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 788CD563FDD for ; Tue, 8 Sep 2026 16:15:52 +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=1788884154; cv=none; b=oSKYtNkTnf9jlqrTFz1YVH6db+6NW1EpTUcULPQSTU8gIde7IYXedUTZDjfimpqqdHRp3byOQeUtspqu8MRhc8mRyXBGD4PsXznPpUjATiV1vP32TcX5zpsiSunTbQCfe6yAIDtqCFZuiorFXdQJmNYAj7t+dYhn8wAGX2sofOE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788884154; c=relaxed/simple; bh=JSujCaC06RA1yHRYtqKF1wiV2QG6XRQ+4bdg7FzS/sY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hTIryA9fUWRAkhbcKfmTaJR5f3stVYcFyqbKL67c5mBO+dqav0q57Pxxw99FvIM6AhF5EHwFpBNbKUs3n2+xhZO+P+MKgJ+Dwb4mo2aLvoIzV0jyM0SsJdWp6k+2xw4ViZcukqDjMZ4nXid4HPe2vCutDgi2jy2+IpkFhARG/7s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bX2ddps4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bX2ddps4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 922C21F00A3F; Tue, 8 Sep 2026 16:15:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788884152; bh=DkyTmT/aHRN0NyezK4B8JxLyqO/bkd8K6uetKDkMyeI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bX2ddps4CDiV3gmQ8lYTa7KwIhCyWi9fXQlps/Jja7c9bhPBaJjkerVgKTqfrzwoH sddeFTMnm11B3ld3b0V1z27UAitJIbMBzEX4Yx7mQ1K2SyDKmy6ts8UPrFGbikjsOH 0GQr2Iw/g2URoZ9ZXcR8+k4J0NqmPgLgUBid6J4Hcmes+rz9URWdplc96niEJEKjtx ea3Sg2p35nA8YbQAgQnPrnNLm39aWXzhLYYIJM5c6C+hVMkb6qt/rtTiyydXKbPJ6M 9E/frEBxbDpzgVxblREXVk397Mge66pb3LQUAsuXkmqdpBPnh+6HBiHQ8Wnt2tcvgT 687QTIqA566fA== From: Sasha Levin To: stable@vger.kernel.org Cc: Max Kellermann , Zhang Yi , Jan Kara , Theodore Ts'o , Sasha Levin Subject: [PATCH 5.15.y 3/3] jbd2: bound shrinker scans by examined checkpoint buffers Date: Tue, 8 Sep 2026 12:15:48 -0400 Message-ID: <20260908161548.2612016-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260908161548.2612016-1-sashal@kernel.org> References: <2026090325-massive-fabulous-a27d@gregkh> <20260908161548.2612016-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Max Kellermann [ Upstream commit 15cb16496446b94e67f7abcb049b8e2c75cd3d02 ] 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: Sasha Levin --- fs/jbd2/checkpoint.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c index 36c64cf44e005..724a6ff505089 100644 --- a/fs/jbd2/checkpoint.c +++ b/fs/jbd2/checkpoint.c @@ -370,15 +370,16 @@ int jbd2_cleanup_journal_tail(journal_t *journal) /* * 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; @@ -387,13 +388,15 @@ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh, 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); @@ -414,7 +417,7 @@ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh, if (need_resched()) break; - } while (jh != last_jh); + } while (jh != last_jh && (!nr_to_scan || *nr_to_scan)); return nr_freed; } @@ -436,7 +439,6 @@ unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal, 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: @@ -469,10 +471,9 @@ unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal, 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)) @@ -528,7 +529,7 @@ void __jbd2_journal_clean_checkpoint_list(journal_t *journal, 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 -- 2.53.0