67 lines
2.5 KiB
Diff
67 lines
2.5 KiB
Diff
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From: Ojaswin Mujoo <ojaswin@linux.ibm.com>
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To: linux-ext4@vger.kernel.org, "Theodore Ts'o" <tytso@mit.edu>
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Cc: Ritesh Harjani <ritesh.list@gmail.com>, linux-kernel@vger.kernel.org,
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Jan Kara <jack@suse.cz>, glandvador@yahoo.com, bugzilla@eyal.emu.id.au
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Subject: [PATCH 1/1] ext4: fallback to complex scan if aligned scan doesn't work
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Date: Fri, 15 Dec 2023 16:49:50 +0530
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Message-Id: <ee033f6dfa0a7f2934437008a909c3788233950f.1702455010.git.ojaswin@linux.ibm.com>
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X-Mailer: git-send-email 2.39.3
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In-Reply-To: <cover.1702455010.git.ojaswin@linux.ibm.com>
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References: <cover.1702455010.git.ojaswin@linux.ibm.com>
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Currently in case the goal length is a multiple of stripe size we use
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ext4_mb_scan_aligned() to find the stripe size aligned physical blocks.
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In case we are not able to find any, we again go back to calling
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ext4_mb_choose_next_group() to search for a different suitable block
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group. However, since the linear search always begins from the start,
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most of the times we end up with the same BG and the cycle continues.
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With large fliesystems, the CPU can be stuck in this loop for hours
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which can slow down the whole system. Hence, until we figure out a
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better way to continue the search (rather than starting from beginning)
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in ext4_mb_choose_next_group(), lets just fallback to
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ext4_mb_complex_scan_group() in case aligned scan fails, as it is much
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more likely to find the needed blocks.
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Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
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---
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fs/ext4/mballoc.c | 21 +++++++++++++--------
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1 file changed, 13 insertions(+), 8 deletions(-)
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diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
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index d72b5e3c92ec..63f12ec02485 100644
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--- a/fs/ext4/mballoc.c
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+++ b/fs/ext4/mballoc.c
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@@ -2895,14 +2895,19 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
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ac->ac_groups_scanned++;
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if (cr == CR_POWER2_ALIGNED)
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ext4_mb_simple_scan_group(ac, &e4b);
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- else if ((cr == CR_GOAL_LEN_FAST ||
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- cr == CR_BEST_AVAIL_LEN) &&
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- sbi->s_stripe &&
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- !(ac->ac_g_ex.fe_len %
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- EXT4_B2C(sbi, sbi->s_stripe)))
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- ext4_mb_scan_aligned(ac, &e4b);
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- else
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- ext4_mb_complex_scan_group(ac, &e4b);
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+ else {
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+ bool is_stripe_aligned = sbi->s_stripe &&
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+ !(ac->ac_g_ex.fe_len %
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+ EXT4_B2C(sbi, sbi->s_stripe));
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+
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+ if ((cr == CR_GOAL_LEN_FAST ||
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+ cr == CR_BEST_AVAIL_LEN) &&
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+ is_stripe_aligned)
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+ ext4_mb_scan_aligned(ac, &e4b);
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+
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+ if (ac->ac_status == AC_STATUS_CONTINUE)
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+ ext4_mb_complex_scan_group(ac, &e4b);
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+ }
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ext4_unlock_group(sb, group);
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ext4_mb_unload_buddy(&e4b);
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--
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2.39.3
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