67 lines
2.3 KiB
Diff
67 lines
2.3 KiB
Diff
From: Julia Cartwright <julia@ni.com>
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Date: Mon, 7 May 2018 08:58:57 -0500
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Subject: [PATCH] squashfs: make use of local lock in multi_cpu
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decompressor
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.1-rt3.tar.xz
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Currently, the squashfs multi_cpu decompressor makes use of
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get_cpu_ptr()/put_cpu_ptr(), which unconditionally disable preemption
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during decompression.
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Because the workload is distributed across CPUs, all CPUs can observe a
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very high wakeup latency, which has been seen to be as much as 8000us.
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Convert this decompressor to make use of a local lock, which will allow
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execution of the decompressor with preemption-enabled, but also ensure
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concurrent accesses to the percpu compressor data on the local CPU will
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be serialized.
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Cc: stable-rt@vger.kernel.org
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Reported-by: Alexander Stein <alexander.stein@systec-electronic.com>
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Tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
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Signed-off-by: Julia Cartwright <julia@ni.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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fs/squashfs/decompressor_multi_percpu.c | 16 ++++++++++++----
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1 file changed, 12 insertions(+), 4 deletions(-)
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--- a/fs/squashfs/decompressor_multi_percpu.c
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+++ b/fs/squashfs/decompressor_multi_percpu.c
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@@ -10,6 +10,7 @@
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#include <linux/slab.h>
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#include <linux/percpu.h>
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#include <linux/buffer_head.h>
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+#include <linux/locallock.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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@@ -25,6 +26,8 @@ struct squashfs_stream {
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void *stream;
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};
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+static DEFINE_LOCAL_IRQ_LOCK(stream_lock);
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+
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void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
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void *comp_opts)
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{
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@@ -79,10 +82,15 @@ int squashfs_decompress(struct squashfs_
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{
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struct squashfs_stream __percpu *percpu =
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(struct squashfs_stream __percpu *) msblk->stream;
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- struct squashfs_stream *stream = get_cpu_ptr(percpu);
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- int res = msblk->decompressor->decompress(msblk, stream->stream, bh, b,
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- offset, length, output);
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- put_cpu_ptr(stream);
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+ struct squashfs_stream *stream;
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+ int res;
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+
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+ stream = get_locked_ptr(stream_lock, percpu);
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+
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+ res = msblk->decompressor->decompress(msblk, stream->stream, bh, b,
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+ offset, length, output);
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+
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+ put_locked_ptr(stream_lock, stream);
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if (res < 0)
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ERROR("%s decompression failed, data probably corrupt\n",
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