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Mon, 11 Nov 2019 03:40:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1573443631; bh=VoCqpZZXU+TD/E9dWol0mbo7gHobw0MXsVNk3M7Cy80=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TEHgty6qk/Mfkkc+2Pp6a01exzvM0lQDuEHQBL6y+8bPWJY2nOhL1r6IkJBWO9eMS EZc29bGAEwLm4CcHhnGdwmVBnd341YDh6YaqLEFIWBA4RoUjMjYXR9ug11Lq76jefa sG7nHIMBxRHwHq9nboitHJjyYMEK4bQIgJYoLD+o= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org C6B8060A44 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=stummala@codeaurora.org Date: Mon, 11 Nov 2019 09:10:26 +0530 From: Sahitya Tummala To: Chao Yu Message-ID: <20191111034026.GA15669@codeaurora.org> References: <1573211027-30785-1-git-send-email-stummala@codeaurora.org> <5c491884-91d3-5b85-6d49-569a8d06f3a3@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <5c491884-91d3-5b85-6d49-569a8d06f3a3@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Headers-End: 1iU0ZH-00BPS6-Fu Subject: Re: [f2fs-dev] [PATCH] f2fs: Fix deadlock under storage almost full/dirty condition X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jaegeuk Kim , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net Hi Chao, On Mon, Nov 11, 2019 at 10:51:10AM +0800, Chao Yu wrote: > On 2019/11/8 19:03, Sahitya Tummala wrote: > > There could be a potential deadlock when the storage capacity > > is almost full and theren't enough free segments available, due > > to which FG_GC is needed in the atomic commit ioctl as shown in > > the below callstack - > > > > schedule_timeout > > io_schedule_timeout > > congestion_wait > > f2fs_drop_inmem_pages_all > > f2fs_gc > > f2fs_balance_fs > > __write_node_page > > f2fs_fsync_node_pages > > f2fs_do_sync_file > > f2fs_ioctl > > > > If this inode doesn't have i_gc_failures[GC_FAILURE_ATOMIC] set, > > then it waits forever in f2fs_drop_inmem_pages_all(), for this > > atomic inode to be dropped. And the rest of the system is stuck > > waiting for sbi->gc_mutex lock, which is acquired by f2fs_balance_fs() > > in the stack above. > > I think the root cause of this issue is there is potential infinite loop in > f2fs_drop_inmem_pages_all() for the case of gc_failure is true, because once the > first inode in inode_list[ATOMIC_FILE] list didn't suffer gc failure, we will > skip dropping its in-memory cache and calling iput(), and traverse the list > again, most possibly there is the same inode in the head of that list. > I thought we are expecting for those atomic updates (without any gc failures) to be committed by doing congestion_wait() and thus retrying again. Hence, I just fixed only if we are ending up waiting for commit to happen in the atomic commit path itself, which will be a deadlock. > Could you please check below fix: > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index 7bf7b0194944..8a3a35b42a37 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -1395,6 +1395,7 @@ struct f2fs_sb_info { > unsigned int gc_mode; /* current GC state */ > unsigned int next_victim_seg[2]; /* next segment in victim section */ > /* for skip statistic */ > + unsigned int atomic_files; /* # of opened atomic file */ > unsigned long long skipped_atomic_files[2]; /* FG_GC and BG_GC */ > unsigned long long skipped_gc_rwsem; /* FG_GC only */ > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index ecd063239642..79f4b348951a 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -2047,6 +2047,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) > spin_lock(&sbi->inode_lock[ATOMIC_FILE]); > if (list_empty(&fi->inmem_ilist)) > list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]); > + sbi->atomic_files++; > spin_unlock(&sbi->inode_lock[ATOMIC_FILE]); > > /* add inode in inmem_list first and set atomic_file */ > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index 8b977bbd6822..6aa0bb693697 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -288,6 +288,8 @@ void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi, > bool gc_failure) > struct list_head *head = &sbi->inode_list[ATOMIC_FILE]; > struct inode *inode; > struct f2fs_inode_info *fi; > + unsigned int count = sbi->atomic_files; If the sbi->atomic_files decrements just after this, then the below exit condition may not work. In that case, looped will never be >= count. > + unsigned int looped = 0; > next: > spin_lock(&sbi->inode_lock[ATOMIC_FILE]); > if (list_empty(head)) { > @@ -296,22 +298,29 @@ void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi, > bool gc_failure) > } > fi = list_first_entry(head, struct f2fs_inode_info, inmem_ilist); > inode = igrab(&fi->vfs_inode); > + if (inode) > + list_move_tail(&fi->inmem_ilist, head); > spin_unlock(&sbi->inode_lock[ATOMIC_FILE]); > > if (inode) { > if (gc_failure) { > - if (fi->i_gc_failures[GC_FAILURE_ATOMIC]) > - goto drop; > - goto skip; > + if (!fi->i_gc_failures[GC_FAILURE_ATOMIC]) > + goto skip; > } > -drop: > set_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST); > f2fs_drop_inmem_pages(inode); > +skip: > iput(inode); Does this result into f2fs_evict_inode() in this context for this inode? thanks, > } > -skip: > + > congestion_wait(BLK_RW_ASYNC, HZ/50); > cond_resched(); > + > + if (gc_failure) { > + if (++looped >= count) > + return; > + } > + > goto next; > } > > @@ -334,6 +343,7 @@ void f2fs_drop_inmem_pages(struct inode *inode) > spin_lock(&sbi->inode_lock[ATOMIC_FILE]); > if (!list_empty(&fi->inmem_ilist)) > list_del_init(&fi->inmem_ilist); > + sbi->atomic_files--; > spin_unlock(&sbi->inode_lock[ATOMIC_FILE]); > } > > Thanks, -- -- Sent by a consultant of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel