cregit-Linux how code gets into the kernel

Release 4.15 net/rds/page.c

Directory: net/rds
/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/highmem.h>
#include <linux/gfp.h>
#include <linux/cpu.h>
#include <linux/export.h>

#include "rds.h"


struct rds_page_remainder {
	
struct page	*r_page;
	
unsigned long	r_offset;
};

static
DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders);

/**
 * rds_page_remainder_alloc - build up regions of a message.
 *
 * @scat: Scatter list for message
 * @bytes: the number of bytes needed.
 * @gfp: the waiting behaviour of the allocation
 *
 * @gfp is always ored with __GFP_HIGHMEM.  Callers must be prepared to
 * kmap the pages, etc.
 *
 * If @bytes is at least a full page then this just returns a page from
 * alloc_page().
 *
 * If @bytes is a partial page then this stores the unused region of the
 * page in a per-cpu structure.  Future partial-page allocations may be
 * satisfied from that cached region.  This lets us waste less memory on
 * small allocations with minimal complexity.  It works because the transmit
 * path passes read-only page regions down to devices.  They hold a page
 * reference until they are done with the region.
 */

int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes, gfp_t gfp) { struct rds_page_remainder *rem; unsigned long flags; struct page *page; int ret; gfp |= __GFP_HIGHMEM; /* jump straight to allocation if we're trying for a huge page */ if (bytes >= PAGE_SIZE) { page = alloc_page(gfp); if (!page) { ret = -ENOMEM; } else { sg_set_page(scat, page, PAGE_SIZE, 0); ret = 0; } goto out; } rem = &per_cpu(rds_page_remainders, get_cpu()); local_irq_save(flags); while (1) { /* avoid a tiny region getting stuck by tossing it */ if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) { rds_stats_inc(s_page_remainder_miss); __free_page(rem->r_page); rem->r_page = NULL; } /* hand out a fragment from the cached page */ if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) { sg_set_page(scat, rem->r_page, bytes, rem->r_offset); get_page(sg_page(scat)); if (rem->r_offset != 0) rds_stats_inc(s_page_remainder_hit); rem->r_offset += ALIGN(bytes, 8); if (rem->r_offset >= PAGE_SIZE) { __free_page(rem->r_page); rem->r_page = NULL; } ret = 0; break; } /* alloc if there is nothing for us to use */ local_irq_restore(flags); put_cpu(); page = alloc_page(gfp); rem = &per_cpu(rds_page_remainders, get_cpu()); local_irq_save(flags); if (!page) { ret = -ENOMEM; break; } /* did someone race to fill the remainder before us? */ if (rem->r_page) { __free_page(page); continue; } /* otherwise install our page and loop around to alloc */ rem->r_page = page; rem->r_offset = 0; } local_irq_restore(flags); put_cpu(); out: rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret, ret ? NULL : sg_page(scat), ret ? 0 : scat->offset, ret ? 0 : scat->length); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Andy Grover35498.33%266.67%
shamir rabinovitch61.67%133.33%
Total360100.00%3100.00%

EXPORT_SYMBOL_GPL(rds_page_remainder_alloc);
void rds_page_exit(void) { unsigned int cpu; for_each_possible_cpu(cpu) { struct rds_page_remainder *rem; rem = &per_cpu(rds_page_remainders, cpu); rdsdebug("cpu %u\n", cpu); if (rem->r_page) __free_page(rem->r_page); rem->r_page = NULL; } }

Contributors

PersonTokensPropCommitsCommitProp
Andy Grover4679.31%150.00%
Sebastian Andrzej Siewior1220.69%150.00%
Total58100.00%2100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Andy Grover43092.87%327.27%
Sebastian Andrzej Siewior122.59%19.09%
Tejun Heo71.51%218.18%
shamir rabinovitch61.30%19.09%
Paul Gortmaker30.65%19.09%
Américo Wang30.65%19.09%
Stephen Hemminger10.22%19.09%
Ben Hutchings10.22%19.09%
Total463100.00%11100.00%
Directory: net/rds
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