f9cd8b07a4
disk_open(). Very often this is called several times for one file. This leads to reading partition table metadata for each call. To reduce the number of disk I/O we have a simple block cache, but it is very dumb and more than half of I/O operations related to reading metadata, misses this cache. Introduce new cache layer to resolve this problem. It is independent and doesn't need initialization like bcache, and will work by default for all loaders which use the new DISK API. A successful disk_open() call to each new disk or partition produces new entry in the cache. Even more, when disk was already open, now opening of any nested partitions does not require reading top level partition table. So, if without this cache, partition table metadata was read around 20-50 times during boot, now it reads only once. This affects the booting from GPT and MBR from the UFS.
108 lines
3.6 KiB
C
108 lines
3.6 KiB
C
/*-
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* Copyright (c) 2011 Google, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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/*
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* Device descriptor for partitioned disks. To use, set the
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* d_slice and d_partition variables as follows:
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*
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* Whole disk access:
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*
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* d_slice = -1
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* d_partition = -1
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*
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* Whole MBR slice:
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*
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* d_slice = MBR slice number (typically 1..4)
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* d_partition = -1
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*
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* BSD disklabel partition within an MBR slice:
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*
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* d_slice = MBR slice number (typically 1..4)
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* d_partition = disklabel partition (typically 0..7)
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*
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* BSD disklabel partition on the true dedicated disk:
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*
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* d_slice = -1
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* d_partition = disklabel partition (typically 0..7)
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*
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* GPT partition:
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*
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* d_slice = GPT partition number (typically 1..N)
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* d_partition = 255
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*
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* For both MBR and GPT, to automatically find the 'best' slice or partition,
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* set d_slice to zero. This uses the partition type to decide which partition
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* to use according to the following list of preferences:
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*
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* FreeBSD (active)
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* FreeBSD (inactive)
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* Linux (active)
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* Linux (inactive)
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* DOS/Windows (active)
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* DOS/Windows (inactive)
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*
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* Active MBR slices (marked as bootable) are preferred over inactive. GPT
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* doesn't have the concept of active/inactive partitions. In both MBR and GPT,
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* if there are multiple slices/partitions of a given type, the first one
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* is chosen.
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*
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* The low-level disk device will typically call slice_open() from its open
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* method to interpret the disk partition tables according to the rules above.
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* This will initialize d_offset to the block offset of the start of the
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* selected partition - this offset should be added to the offset passed to
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* the device's strategy method.
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*/
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struct disk_devdesc
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{
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struct devsw *d_dev;
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int d_type;
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int d_unit;
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void *d_opendata;
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int d_slice;
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int d_partition;
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off_t d_offset;
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};
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/*
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* Parse disk metadata and initialise dev->d_offset.
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*/
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extern int disk_open(struct disk_devdesc *dev, off_t mediasize,
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u_int sectorsize);
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extern int disk_close(struct disk_devdesc *dev);
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extern void disk_cleanup(const struct devsw *d_dev);
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/*
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* Print information about slices on a disk.
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*/
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extern void disk_print(struct disk_devdesc *dev, char *prefix, int verbose);
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extern char* disk_fmtdev(struct disk_devdesc *dev);
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extern int disk_parsedev(struct disk_devdesc *dev, const char *devspec,
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const char **path);
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