From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B43FC433EF for ; Fri, 17 Jun 2022 10:11:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381682AbiFQKL5 (ORCPT ); Fri, 17 Jun 2022 06:11:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58382 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1381655AbiFQKL5 (ORCPT ); Fri, 17 Jun 2022 06:11:57 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E548D6A052 for ; Fri, 17 Jun 2022 03:11:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9EF81B8295F for ; Fri, 17 Jun 2022 10:11:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 051D4C3411B; Fri, 17 Jun 2022 10:11:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655460712; bh=oYi8Ldl2bG35Rak3GEdP6uQchLYMMljmq35bABNrHlk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ITv1+cjwU/dZsNumBTwCcTi6a78AMI7h/w7mSM11KfhuuFrRzUD4HT1i2q+NUV139 E1+3JgBlDRVQ8irP/567w4VHNiQ2tCZ2DcE+hJZLtejAABa67lvifMDLUFHOYaG2TJ 29EP8lzMrnkYC+XmLZKaNjnM9HkwT2xoJJDexj22gcZcxDRV80lD7IpgjrekXN6ax5 izallmfVaGiV0OeB56QVi06IrZtEIqQtget6hfBvX75E6+DlJHdBwHhutFORNwQHlg IsKYbUQZQ/jmyCCUIf4JUUbgO7+JRFMfvba+URv7CffS7+QKaDiTIkLNUFldb8IRz0 j/HifctLmVxJg== Date: Fri, 17 Jun 2022 11:11:49 +0100 From: Filipe Manana To: Naohiro Aota Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH 1/4] btrfs: ensure pages are unlocked on cow_file_range() failure Message-ID: <20220617101149.GA4041436@falcondesktop> References: <318b80987f74e1cf6bf4ab09aed2399538fc4f9e.1655391633.git.naohiro.aota@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <318b80987f74e1cf6bf4ab09aed2399538fc4f9e.1655391633.git.naohiro.aota@wdc.com> Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Jun 17, 2022 at 12:45:39AM +0900, Naohiro Aota wrote: > There is a hung_task report on zoned btrfs like below. > > https://github.com/naota/linux/issues/59 > > [ 726.328648] INFO: task rocksdb:high0:11085 blocked for more than 241 seconds. > [ 726.329839] Not tainted 5.16.0-rc1+ #1 > [ 726.330484] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 726.331603] task:rocksdb:high0 state:D stack: 0 pid:11085 ppid: 11082 flags:0x00000000 > [ 726.331608] Call Trace: > [ 726.331611] > [ 726.331614] __schedule+0x2e5/0x9d0 > [ 726.331622] schedule+0x58/0xd0 > [ 726.331626] io_schedule+0x3f/0x70 > [ 726.331629] __folio_lock+0x125/0x200 > [ 726.331634] ? find_get_entries+0x1bc/0x240 > [ 726.331638] ? filemap_invalidate_unlock_two+0x40/0x40 > [ 726.331642] truncate_inode_pages_range+0x5b2/0x770 > [ 726.331649] truncate_inode_pages_final+0x44/0x50 > [ 726.331653] btrfs_evict_inode+0x67/0x480 > [ 726.331658] evict+0xd0/0x180 > [ 726.331661] iput+0x13f/0x200 > [ 726.331664] do_unlinkat+0x1c0/0x2b0 > [ 726.331668] __x64_sys_unlink+0x23/0x30 > [ 726.331670] do_syscall_64+0x3b/0xc0 > [ 726.331674] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 726.331677] RIP: 0033:0x7fb9490a171b > [ 726.331681] RSP: 002b:00007fb943ffac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000057 > [ 726.331684] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb9490a171b > [ 726.331686] RDX: 00007fb943ffb040 RSI: 000055a6bbe6ec20 RDI: 00007fb94400d300 > [ 726.331687] RBP: 00007fb943ffad00 R08: 0000000000000000 R09: 0000000000000000 > [ 726.331688] R10: 0000000000000031 R11: 0000000000000246 R12: 00007fb943ffb000 > [ 726.331690] R13: 00007fb943ffb040 R14: 0000000000000000 R15: 00007fb943ffd260 > [ 726.331693] > > While we debug the issue, we found running fstests generic/551 on 5GB > non-zoned null_blk device in the emulated zoned mode also had a > similar hung issue. > > Also, we can reproduce the same symptom with an error injected > cow_file_range() setup. > > The hang occurs when cow_file_range() fails in the middle of > allocation. cow_file_range() called from do_allocation_zoned() can > split the give region ([start, end]) for allocation depending on > current block group usages. When btrfs can allocate bytes for one part > of the split regions but fails for the other region (e.g. because of > -ENOSPC), we return the error leaving the pages in the succeeded regions > locked. Technically, this occurs only when @unlock == 0. Otherwise, we > unlock the pages in an allocated region after creating an ordered > extent. > > Considering the callers of cow_file_range(unlock=0) won't write out > the pages, we can unlock the pages on error exit from > cow_file_range(). So, we can ensure all the pages except @locked_page > are unlocked on error case. > > In summary, cow_file_range now behaves like this: > > - page_started == 1 (return value) > - All the pages are unlocked. IO is started. > - unlock == 1 > - All the pages except @locked_page are unlocked in any case > - unlock == 0 > - On success, all the pages are locked for writing out them > - On failure, all the pages except @locked_page are unlocked > > Fixes: 42c011000963 ("btrfs: zoned: introduce dedicated data write path for zoned filesystems") > CC: stable@vger.kernel.org # 5.12+ > Signed-off-by: Naohiro Aota > --- > fs/btrfs/inode.c | 72 ++++++++++++++++++++++++++++++++++++++++++------ > 1 file changed, 64 insertions(+), 8 deletions(-) > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index 1247690e7021..0c3d9998470f 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -1134,6 +1134,28 @@ static u64 get_extent_allocation_hint(struct btrfs_inode *inode, u64 start, > * *page_started is set to one if we unlock locked_page and do everything > * required to start IO on it. It may be clean and already done with > * IO when we return. > + * > + * When unlock == 1, we unlock the pages in successfully allocated regions. > + * When unlock == 0, we leave them locked for writing them out. > + * > + * However, we unlock all the pages except @locked_page in case of failure. > + * > + * In summary, page locking state will be as follow: > + * > + * - page_started == 1 (return value) > + * - All the pages are unlocked. IO is started. > + * - Note that this can happen only on success > + * - unlock == 1 > + * - All the pages except @locked_page are unlocked in any case > + * - unlock == 0 > + * - On success, all the pages are locked for writing out them > + * - On failure, all the pages except @locked_page are unlocked > + * > + * When a failure happens in the second or later iteration of the > + * while-loop, the ordered extents created in previous iterations are kept > + * intact. So, the caller must clean them up by calling > + * btrfs_cleanup_ordered_extents(). See btrfs_run_delalloc_range() for > + * example. > */ > static noinline int cow_file_range(struct btrfs_inode *inode, > struct page *locked_page, > @@ -1143,6 +1165,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode, > struct btrfs_root *root = inode->root; > struct btrfs_fs_info *fs_info = root->fs_info; > u64 alloc_hint = 0; > + u64 orig_start = start; > u64 num_bytes; > unsigned long ram_size; > u64 cur_alloc_size = 0; > @@ -1336,18 +1359,44 @@ static noinline int cow_file_range(struct btrfs_inode *inode, > btrfs_dec_block_group_reservations(fs_info, ins.objectid); > btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1); > out_unlock: > + /* > + * Now, we have three regions to clean up, as shown below. > + * > + * |-------(1)----|---(2)---|-------------(3)----------| > + * `- orig_start `- start `- start + cur_alloc_size `- end > + * > + * We process each region below. > + */ > + > clear_bits = EXTENT_LOCKED | EXTENT_DELALLOC | EXTENT_DELALLOC_NEW | > EXTENT_DEFRAG | EXTENT_CLEAR_META_RESV; > page_ops = PAGE_UNLOCK | PAGE_START_WRITEBACK | PAGE_END_WRITEBACK; > + > /* > - * If we reserved an extent for our delalloc range (or a subrange) and > - * failed to create the respective ordered extent, then it means that > - * when we reserved the extent we decremented the extent's size from > - * the data space_info's bytes_may_use counter and incremented the > - * space_info's bytes_reserved counter by the same amount. We must make > - * sure extent_clear_unlock_delalloc() does not try to decrement again > - * the data space_info's bytes_may_use counter, therefore we do not pass > - * it the flag EXTENT_CLEAR_DATA_RESV. > + * For the range (1). We have already instantiated the ordered extents > + * for this region. They are cleaned up by > + * btrfs_cleanup_ordered_extents() in e.g, > + * btrfs_run_delalloc_range(). EXTENT_LOCKED | EXTENT_DELALLOC are > + * already cleared in the above loop. And, EXTENT_DELALLOC_NEW | > + * EXTENT_DEFRAG | EXTENT_CLEAR_META_RESV are handled by the cleanup > + * function. > + * > + * However, in case of unlock == 0, we still need to unlock the pages > + * (except @locked_page) to ensure all the pages are unlocked. > + */ > + if (!unlock && orig_start < start) > + extent_clear_unlock_delalloc(inode, orig_start, start - 1, > + locked_page, 0, page_ops); > + > + /* > + * For the range (2). If we reserved an extent for our delalloc range > + * (or a subrange) and failed to create the respective ordered extent, > + * then it means that when we reserved the extent we decremented the > + * extent's size from the data space_info's bytes_may_use counter and > + * incremented the space_info's bytes_reserved counter by the same > + * amount. We must make sure extent_clear_unlock_delalloc() does not try > + * to decrement again the data space_info's bytes_may_use counter, > + * therefore we do not pass it the flag EXTENT_CLEAR_DATA_RESV. > */ > if (extent_reserved) { > extent_clear_unlock_delalloc(inode, start, > @@ -1359,6 +1408,13 @@ static noinline int cow_file_range(struct btrfs_inode *inode, > if (start >= end) > goto out; > } > + > + /* > + * For the range (3). We never touched the region. In addition to the > + * clear_bits above, we add EXTENT_CLEAR_DATA_RESV to release the data > + * space_info's bytes_may_use counter, reserved in e.g, > + * btrfs_check_data_free_space(). This says "in .e.g.", but in fact there's only one place where we increment the bytes_may_use counter for data, which is at btrfs_check_data_free_space(). So just remove the "in e.g." part because it gives the idea that the increment/reservation can happen in more than one place. Other than that, it looks good, thanks. > + */ > extent_clear_unlock_delalloc(inode, start, end, locked_page, > clear_bits | EXTENT_CLEAR_DATA_RESV, > page_ops); > -- > 2.35.1 >