squashfs: make use of local lock in multi_cpu decompressor
Currently, the squashfs multi_cpu decompressor makes use of get_cpu_ptr()/put_cpu_ptr(), which unconditionally disable preemption during decompression. Because the workload is distributed across CPUs, all CPUs can observe a very high wakeup latency, which has been seen to be as much as 8000us. Convert this decompressor to make use of a local lock, which will allow execution of the decompressor with preemption-enabled, but also ensure concurrent accesses to the percpu compressor data on the local CPU will be serialized. Cc: stable-rt@vger.kernel.org Reported-by: Alexander Stein <alexander.stein@systec-electronic.com> Tested-by: Alexander Stein <alexander.stein@systec-electronic.com> Signed-off-by: Julia Cartwright <julia@ni.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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@ -8,6 +8,7 @@
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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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@ -23,6 +24,8 @@ 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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void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
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void *comp_opts)
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{
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@ -77,10 +80,15 @@ int squashfs_decompress(struct squashfs_sb_info *msblk, struct buffer_head **bh,
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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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stream = get_locked_ptr(stream_lock, percpu);
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res = msblk->decompressor->decompress(msblk, stream->stream, bh, b,
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offset, length, output);
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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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