![Nick Piggin](/assets/img/avatar_default.png)
brd is missing a flush_dcache_page. On 2nd thoughts, perhaps it is the pagecache's responsibility to flush user virtual aliases (the driver of course should flush kernel virtual mappings)... but anyway, there already exists cache flushing for one direction of transfer, so we should add the other. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
598 lines
14 KiB
C
598 lines
14 KiB
C
/*
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* Ram backed block device driver.
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*
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* Copyright (C) 2007 Nick Piggin
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* Copyright (C) 2007 Novell Inc.
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*
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* Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
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* of their respective owners.
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/major.h>
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#include <linux/blkdev.h>
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#include <linux/bio.h>
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#include <linux/highmem.h>
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#include <linux/gfp.h>
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#include <linux/radix-tree.h>
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#include <linux/buffer_head.h> /* invalidate_bh_lrus() */
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#include <asm/uaccess.h>
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#define SECTOR_SHIFT 9
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#define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
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#define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
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/*
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* Each block ramdisk device has a radix_tree brd_pages of pages that stores
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* the pages containing the block device's contents. A brd page's ->index is
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* its offset in PAGE_SIZE units. This is similar to, but in no way connected
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* with, the kernel's pagecache or buffer cache (which sit above our block
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* device).
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*/
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struct brd_device {
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int brd_number;
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int brd_refcnt;
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loff_t brd_offset;
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loff_t brd_sizelimit;
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unsigned brd_blocksize;
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struct request_queue *brd_queue;
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struct gendisk *brd_disk;
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struct list_head brd_list;
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/*
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* Backing store of pages and lock to protect it. This is the contents
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* of the block device.
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*/
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spinlock_t brd_lock;
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struct radix_tree_root brd_pages;
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};
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/*
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* Look up and return a brd's page for a given sector.
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*/
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static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
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{
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pgoff_t idx;
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struct page *page;
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/*
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* The page lifetime is protected by the fact that we have opened the
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* device node -- brd pages will never be deleted under us, so we
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* don't need any further locking or refcounting.
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*
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* This is strictly true for the radix-tree nodes as well (ie. we
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* don't actually need the rcu_read_lock()), however that is not a
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* documented feature of the radix-tree API so it is better to be
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* safe here (we don't have total exclusion from radix tree updates
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* here, only deletes).
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*/
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rcu_read_lock();
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idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
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page = radix_tree_lookup(&brd->brd_pages, idx);
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rcu_read_unlock();
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BUG_ON(page && page->index != idx);
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return page;
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}
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/*
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* Look up and return a brd's page for a given sector.
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* If one does not exist, allocate an empty page, and insert that. Then
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* return it.
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*/
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static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
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{
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pgoff_t idx;
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struct page *page;
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gfp_t gfp_flags;
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page = brd_lookup_page(brd, sector);
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if (page)
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return page;
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/*
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* Must use NOIO because we don't want to recurse back into the
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* block or filesystem layers from page reclaim.
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*
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* Cannot support XIP and highmem, because our ->direct_access
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* routine for XIP must return memory that is always addressable.
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* If XIP was reworked to use pfns and kmap throughout, this
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* restriction might be able to be lifted.
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*/
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gfp_flags = GFP_NOIO | __GFP_ZERO;
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#ifndef CONFIG_BLK_DEV_XIP
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gfp_flags |= __GFP_HIGHMEM;
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#endif
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page = alloc_page(gfp_flags);
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if (!page)
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return NULL;
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if (radix_tree_preload(GFP_NOIO)) {
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__free_page(page);
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return NULL;
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}
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spin_lock(&brd->brd_lock);
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idx = sector >> PAGE_SECTORS_SHIFT;
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if (radix_tree_insert(&brd->brd_pages, idx, page)) {
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__free_page(page);
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page = radix_tree_lookup(&brd->brd_pages, idx);
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BUG_ON(!page);
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BUG_ON(page->index != idx);
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} else
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page->index = idx;
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spin_unlock(&brd->brd_lock);
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radix_tree_preload_end();
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return page;
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}
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/*
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* Free all backing store pages and radix tree. This must only be called when
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* there are no other users of the device.
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*/
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#define FREE_BATCH 16
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static void brd_free_pages(struct brd_device *brd)
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{
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unsigned long pos = 0;
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struct page *pages[FREE_BATCH];
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int nr_pages;
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do {
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int i;
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nr_pages = radix_tree_gang_lookup(&brd->brd_pages,
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(void **)pages, pos, FREE_BATCH);
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for (i = 0; i < nr_pages; i++) {
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void *ret;
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BUG_ON(pages[i]->index < pos);
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pos = pages[i]->index;
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ret = radix_tree_delete(&brd->brd_pages, pos);
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BUG_ON(!ret || ret != pages[i]);
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__free_page(pages[i]);
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}
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pos++;
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/*
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* This assumes radix_tree_gang_lookup always returns as
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* many pages as possible. If the radix-tree code changes,
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* so will this have to.
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*/
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} while (nr_pages == FREE_BATCH);
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}
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/*
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* copy_to_brd_setup must be called before copy_to_brd. It may sleep.
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*/
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static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
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{
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
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size_t copy;
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copy = min_t(size_t, n, PAGE_SIZE - offset);
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if (!brd_insert_page(brd, sector))
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return -ENOMEM;
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if (copy < n) {
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sector += copy >> SECTOR_SHIFT;
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if (!brd_insert_page(brd, sector))
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return -ENOMEM;
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}
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return 0;
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}
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/*
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* Copy n bytes from src to the brd starting at sector. Does not sleep.
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*/
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static void copy_to_brd(struct brd_device *brd, const void *src,
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sector_t sector, size_t n)
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{
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struct page *page;
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void *dst;
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
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size_t copy;
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copy = min_t(size_t, n, PAGE_SIZE - offset);
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page = brd_lookup_page(brd, sector);
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BUG_ON(!page);
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dst = kmap_atomic(page, KM_USER1);
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memcpy(dst + offset, src, copy);
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kunmap_atomic(dst, KM_USER1);
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if (copy < n) {
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src += copy;
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sector += copy >> SECTOR_SHIFT;
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copy = n - copy;
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page = brd_lookup_page(brd, sector);
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BUG_ON(!page);
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dst = kmap_atomic(page, KM_USER1);
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memcpy(dst, src, copy);
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kunmap_atomic(dst, KM_USER1);
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}
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}
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/*
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* Copy n bytes to dst from the brd starting at sector. Does not sleep.
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*/
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static void copy_from_brd(void *dst, struct brd_device *brd,
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sector_t sector, size_t n)
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{
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struct page *page;
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void *src;
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
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size_t copy;
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copy = min_t(size_t, n, PAGE_SIZE - offset);
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page = brd_lookup_page(brd, sector);
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if (page) {
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src = kmap_atomic(page, KM_USER1);
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memcpy(dst, src + offset, copy);
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kunmap_atomic(src, KM_USER1);
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} else
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memset(dst, 0, copy);
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if (copy < n) {
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dst += copy;
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sector += copy >> SECTOR_SHIFT;
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copy = n - copy;
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page = brd_lookup_page(brd, sector);
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if (page) {
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src = kmap_atomic(page, KM_USER1);
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memcpy(dst, src, copy);
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kunmap_atomic(src, KM_USER1);
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} else
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memset(dst, 0, copy);
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}
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}
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/*
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* Process a single bvec of a bio.
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*/
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static int brd_do_bvec(struct brd_device *brd, struct page *page,
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unsigned int len, unsigned int off, int rw,
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sector_t sector)
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{
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void *mem;
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int err = 0;
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if (rw != READ) {
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err = copy_to_brd_setup(brd, sector, len);
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if (err)
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goto out;
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}
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mem = kmap_atomic(page, KM_USER0);
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if (rw == READ) {
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copy_from_brd(mem + off, brd, sector, len);
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flush_dcache_page(page);
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} else {
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flush_dcache_page(page);
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copy_to_brd(brd, mem + off, sector, len);
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}
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kunmap_atomic(mem, KM_USER0);
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out:
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return err;
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}
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static int brd_make_request(struct request_queue *q, struct bio *bio)
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{
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struct block_device *bdev = bio->bi_bdev;
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struct brd_device *brd = bdev->bd_disk->private_data;
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int rw;
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struct bio_vec *bvec;
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sector_t sector;
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int i;
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int err = -EIO;
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sector = bio->bi_sector;
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if (sector + (bio->bi_size >> SECTOR_SHIFT) >
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get_capacity(bdev->bd_disk))
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goto out;
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rw = bio_rw(bio);
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if (rw == READA)
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rw = READ;
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bio_for_each_segment(bvec, bio, i) {
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unsigned int len = bvec->bv_len;
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err = brd_do_bvec(brd, bvec->bv_page, len,
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bvec->bv_offset, rw, sector);
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if (err)
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break;
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sector += len >> SECTOR_SHIFT;
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}
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out:
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bio_endio(bio, err);
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return 0;
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}
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#ifdef CONFIG_BLK_DEV_XIP
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static int brd_direct_access (struct block_device *bdev, sector_t sector,
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void **kaddr, unsigned long *pfn)
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{
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struct brd_device *brd = bdev->bd_disk->private_data;
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struct page *page;
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if (!brd)
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return -ENODEV;
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if (sector & (PAGE_SECTORS-1))
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return -EINVAL;
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if (sector + PAGE_SECTORS > get_capacity(bdev->bd_disk))
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return -ERANGE;
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page = brd_insert_page(brd, sector);
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if (!page)
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return -ENOMEM;
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*kaddr = page_address(page);
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*pfn = page_to_pfn(page);
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return 0;
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}
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#endif
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static int brd_ioctl(struct block_device *bdev, fmode_t mode,
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unsigned int cmd, unsigned long arg)
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{
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int error;
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struct brd_device *brd = bdev->bd_disk->private_data;
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if (cmd != BLKFLSBUF)
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return -ENOTTY;
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/*
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* ram device BLKFLSBUF has special semantics, we want to actually
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* release and destroy the ramdisk data.
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*/
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mutex_lock(&bdev->bd_mutex);
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error = -EBUSY;
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if (bdev->bd_openers <= 1) {
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/*
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* Invalidate the cache first, so it isn't written
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* back to the device.
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*
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* Another thread might instantiate more buffercache here,
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* but there is not much we can do to close that race.
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*/
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invalidate_bh_lrus();
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truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
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brd_free_pages(brd);
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error = 0;
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}
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mutex_unlock(&bdev->bd_mutex);
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return error;
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}
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static struct block_device_operations brd_fops = {
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.owner = THIS_MODULE,
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.locked_ioctl = brd_ioctl,
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#ifdef CONFIG_BLK_DEV_XIP
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.direct_access = brd_direct_access,
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#endif
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};
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/*
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* And now the modules code and kernel interface.
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*/
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static int rd_nr;
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int rd_size = CONFIG_BLK_DEV_RAM_SIZE;
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static int max_part;
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static int part_shift;
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module_param(rd_nr, int, 0);
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MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
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module_param(rd_size, int, 0);
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MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
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module_param(max_part, int, 0);
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MODULE_PARM_DESC(max_part, "Maximum number of partitions per RAM disk");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
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MODULE_ALIAS("rd");
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#ifndef MODULE
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/* Legacy boot options - nonmodular */
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static int __init ramdisk_size(char *str)
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{
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rd_size = simple_strtol(str, NULL, 0);
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return 1;
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}
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static int __init ramdisk_size2(char *str)
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{
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return ramdisk_size(str);
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}
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__setup("ramdisk=", ramdisk_size);
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__setup("ramdisk_size=", ramdisk_size2);
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#endif
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/*
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* The device scheme is derived from loop.c. Keep them in synch where possible
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* (should share code eventually).
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*/
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static LIST_HEAD(brd_devices);
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static DEFINE_MUTEX(brd_devices_mutex);
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static struct brd_device *brd_alloc(int i)
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{
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struct brd_device *brd;
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struct gendisk *disk;
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brd = kzalloc(sizeof(*brd), GFP_KERNEL);
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if (!brd)
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goto out;
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brd->brd_number = i;
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spin_lock_init(&brd->brd_lock);
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INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
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brd->brd_queue = blk_alloc_queue(GFP_KERNEL);
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if (!brd->brd_queue)
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goto out_free_dev;
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blk_queue_make_request(brd->brd_queue, brd_make_request);
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blk_queue_ordered(brd->brd_queue, QUEUE_ORDERED_TAG, NULL);
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blk_queue_max_sectors(brd->brd_queue, 1024);
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blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
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disk = brd->brd_disk = alloc_disk(1 << part_shift);
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if (!disk)
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goto out_free_queue;
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disk->major = RAMDISK_MAJOR;
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disk->first_minor = i << part_shift;
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disk->fops = &brd_fops;
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disk->private_data = brd;
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disk->queue = brd->brd_queue;
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disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
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sprintf(disk->disk_name, "ram%d", i);
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set_capacity(disk, rd_size * 2);
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return brd;
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out_free_queue:
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blk_cleanup_queue(brd->brd_queue);
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out_free_dev:
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kfree(brd);
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out:
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return NULL;
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}
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static void brd_free(struct brd_device *brd)
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{
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put_disk(brd->brd_disk);
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blk_cleanup_queue(brd->brd_queue);
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brd_free_pages(brd);
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kfree(brd);
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}
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static struct brd_device *brd_init_one(int i)
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{
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struct brd_device *brd;
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list_for_each_entry(brd, &brd_devices, brd_list) {
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if (brd->brd_number == i)
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goto out;
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}
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brd = brd_alloc(i);
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if (brd) {
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add_disk(brd->brd_disk);
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list_add_tail(&brd->brd_list, &brd_devices);
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}
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out:
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return brd;
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}
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static void brd_del_one(struct brd_device *brd)
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{
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list_del(&brd->brd_list);
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del_gendisk(brd->brd_disk);
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brd_free(brd);
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}
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static struct kobject *brd_probe(dev_t dev, int *part, void *data)
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{
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struct brd_device *brd;
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struct kobject *kobj;
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mutex_lock(&brd_devices_mutex);
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brd = brd_init_one(dev & MINORMASK);
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kobj = brd ? get_disk(brd->brd_disk) : ERR_PTR(-ENOMEM);
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mutex_unlock(&brd_devices_mutex);
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*part = 0;
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return kobj;
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}
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static int __init brd_init(void)
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{
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int i, nr;
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unsigned long range;
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struct brd_device *brd, *next;
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/*
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* brd module now has a feature to instantiate underlying device
|
|
* structure on-demand, provided that there is an access dev node.
|
|
* However, this will not work well with user space tool that doesn't
|
|
* know about such "feature". In order to not break any existing
|
|
* tool, we do the following:
|
|
*
|
|
* (1) if rd_nr is specified, create that many upfront, and this
|
|
* also becomes a hard limit.
|
|
* (2) if rd_nr is not specified, create 1 rd device on module
|
|
* load, user can further extend brd device by create dev node
|
|
* themselves and have kernel automatically instantiate actual
|
|
* device on-demand.
|
|
*/
|
|
|
|
part_shift = 0;
|
|
if (max_part > 0)
|
|
part_shift = fls(max_part);
|
|
|
|
if (rd_nr > 1UL << (MINORBITS - part_shift))
|
|
return -EINVAL;
|
|
|
|
if (rd_nr) {
|
|
nr = rd_nr;
|
|
range = rd_nr;
|
|
} else {
|
|
nr = CONFIG_BLK_DEV_RAM_COUNT;
|
|
range = 1UL << (MINORBITS - part_shift);
|
|
}
|
|
|
|
if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
|
|
return -EIO;
|
|
|
|
for (i = 0; i < nr; i++) {
|
|
brd = brd_alloc(i);
|
|
if (!brd)
|
|
goto out_free;
|
|
list_add_tail(&brd->brd_list, &brd_devices);
|
|
}
|
|
|
|
/* point of no return */
|
|
|
|
list_for_each_entry(brd, &brd_devices, brd_list)
|
|
add_disk(brd->brd_disk);
|
|
|
|
blk_register_region(MKDEV(RAMDISK_MAJOR, 0), range,
|
|
THIS_MODULE, brd_probe, NULL, NULL);
|
|
|
|
printk(KERN_INFO "brd: module loaded\n");
|
|
return 0;
|
|
|
|
out_free:
|
|
list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
|
|
list_del(&brd->brd_list);
|
|
brd_free(brd);
|
|
}
|
|
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
|
|
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static void __exit brd_exit(void)
|
|
{
|
|
unsigned long range;
|
|
struct brd_device *brd, *next;
|
|
|
|
range = rd_nr ? rd_nr : 1UL << (MINORBITS - part_shift);
|
|
|
|
list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
|
|
brd_del_one(brd);
|
|
|
|
blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), range);
|
|
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
|
|
}
|
|
|
|
module_init(brd_init);
|
|
module_exit(brd_exit);
|
|
|