From: Ojaswin Mujoo Date: Fri, 15 Dec 2023 11:19:50 +0000 (+0530) Subject: ext4: fallback to complex scan if aligned scan doesn't work X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=1f6bc02f18489b9c9ea39b068d0695fb0e4567e9;p=linux.git ext4: fallback to complex scan if aligned scan doesn't work 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 Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/ee033f6dfa0a7f2934437008a909c3788233950f.1702455010.git.ojaswin@linux.ibm.com Signed-off-by: Theodore Ts'o --- diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 4b72af2908d9c..ebbceb2bac4d3 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2889,14 +2889,19 @@ repeat: 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);