From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 09F6C2F9DA1; Fri, 4 Sep 2026 05:50:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501052; cv=none; b=XuigdPrMb+gErGwry4qqkRCb6XSd18fab7HuQX04TyfuW0F7L5M9PkkouCw63DnOffmSlyonQBXSbPumwDcsC1WKk1xCKXd64GZV5w5EsaV0/2XnOoAFH4EiOiU8CkwD9OQohXef/p20yD6wXVnH/SppTdB5VoxboV2x3y++VOk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501052; c=relaxed/simple; bh=rC+XBfGG+l7RkF6/84DysT4MnckSKx1f2PxyI5uZEu4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Z7uqyvKfxr+9iyQUKnmhXad+TJFe2Ezv58Y5wyQrMxXHRQepAPpSAJfMrPD3zUGk5/zyGAaYkFazIttk73hxheUQ3pkJXoQOKe+1bIMoTcLDT8J4+T2f+uk4/8xs+wdctgPCyKm5ZOMEJkCdKCLuhwg9CJV6hmSnleZONQtuvkE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=O+SzQ1fi; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="O+SzQ1fi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6466C1F00A3D; Fri, 4 Sep 2026 05:50:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788501050; bh=ajmHkgNZptvwt2AbPLCv5PpyEdzKXL0JczwR+Czcr3I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=O+SzQ1fih/ZUZYQr0UG1ptGdsPJH3mtIaP7QlHOlEQeuOP2+5EoKrc1gZ5OAaxBR0 wwRuF9jEXuljhH9LywIJlTCfeJtpxV3oUNlwEmwCOkNzimTMYB3C37IhYfK2H3OYtx vdhW0YIINO1HlTIhWD4PG2IWGvRDj6m8mJYjAep8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Max Kellermann , Zhang Yi , Jan Kara , Theodore Tso Subject: [PATCH 6.18 256/552] jbd2: bound shrinker scans by examined checkpoint buffers Date: Fri, 4 Sep 2026 06:56:53 +0200 Message-ID: <20260904045755.549110382@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@linuxfoundation.org> User-Agent: quilt/0.69 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Max Kellermann commit 15cb16496446b94e67f7abcb049b8e2c75cd3d02 upstream. The jbd2 shrinker currently accounts only checkpoint buffers that it successfully releases against nr_to_scan. Busy buffers therefore do not consume the scan budget. If a checkpoint transaction contains mostly busy buffers, the shrinker can scan its entire checkpoint list while holding journal->j_list_lock. Large checkpoint lists can result in excessive lock hold times and leave other CPUs spinning on j_list_lock, causing soft lockups or RCU stalls. Pass nr_to_scan into journal_shrink_one_cp_list() and decrement it for every buffer examined, including busy buffers. Pass NULL from checkpoint cleanup paths so their existing full-list behavior is preserved. This restores the scan-budget semantics that existed before journal_shrink_one_cp_list() was changed to always scan a complete checkpoint list. Fixes: b98dba273a0e ("jbd2: remove journal_clean_one_cp_list()") Cc: stable@vger.kernel.org Signed-off-by: Max Kellermann Reviewed-by: Zhang Yi Reviewed-by: Jan Kara Link: https://patch.msgid.link/20260713102229.1598812-3-max.kellermann@ionos.com Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/jbd2/checkpoint.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) --- a/fs/jbd2/checkpoint.c +++ b/fs/jbd2/checkpoint.c @@ -358,15 +358,16 @@ int jbd2_cleanup_journal_tail(journal_t /* * journal_shrink_one_cp_list * - * Find all the written-back checkpoint buffers in the given list - * and try to release them. If the whole transaction is released, set - * the 'released' parameter. Return the number of released checkpointed - * buffers. + * Find written-back checkpoint buffers in the given list and try to release + * them. If 'nr_to_scan' is set, scan at most that many buffers. If the whole + * transaction is released, set the 'released' parameter. Return the number of + * released checkpointed buffers. * * Called with j_list_lock held. */ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh, enum jbd2_shrink_type type, + unsigned long *nr_to_scan, bool *released) { struct journal_head *last_jh; @@ -375,13 +376,15 @@ static unsigned long journal_shrink_one_ int ret; *released = false; - if (!jh) + if (!jh || (nr_to_scan && !*nr_to_scan)) return 0; last_jh = jh->b_cpprev; do { jh = next_jh; next_jh = jh->b_cpnext; + if (nr_to_scan) + (*nr_to_scan)--; if (type == JBD2_SHRINK_DESTROY) { ret = __jbd2_journal_remove_checkpoint(jh); @@ -402,7 +405,7 @@ static unsigned long journal_shrink_one_ if (need_resched()) break; - } while (jh != last_jh); + } while (jh != last_jh && (!nr_to_scan || *nr_to_scan)); return nr_freed; } @@ -424,7 +427,6 @@ unsigned long jbd2_journal_shrink_checkp tid_t first_tid = 0, last_tid = 0, next_tid = 0; tid_t tid = 0; unsigned long nr_freed = 0; - unsigned long freed; bool first_set = false; again: @@ -457,10 +459,9 @@ again: next_transaction = transaction->t_cpnext; tid = transaction->t_tid; - freed = journal_shrink_one_cp_list(transaction->t_checkpoint_list, - JBD2_SHRINK_BUSY_SKIP, &released); - nr_freed += freed; - (*nr_to_scan) -= min(*nr_to_scan, freed); + nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_list, + JBD2_SHRINK_BUSY_SKIP, + nr_to_scan, &released); if (*nr_to_scan == 0) break; if (need_resched() || spin_needbreak(&journal->j_list_lock)) @@ -516,7 +517,7 @@ void __jbd2_journal_clean_checkpoint_lis transaction = next_transaction; next_transaction = transaction->t_cpnext; journal_shrink_one_cp_list(transaction->t_checkpoint_list, - type, &released); + type, NULL, &released); /* * This function only frees up some memory if possible so we * dont have an obligation to finish processing. Bail out if