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Date: Fri, 3 Nov 2017 23:23:04 +0800
From: Chao Yu <chao@...nel.org>
To: Yunlong Song <yunlong.song@...wei.com>,
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
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
>>> .
>>>
>>
>
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