuchao0@...wei.com>, <yunlong.song@...oud.com>,
<miaoxie@...wei.com>, <bintian.wang@...wei.com>,
<linux-fsdevel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] f2fs: fix out-of-free problem caused by atomic write
So there is no connection between sbi->user_block_count -
valid_user_blocks(sbi)
and fi->inmem_blocks. It is sensible that sbi->user_block_count -
valid_user_blocks(sbi)
is smaller than fi->inmem_blocks.
On 2017/11/3 23:23, Chao Yu wrote:
> On 2017/11/3 22:40, Yunlong Song wrote:
>> Test:
>> Newest kernel source code from f2fs-dev
>> 1G zram with f2fs
>> 8 threads to atomic write one same file on zram
>> there are four kinds of atomic write at the same time:
>> 1 no atomic start, with atomic commit
>> 2 no atomic start, no atomic commit
>> 3 atomic start, with atomic commit
>> 4 atomic start, no atomic commit
>>
>> And I add dump_stack after the check as following,
>> + if ((sbi->user_block_count - valid_user_blocks(sbi)) <
>> + fi->inmem_blocks) {
> valid_user_blocks contains fi->inmem_blocks and all reserved new node blocks?
>
> Thanks,
>
>> + dump_stack();
>> + err = -ENOSPC;
>> + goto drop;
>> + }
>>
>> then we have:
>>
>> [ 136.237247] F2FS-fs (zram1): Unexpected flush for atomic writes: ino=4, npages=8193
>> [ 136.952469] CPU: 1 PID: 1274 Comm: atomic_t2 Not tainted 4.14.0-rc4+ #109
>> [ 136.952947] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
>> [ 136.953162] Call Trace:
>> [ 136.953162] dump_stack+0x4d/0x6e
>> [ 136.953162] commit_inmem_pages+0x258/0x270
>> [ 136.953162] ? __sb_start_write+0x48/0x80
>> [ 136.953162] ? __mnt_want_write_file+0x18/0x30
>> [ 136.953162] f2fs_ioctl+0x1025/0x1e30
>> [ 136.953162] ? up_write+0x25/0x30
>> [ 136.953162] ? f2fs_file_write_iter+0xf3/0x1e0
>> [ 136.953162] ? selinux_file_ioctl+0x114/0x1e0
>> [ 136.953162] do_vfs_ioctl+0x96/0x5a0
>> [ 136.953162] SyS_ioctl+0x79/0x90
>> [ 136.953162] ? SyS_lseek+0x87/0xb0
>> [ 136.953162] entry_SYSCALL_64_fastpath+0x13/0x94
>> [ 136.953162] RIP: 0033:0x434b97
>> [ 136.953162] RSP: 002b:00007ffc68859de8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
>> [ 136.953162] RAX: ffffffffffffffda RBX: 00000000006b78e0 RCX: 0000000000434b97
>> [ 136.953162] RDX: 00000000006b70e8 RSI: 000000000000f502 RDI: 0000000000000003
>> [ 136.953162] RBP: 0000000002000010 R08: 00000000006b70e8 R09: 00000000006b7160
>> [ 136.953162] R10: 0000000000000022 R11: 0000000000000202 R12: 00007f491a1c4010
>> [ 136.953162] R13: 0000000002001000 R14: 0000000002000000 R15: 00000000006b7938
>>
>> So I think we should add the check code.
>>
>> On 2017/11/3 12:48, Yunlong Song wrote:
>>> Because I found that it will still lead to out-of-free problem with out that check.
>>> I trace and find that it is possible that the committing date pages of the atomic
>>> file is bigger than the sbi->user_block_count - valid_user_blocks(sbi), so I add
>>> this check.
>>>
>>> On 2017/11/3 11:46, Jaegeuk Kim wrote:
>>>> On 10/30, Yunlong Song wrote:
>>>>> f2fs_balance_fs only actives once in the commit_inmem_pages, but there
>>>>> are more than one page to commit, so all the other pages will miss the
>>>>> check. This will lead to out-of-free problem when commit a very large
>>>>> file. However, we cannot do f2fs_balance_fs for each inmem page, since
>>>>> this will break atomicity. As a result, we should collect prefree
>>>>> segments if needed and stop atomic commit when there are not enough
>>>>> available blocks to write atomic pages.
>>>>>
>>>>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>>>>> ---
>>>>> fs/f2fs/f2fs.h | 1 +
>>>>> fs/f2fs/segment.c | 29 ++++++++++++++++++++++++++++-
>>>>> 2 files changed, 29 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index 13a96b8..04ce48f 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -610,6 +610,7 @@ struct f2fs_inode_info {
>>>>> struct list_head inmem_pages; /* inmemory pages managed by f2fs */
>>>>> struct task_struct *inmem_task; /* store inmemory task */
>>>>> struct mutex inmem_lock; /* lock for inmemory pages */
>>>>> + unsigned long inmem_blocks; /* inmemory blocks */
>>>>> struct extent_tree *extent_tree; /* cached extent_tree entry */
>>>>> struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */
>>>>> struct rw_semaphore i_mmap_sem;
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 46dfbca..813c110 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -210,6 +210,7 @@ void register_inmem_page(struct inode *inode, struct page *page)
>>>>> list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
>>>>> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>>>>> inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
>>>>> + fi->inmem_blocks++;
>>>>> mutex_unlock(&fi->inmem_lock);
>>>>> trace_f2fs_register_inmem_page(page, INMEM);
>>>>> @@ -221,6 +222,7 @@ static int __revoke_inmem_pages(struct inode *inode,
>>>>> struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>>> struct inmem_pages *cur, *tmp;
>>>>> int err = 0;
>>>>> + struct f2fs_inode_info *fi = F2FS_I(inode);
>>>>> list_for_each_entry_safe(cur, tmp, head, list) {
>>>>> struct page *page = cur->page;
>>>>> @@ -263,6 +265,7 @@ static int __revoke_inmem_pages(struct inode *inode,
>>>>> list_del(&cur->list);
>>>>> kmem_cache_free(inmem_entry_slab, cur);
>>>>> dec_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
>>>>> + fi->inmem_blocks--;
>>>>> }
>>>>> return err;
>>>>> }
>>>>> @@ -302,6 +305,10 @@ void drop_inmem_pages(struct inode *inode)
>>>>> if (!list_empty(&fi->inmem_ilist))
>>>>> list_del_init(&fi->inmem_ilist);
>>>>> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>>>>> + if (fi->inmem_blocks) {
>>>>> + f2fs_bug_on(sbi, 1);
>>>>> + fi->inmem_blocks = 0;
>>>>> + }
>>>>> mutex_unlock(&fi->inmem_lock);
>>>>> clear_inode_flag(inode, FI_ATOMIC_FILE);
>>>>> @@ -326,6 +333,7 @@ void drop_inmem_page(struct inode *inode, struct page *page)
>>>>> f2fs_bug_on(sbi, !cur || cur->page != page);
>>>>> list_del(&cur->list);
>>>>> + fi->inmem_blocks--;
>>>>> mutex_unlock(&fi->inmem_lock);
>>>>> dec_page_count(sbi, F2FS_INMEM_PAGES);
>>>>> @@ -410,11 +418,26 @@ int commit_inmem_pages(struct inode *inode)
>>>>> INIT_LIST_HEAD(&revoke_list);
>>>>> f2fs_balance_fs(sbi, true);
>>>>> + if (prefree_segments(sbi)
>>>>> + && has_not_enough_free_secs(sbi, 0,
>>>>> + fi->inmem_blocks / BLKS_PER_SEC(sbi))) {
>>>>> + struct cp_control cpc;
>>>>> +
>>>>> + cpc.reason = __get_cp_reason(sbi);
>>>>> + err = write_checkpoint(sbi, &cpc);
>>>>> + if (err)
>>>>> + goto drop;
>>>>> + }
>>>>> f2fs_lock_op(sbi);
>>>>> set_inode_flag(inode, FI_ATOMIC_COMMIT);
>>>>> mutex_lock(&fi->inmem_lock);
>>>>> + if ((sbi->user_block_count - valid_user_blocks(sbi)) <
>>>> What does this mean? We already allocated blocks successfully?
>>>>
>>>>> + fi->inmem_blocks) {
>>>>> + err = -ENOSPC;
>>>>> + goto drop;
>>>>> + }
>>>>> err = __commit_inmem_pages(inode, &revoke_list);
>>>>> if (err) {
>>>>> int ret;
>>>>> @@ -429,7 +452,7 @@ int commit_inmem_pages(struct inode *inode)
>>>>> ret = __revoke_inmem_pages(inode, &revoke_list, false, true);
>>>>> if (ret)
>>>>> err = ret;
>>>>> -
>>>>> +drop:
>>>>> /* drop all uncommitted pages */
>>>>> __revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>>>>> }
>>>>> @@ -437,6 +460,10 @@ int commit_inmem_pages(struct inode *inode)
>>>>> if (!list_empty(&fi->inmem_ilist))
>>>>> list_del_init(&fi->inmem_ilist);
>>>>> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>>>>> + if (fi->inmem_blocks) {
>>>>> + f2fs_bug_on(sbi, 1);
>>>>> + fi->inmem_blocks = 0;
>>>>> + }
>>>>> mutex_unlock(&fi->inmem_lock);
>>>>> clear_inode_flag(inode, FI_ATOMIC_COMMIT);
>>>>> --
>>>>> 1.8.5.2
>>>> .
>>>>
> .
>
--
Thanks,
Yunlong Song
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