From: Fabian Grünbichler Date: Tue, 30 Jan 2024 12:26:35 +0000 (+0100) Subject: fix #5158: cherry-pick ext4 fix for high-CPU flush X-Git-Url: https://git.proxmox.com/?p=pve-kernel.git;a=commitdiff_plain;h=0ec9138fc00f8587e090602f5939846e1e0c5229 fix #5158: cherry-pick ext4 fix for high-CPU flush Signed-off-by: Fabian Grünbichler --- diff --git a/patches/kernel/0019-fix-5158-ext4-fallback-complex-scan.patch b/patches/kernel/0019-fix-5158-ext4-fallback-complex-scan.patch new file mode 100644 index 0000000..349e9e7 --- /dev/null +++ b/patches/kernel/0019-fix-5158-ext4-fallback-complex-scan.patch @@ -0,0 +1,66 @@ +From: Ojaswin Mujoo +To: linux-ext4@vger.kernel.org, "Theodore Ts'o" +Cc: Ritesh Harjani , linux-kernel@vger.kernel.org, + Jan Kara , glandvador@yahoo.com, bugzilla@eyal.emu.id.au +Subject: [PATCH 1/1] ext4: fallback to complex scan if aligned scan doesn't work +Date: Fri, 15 Dec 2023 16:49:50 +0530 +Message-Id: +X-Mailer: git-send-email 2.39.3 +In-Reply-To: +References: + +Currently in case the goal length is a multiple of stripe size we use +ext4_mb_scan_aligned() to find the stripe size aligned physical blocks. +In case we are not able to find any, we again go back to calling +ext4_mb_choose_next_group() to search for a different suitable block +group. However, since the linear search always begins from the start, +most of the times we end up with the same BG and the cycle continues. + +With large fliesystems, the CPU can be stuck in this loop for hours +which can slow down the whole system. Hence, until we figure out a +better way to continue the search (rather than starting from beginning) +in ext4_mb_choose_next_group(), lets just fallback to +ext4_mb_complex_scan_group() in case aligned scan fails, as it is much +more likely to find the needed blocks. + +Signed-off-by: Ojaswin Mujoo +--- + fs/ext4/mballoc.c | 21 +++++++++++++-------- + 1 file changed, 13 insertions(+), 8 deletions(-) + +diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c +index d72b5e3c92ec..63f12ec02485 100644 +--- a/fs/ext4/mballoc.c ++++ b/fs/ext4/mballoc.c +@@ -2895,14 +2895,19 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac) + ac->ac_groups_scanned++; + if (cr == CR_POWER2_ALIGNED) + ext4_mb_simple_scan_group(ac, &e4b); +- else if ((cr == CR_GOAL_LEN_FAST || +- cr == CR_BEST_AVAIL_LEN) && +- sbi->s_stripe && +- !(ac->ac_g_ex.fe_len % +- EXT4_B2C(sbi, sbi->s_stripe))) +- ext4_mb_scan_aligned(ac, &e4b); +- else +- ext4_mb_complex_scan_group(ac, &e4b); ++ else { ++ bool is_stripe_aligned = sbi->s_stripe && ++ !(ac->ac_g_ex.fe_len % ++ EXT4_B2C(sbi, sbi->s_stripe)); ++ ++ if ((cr == CR_GOAL_LEN_FAST || ++ cr == CR_BEST_AVAIL_LEN) && ++ is_stripe_aligned) ++ ext4_mb_scan_aligned(ac, &e4b); ++ ++ if (ac->ac_status == AC_STATUS_CONTINUE) ++ ext4_mb_complex_scan_group(ac, &e4b); ++ } + + ext4_unlock_group(sb, group); + ext4_mb_unload_buddy(&e4b); +-- +2.39.3 + +