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SubjectRe: [PATCH v2] f2fs: fix out-of-free problem caused by atomic write
From
Date
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) {
+ 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@huawei.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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