From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 86538149DF4; Tue, 25 Jun 2024 09:53:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719309221; cv=none; b=cSzmSOGHb4wAKs15MQpec7gR/On+nSjWKjs1RJl6+7jgxy7Twblw4hv6fdDzxScv9PTTAC1tAy6nYPp//HQLT8mfkKHamhBGSlIqWFlGQlLhtP1avvtc93xwXfALSiYpr7HLWqLe1vYE/UwbvgaNgy4xNRKzU3AsSEhCzzEudv0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719309221; c=relaxed/simple; bh=QqHIiCpGIVkPSUZGKuQkyIOqd3SjY2GF8WVreUcUlp4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=k9HgnezdOnX/H+lXlr+YcIR5tR4YhK11QbDe8luhWUcJHtQH1kTGUIPC25AdlgUnYzye3n1xB3hi9ey1B4hULkvr2xN5TvP5ZSnMSfILPII8g0zrFLazSGKmJQGiQ6qVTxRqTow9NduFsIQcdMFySY9jEpICgafmzn2jUlXP0W0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=AVf7osTY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="AVf7osTY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10054C32781; Tue, 25 Jun 2024 09:53:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1719309221; bh=QqHIiCpGIVkPSUZGKuQkyIOqd3SjY2GF8WVreUcUlp4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AVf7osTY0EaLzW5BLzhKs+uW36Kb4xXej/3ClJnV6NO3WAJHeKh5nsrQeuDOSpZbY BmQ8WOThV3bJFp0ITfT0fTUoQZrP8VbTaTU3H47/AwaXGRsGWDQRygF64+xexhd+j6 TpwU4HtB+UH9Q1p9kWMjhvFrAnHjgfGuReVej7UU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Boris Burkov , David Sterba Subject: [PATCH 6.6 136/192] btrfs: retry block group reclaim without infinite loop Date: Tue, 25 Jun 2024 11:33:28 +0200 Message-ID: <20240625085542.380239639@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240625085537.150087723@linuxfoundation.org> References: <20240625085537.150087723@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Boris Burkov commit 4eb4e85c4f818491efc67e9373aa16b123c3f522 upstream. If inc_block_group_ro systematically fails (e.g. due to ETXTBUSY from swap) or btrfs_relocate_chunk systematically fails (from lack of space), then this worker becomes an infinite loop. At the very least, this strands the cleaner thread, but can also result in hung tasks/RCU stalls on PREEMPT_NONE kernels and if the reclaim_bgs_lock mutex is not contended. I believe the best long term fix is to manage reclaim via work queue, where we queue up a relocation on the triggering condition and re-queue on failure. In the meantime, this is an easy fix to apply to avoid the immediate pain. Fixes: 7e2718099438 ("btrfs: reinsert BGs failed to reclaim") CC: stable@vger.kernel.org # 6.6+ Signed-off-by: Boris Burkov Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/block-group.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -1788,6 +1788,7 @@ void btrfs_reclaim_bgs_work(struct work_ container_of(work, struct btrfs_fs_info, reclaim_bgs_work); struct btrfs_block_group *bg; struct btrfs_space_info *space_info; + LIST_HEAD(retry_list); if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags)) return; @@ -1924,8 +1925,11 @@ void btrfs_reclaim_bgs_work(struct work_ } next: - if (ret) - btrfs_mark_bg_to_reclaim(bg); + if (ret) { + /* Refcount held by the reclaim_bgs list after splice. */ + btrfs_get_block_group(bg); + list_add_tail(&bg->bg_list, &retry_list); + } btrfs_put_block_group(bg); mutex_unlock(&fs_info->reclaim_bgs_lock); @@ -1945,6 +1949,9 @@ next: spin_unlock(&fs_info->unused_bgs_lock); mutex_unlock(&fs_info->reclaim_bgs_lock); end: + spin_lock(&fs_info->unused_bgs_lock); + list_splice_tail(&retry_list, &fs_info->reclaim_bgs); + spin_unlock(&fs_info->unused_bgs_lock); btrfs_exclop_finish(fs_info); sb_end_write(fs_info->sb); }