bda8efec5c
Replace the arbitrary calculation of an initial io struct mempool size with a constant. The code calculated the number of reserved structures based on the request size and used a "magic" multiplication constant of 4. This patch changes it to reserve a fixed number - itself still chosen quite arbitrarily. Further testing might show if there is a better number to choose. Note that if there is no memory pressure, we can still allocate an arbitrary number of "struct io" structures. One structure is enough to process the whole request. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
84 lines
1.9 KiB
C
84 lines
1.9 KiB
C
/*
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* Copyright (C) 2003 Sistina Software
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* Copyright (C) 2004 - 2008 Red Hat, Inc. All rights reserved.
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*
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* Device-Mapper low-level I/O.
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*
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* This file is released under the GPL.
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*/
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#ifndef _LINUX_DM_IO_H
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#define _LINUX_DM_IO_H
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#ifdef __KERNEL__
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#include <linux/types.h>
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struct dm_io_region {
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struct block_device *bdev;
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sector_t sector;
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sector_t count; /* If this is zero the region is ignored. */
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};
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struct page_list {
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struct page_list *next;
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struct page *page;
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};
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typedef void (*io_notify_fn)(unsigned long error, void *context);
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enum dm_io_mem_type {
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DM_IO_PAGE_LIST,/* Page list */
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DM_IO_BVEC, /* Bio vector */
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DM_IO_VMA, /* Virtual memory area */
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DM_IO_KMEM, /* Kernel memory */
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};
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struct dm_io_memory {
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enum dm_io_mem_type type;
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unsigned offset;
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union {
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struct page_list *pl;
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struct bio_vec *bvec;
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void *vma;
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void *addr;
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} ptr;
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};
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struct dm_io_notify {
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io_notify_fn fn; /* Callback for asynchronous requests */
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void *context; /* Passed to callback */
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};
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/*
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* IO request structure
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*/
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struct dm_io_client;
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struct dm_io_request {
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int bi_rw; /* READ|WRITE - not READA */
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struct dm_io_memory mem; /* Memory to use for io */
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struct dm_io_notify notify; /* Synchronous if notify.fn is NULL */
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struct dm_io_client *client; /* Client memory handler */
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};
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/*
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* For async io calls, users can alternatively use the dm_io() function below
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* and dm_io_client_create() to create private mempools for the client.
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*
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* Create/destroy may block.
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*/
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struct dm_io_client *dm_io_client_create(void);
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void dm_io_client_destroy(struct dm_io_client *client);
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/*
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* IO interface using private per-client pools.
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* Each bit in the optional 'sync_error_bits' bitset indicates whether an
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* error occurred doing io to the corresponding region.
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*/
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int dm_io(struct dm_io_request *io_req, unsigned num_regions,
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struct dm_io_region *region, unsigned long *sync_error_bits);
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#endif /* __KERNEL__ */
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#endif /* _LINUX_DM_IO_H */
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