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Date: Sat, 7 Oct 2017 22:37:45 +0000 From: "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com> To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "stable@...r.kernel.org" <stable@...r.kernel.org> Cc: Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>, "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com> Subject: [PATCH review for 4.4 07/24] ext4: fix stripe-unaligned allocations From: Jan Kara <jack@...e.cz> [ Upstream commit d9b22cf9f5466a057f2a4f1e642b469fa9d73117 ] When a filesystem is created using: mkfs.ext4 -b 4096 -E stride=512 <dev> and we try to allocate 64MB extent, we will end up directly in ext4_mb_complex_scan_group(). This is because the request is detected as power-of-two allocation (so we start in ext4_mb_regular_allocator() with ac_criteria == 0) however the check before ext4_mb_simple_scan_group() refuses the direct buddy scan because the allocation request is too large. Since cr == 0, the check whether we should use ext4_mb_scan_aligned() fails as well and we fall back to ext4_mb_complex_scan_group(). Fix the problem by checking for upper limit on power-of-two requests directly when detecting them. Reported-by: Ross Zwisler <ross.zwisler@...ux.intel.com> Signed-off-by: Jan Kara <jack@...e.cz> Signed-off-by: Theodore Ts'o <tytso@....edu> Signed-off-by: Sasha Levin <alexander.levin@...izon.com> --- fs/ext4/mballoc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 84cd77663e1f..1ba82dc5afa3 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2136,8 +2136,10 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac) * We search using buddy data only if the order of the request * is greater than equal to the sbi_s_mb_order2_reqs * You can tune it via /sys/fs/ext4/<partition>/mb_order2_req + * We also support searching for power-of-two requests only for + * requests upto maximum buddy size we have constructed. */ - if (i >= sbi->s_mb_order2_reqs) { + if (i >= sbi->s_mb_order2_reqs && i <= sb->s_blocksize_bits + 2) { /* * This should tell if fe_len is exactly power of 2 */ @@ -2207,7 +2209,7 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac) } ac->ac_groups_scanned++; - if (cr == 0 && ac->ac_2order < sb->s_blocksize_bits+2) + if (cr == 0) ext4_mb_simple_scan_group(ac, &e4b); else if (cr == 1 && sbi->s_stripe && !(ac->ac_g_ex.fe_len % sbi->s_stripe)) -- 2.11.0
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