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 47D6612EBEA; Tue, 25 Jun 2024 09:43:47 +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=1719308627; cv=none; b=P9EeR0l9O7Rn/AKGrvdEy323iM71jmf50H1U4bQGhPSDlZmoSS9J1QMHXruveGgNayScpI0Y5bpK2q+FI59J7E7WAtHKpFQdNcHKmwLVr0JzLlbgjy6LdVAhRITG+EKfoh+MeePDk2HSlmDsbSGPmw/NgV5MvRwW0BoJjJKw+DU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719308627; c=relaxed/simple; bh=YLItzNP+jA3/9R7hmnUc0TZrWimACmLNF43nM+l1RA0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Wb9TA+mpIyx5pZFsdD90a9DlvkLbFU2Skncp2CWcTbUyC7tc8J11qOpbmU1Fz5WxY5yb8AzjU/DJQuREzU0aXsX1MKW38JPsWR4eXU6VTigw4LUARoZ5Cu93tJGdPUbwBO7BlfMIw0ld6Ys9ibf2Ipyn08dDuqogwrLiwIQ+86A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CnX3O34S; 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="CnX3O34S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCFD4C32781; Tue, 25 Jun 2024 09:43:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1719308627; bh=YLItzNP+jA3/9R7hmnUc0TZrWimACmLNF43nM+l1RA0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CnX3O34SAm29Ald+BGDC1SxV9r+4Yub3aRUyeE3D7Gz7jw8VCsUgS7AO9jL0nK2TW CgPEU0L94i7Sn7zHPwY97FXDP7AOXNV7px8CoXI5mCC5y/UgXWZUseZdP4SKw9HYs6 4IwOyxx7Voo9rfipV65iGTIIMt/sPXiXwXmtvWFI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Boris Burkov , David Sterba Subject: [PATCH 6.9 185/250] btrfs: retry block group reclaim without infinite loop Date: Tue, 25 Jun 2024 11:32:23 +0200 Message-ID: <20240625085555.153064068@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240625085548.033507125@linuxfoundation.org> References: <20240625085548.033507125@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 6.9-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 @@ -1785,6 +1785,7 @@ 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; @@ -1921,8 +1922,11 @@ 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); @@ -1942,6 +1946,9 @@ 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); }