cregit-Linux how code gets into the kernel

Release 4.11 drivers/block/brd.c

Directory: drivers/block
/*
 * Ram backed block device driver.
 *
 * Copyright (C) 2007 Nick Piggin
 * Copyright (C) 2007 Novell Inc.
 *
 * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
 * of their respective owners.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/major.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/radix-tree.h>
#include <linux/fs.h>
#include <linux/slab.h>
#ifdef CONFIG_BLK_DEV_RAM_DAX
#include <linux/pfn_t.h>
#endif

#include <linux/uaccess.h>


#define SECTOR_SHIFT		9

#define PAGE_SECTORS_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)

#define PAGE_SECTORS		(1 << PAGE_SECTORS_SHIFT)

/*
 * Each block ramdisk device has a radix_tree brd_pages of pages that stores
 * the pages containing the block device's contents. A brd page's ->index is
 * its offset in PAGE_SIZE units. This is similar to, but in no way connected
 * with, the kernel's pagecache or buffer cache (which sit above our block
 * device).
 */

struct brd_device {
	
int		brd_number;

	
struct request_queue	*brd_queue;
	
struct gendisk		*brd_disk;
	
struct list_head	brd_list;

	/*
         * Backing store of pages and lock to protect it. This is the contents
         * of the block device.
         */
	
spinlock_t		brd_lock;
	
struct radix_tree_root	brd_pages;
};

/*
 * Look up and return a brd's page for a given sector.
 */
static DEFINE_MUTEX(brd_mutex);

static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector) { pgoff_t idx; struct page *page; /* * The page lifetime is protected by the fact that we have opened the * device node -- brd pages will never be deleted under us, so we * don't need any further locking or refcounting. * * This is strictly true for the radix-tree nodes as well (ie. we * don't actually need the rcu_read_lock()), however that is not a * documented feature of the radix-tree API so it is better to be * safe here (we don't have total exclusion from radix tree updates * here, only deletes). */ rcu_read_lock(); idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */ page = radix_tree_lookup(&brd->brd_pages, idx); rcu_read_unlock(); BUG_ON(page && page->index != idx); return page; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin4164.06%120.00%
Linus Torvalds1320.31%120.00%
Andrew Morton1015.62%360.00%
Total64100.00%5100.00%

/* * Look up and return a brd's page for a given sector. * If one does not exist, allocate an empty page, and insert that. Then * return it. */
static struct page *brd_insert_page(struct brd_device *brd, sector_t sector) { pgoff_t idx; struct page *page; gfp_t gfp_flags; page = brd_lookup_page(brd, sector); if (page) return page; /* * Must use NOIO because we don't want to recurse back into the * block or filesystem layers from page reclaim. * * Cannot support DAX and highmem, because our ->direct_access * routine for DAX must return memory that is always addressable. * If DAX was reworked to use pfns and kmap throughout, this * restriction might be able to be lifted. */ gfp_flags = GFP_NOIO | __GFP_ZERO; #ifndef CONFIG_BLK_DEV_RAM_DAX gfp_flags |= __GFP_HIGHMEM; #endif page = alloc_page(gfp_flags); if (!page) return NULL; if (radix_tree_preload(GFP_NOIO)) { __free_page(page); return NULL; } spin_lock(&brd->brd_lock); idx = sector >> PAGE_SECTORS_SHIFT; page->index = idx; if (radix_tree_insert(&brd->brd_pages, idx, page)) { __free_page(page); page = radix_tree_lookup(&brd->brd_pages, idx); BUG_ON(!page); BUG_ON(page->index != idx); } spin_unlock(&brd->brd_lock); radix_tree_preload_end(); return page; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin10963.01%225.00%
Andrew Morton3821.97%225.00%
Linus Torvalds179.83%112.50%
Brian Behlendorf63.47%112.50%
Matthew Wilcox21.16%112.50%
Petr Tesarik10.58%112.50%
Total173100.00%8100.00%


static void brd_free_page(struct brd_device *brd, sector_t sector) { struct page *page; pgoff_t idx; spin_lock(&brd->brd_lock); idx = sector >> PAGE_SECTORS_SHIFT; page = radix_tree_delete(&brd->brd_pages, idx); spin_unlock(&brd->brd_lock); if (page) __free_page(page); }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin65100.00%1100.00%
Total65100.00%1100.00%


static void brd_zero_page(struct brd_device *brd, sector_t sector) { struct page *page; page = brd_lookup_page(brd, sector); if (page) clear_highpage(page); }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin37100.00%1100.00%
Total37100.00%1100.00%

/* * Free all backing store pages and radix tree. This must only be called when * there are no other users of the device. */ #define FREE_BATCH 16
static void brd_free_pages(struct brd_device *brd) { unsigned long pos = 0; struct page *pages[FREE_BATCH]; int nr_pages; do { int i; nr_pages = radix_tree_gang_lookup(&brd->brd_pages, (void **)pages, pos, FREE_BATCH); for (i = 0; i < nr_pages; i++) { void *ret; BUG_ON(pages[i]->index < pos); pos = pages[i]->index; ret = radix_tree_delete(&brd->brd_pages, pos); BUG_ON(!ret || ret != pages[i]); __free_page(pages[i]); } pos++; /* * This assumes radix_tree_gang_lookup always returns as * many pages as possible. If the radix-tree code changes, * so will this have to. */ } while (nr_pages == FREE_BATCH); }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin13093.53%150.00%
Andrew Morton96.47%150.00%
Total139100.00%2100.00%

/* * copy_to_brd_setup must be called before copy_to_brd. It may sleep. */
static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n) { unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; size_t copy; copy = min_t(size_t, n, PAGE_SIZE - offset); if (!brd_insert_page(brd, sector)) return -ENOSPC; if (copy < n) { sector += copy >> SECTOR_SHIFT; if (!brd_insert_page(brd, sector)) return -ENOSPC; } return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin7377.66%120.00%
Andrew Morton1515.96%240.00%
Linus Torvalds44.26%120.00%
Matthew Wilcox22.13%120.00%
Total94100.00%5100.00%


static void discard_from_brd(struct brd_device *brd, sector_t sector, size_t n) { while (n >= PAGE_SIZE) { /* * Don't want to actually discard pages here because * re-allocating the pages can result in writeback * deadlocks under heavy load. */ if (0) brd_free_page(brd, sector); else brd_zero_page(brd, sector); sector += PAGE_SIZE >> SECTOR_SHIFT; n -= PAGE_SIZE; } }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin55100.00%1100.00%
Total55100.00%1100.00%

/* * Copy n bytes from src to the brd starting at sector. Does not sleep. */
static void copy_to_brd(struct brd_device *brd, const void *src, sector_t sector, size_t n) { struct page *page; void *dst; unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; size_t copy; copy = min_t(size_t, n, PAGE_SIZE - offset); page = brd_lookup_page(brd, sector); BUG_ON(!page); dst = kmap_atomic(page); memcpy(dst + offset, src, copy); kunmap_atomic(dst); if (copy < n) { src += copy; sector += copy >> SECTOR_SHIFT; copy = n - copy; page = brd_lookup_page(brd, sector); BUG_ON(!page); dst = kmap_atomic(page); memcpy(dst, src, copy); kunmap_atomic(dst); } }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin8754.04%111.11%
Linus Torvalds5031.06%333.33%
Andrew Morton116.83%222.22%
Christian Bornträger74.35%111.11%
Al Viro53.11%111.11%
Russell King10.62%111.11%
Total161100.00%9100.00%

/* * Copy n bytes to dst from the brd starting at sector. Does not sleep. */
static void copy_from_brd(void *dst, struct brd_device *brd, sector_t sector, size_t n) { struct page *page; void *src; unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; size_t copy; copy = min_t(size_t, n, PAGE_SIZE - offset); page = brd_lookup_page(brd, sector); if (page) { src = kmap_atomic(page); memcpy(dst, src + offset, copy); kunmap_atomic(src); } else memset(dst, 0, copy); if (copy < n) { dst += copy; sector += copy >> SECTOR_SHIFT; copy = n - copy; page = brd_lookup_page(brd, sector); if (page) { src = kmap_atomic(page); memcpy(dst, src, copy); kunmap_atomic(src); } else memset(dst, 0, copy); } }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin13172.78%114.29%
Linus Torvalds2715.00%342.86%
Al Viro137.22%114.29%
Linus Torvalds (pre-git)95.00%228.57%
Total180100.00%7100.00%

/* * Process a single bvec of a bio. */
static int brd_do_bvec(struct brd_device *brd, struct page *page, unsigned int len, unsigned int off, bool is_write, sector_t sector) { void *mem; int err = 0; if (is_write) { err = copy_to_brd_setup(brd, sector, len); if (err) goto out; } mem = kmap_atomic(page); if (!is_write) { copy_from_brd(mem + off, brd, sector, len); flush_dcache_page(page); } else { flush_dcache_page(page); copy_to_brd(brd, mem + off, sector, len); } kunmap_atomic(mem); out: return err; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin9273.02%220.00%
Linus Torvalds (pre-git)1814.29%220.00%
Linus Torvalds75.56%220.00%
Jens Axboe43.17%110.00%
Al Viro43.17%220.00%
Michael Christie10.79%110.00%
Total126100.00%10100.00%


static blk_qc_t brd_make_request(struct request_queue *q, struct bio *bio) { struct block_device *bdev = bio->bi_bdev; struct brd_device *brd = bdev->bd_disk->private_data; struct bio_vec bvec; sector_t sector; struct bvec_iter iter; sector = bio->bi_iter.bi_sector; if (bio_end_sector(bio) > get_capacity(bdev->bd_disk)) goto io_error; if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { if (sector & ((PAGE_SIZE >> SECTOR_SHIFT) - 1) || bio->bi_iter.bi_size & ~PAGE_MASK) goto io_error; discard_from_brd(brd, sector, bio->bi_iter.bi_size); goto out; } bio_for_each_segment(bvec, bio, iter) { unsigned int len = bvec.bv_len; int err; err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset, op_is_write(bio_op(bio)), sector); if (err) goto io_error; sector += len >> SECTOR_SHIFT; } out: bio_endio(bio); return BLK_QC_T_NONE; io_error: bio_io_error(bio); return BLK_QC_T_NONE; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin13665.07%216.67%
Jan Kara2511.96%18.33%
Kent Overstreet146.70%325.00%
Christoph Hellwig146.70%18.33%
Jens Axboe104.78%216.67%
Michael Christie94.31%216.67%
Bart Van Assche10.48%18.33%
Total209100.00%12100.00%


static int brd_rw_page(struct block_device *bdev, sector_t sector, struct page *page, bool is_write) { struct brd_device *brd = bdev->bd_disk->private_data; int err = brd_do_bvec(brd, page, PAGE_SIZE, 0, is_write, sector); page_endio(page, is_write, err); return err; }

Contributors

PersonTokensPropCommitsCommitProp
Matthew Wilcox5892.06%133.33%
Jens Axboe46.35%133.33%
Kirill A. Shutemov11.59%133.33%
Total63100.00%3100.00%

#ifdef CONFIG_BLK_DEV_RAM_DAX
static long brd_direct_access(struct block_device *bdev, sector_t sector, void **kaddr, pfn_t *pfn, long size) { struct brd_device *brd = bdev->bd_disk->private_data; struct page *page; if (!brd) return -ENODEV; page = brd_insert_page(brd, sector); if (!page) return -ENOSPC; *kaddr = page_address(page); *pfn = page_to_pfn_t(page); return PAGE_SIZE; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin6675.00%116.67%
Jared Hulbert1415.91%116.67%
Dan J Williams55.68%233.33%
Matthew Wilcox33.41%233.33%
Total88100.00%6100.00%

#else #define brd_direct_access NULL #endif static const struct block_device_operations brd_fops = { .owner = THIS_MODULE, .rw_page = brd_rw_page, .direct_access = brd_direct_access, }; /* * And now the modules code and kernel interface. */ static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT; module_param(rd_nr, int, S_IRUGO); MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices"); unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE; module_param(rd_size, ulong, S_IRUGO); MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes."); static int max_part = 1; module_param(max_part, int, S_IRUGO); MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices"); MODULE_LICENSE("GPL"); MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR); MODULE_ALIAS("rd"); #ifndef MODULE /* Legacy boot options - nonmodular */
static int __init ramdisk_size(char *str) { rd_size = simple_strtol(str, NULL, 0); return 1; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin2288.00%150.00%
Linus Torvalds312.00%150.00%
Total25100.00%2100.00%

__setup("ramdisk_size=", ramdisk_size); #endif /* * The device scheme is derived from loop.c. Keep them in synch where possible * (should share code eventually). */ static LIST_HEAD(brd_devices); static DEFINE_MUTEX(brd_devices_mutex);
static struct brd_device *brd_alloc(int i) { struct brd_device *brd; struct gendisk *disk; brd = kzalloc(sizeof(*brd), GFP_KERNEL); if (!brd) goto out; brd->brd_number = i; spin_lock_init(&brd->brd_lock); INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC); brd->brd_queue = blk_alloc_queue(GFP_KERNEL); if (!brd->brd_queue) goto out_free_dev; blk_queue_make_request(brd->brd_queue, brd_make_request); blk_queue_max_hw_sectors(brd->brd_queue, 1024); blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY); /* This is so fdisk will align partitions on 4k, because of * direct_access API needing 4k alignment, returning a PFN * (This is only a problem on very small devices <= 4M, * otherwise fdisk will align on 1M. Regardless this call * is harmless) */ blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE); brd->brd_queue->limits.discard_granularity = PAGE_SIZE; blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX); brd->brd_queue->limits.discard_zeroes_data = 1; queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue); #ifdef CONFIG_BLK_DEV_RAM_DAX queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue); #endif disk = brd->brd_disk = alloc_disk(max_part); if (!disk) goto out_free_queue; disk->major = RAMDISK_MAJOR; disk->first_minor = i * max_part; disk->fops = &brd_fops; disk->private_data = brd; disk->queue = brd->brd_queue; disk->flags = GENHD_FL_EXT_DEVT; sprintf(disk->disk_name, "ram%d", i); set_capacity(disk, rd_size * 2); return brd; out_free_queue: blk_cleanup_queue(brd->brd_queue); out_free_dev: kfree(brd); out: return NULL; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin18566.55%29.09%
Andrew Morton186.47%29.09%
Boaz Harrosh155.40%29.09%
Al Viro155.40%522.73%
Toshi Kani145.04%14.55%
Linus Torvalds93.24%313.64%
Eric W. Biedermann82.88%14.55%
Linus Torvalds (pre-git)51.80%313.64%
Jens Axboe41.44%14.55%
Marcin Krol41.44%14.55%
Martin K. Petersen10.36%14.55%
Total278100.00%22100.00%


static void brd_free(struct brd_device *brd) { put_disk(brd->brd_disk); blk_cleanup_queue(brd->brd_queue); brd_free_pages(brd); kfree(brd); }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin3291.43%150.00%
Linus Torvalds (pre-git)38.57%150.00%
Total35100.00%2100.00%


static struct brd_device *brd_init_one(int i, bool *new) { struct brd_device *brd; *new = false; list_for_each_entry(brd, &brd_devices, brd_list) { if (brd->brd_number == i) goto out; } brd = brd_alloc(i); if (brd) { add_disk(brd->brd_disk); list_add_tail(&brd->brd_list, &brd_devices); } *new = true; out: return brd; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin5158.62%110.00%
Boaz Harrosh1416.09%110.00%
Linus Torvalds1112.64%330.00%
Linus Torvalds (pre-git)1011.49%440.00%
Al Viro11.15%110.00%
Total87100.00%10100.00%


static void brd_del_one(struct brd_device *brd) { list_del(&brd->brd_list); del_gendisk(brd->brd_disk); brd_free(brd); }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin2167.74%120.00%
Al Viro722.58%360.00%
Jeff Garzik39.68%120.00%
Total31100.00%5100.00%


static struct kobject *brd_probe(dev_t dev, int *part, void *data) { struct brd_device *brd; struct kobject *kobj; bool new; mutex_lock(&brd_devices_mutex); brd = brd_init_one(MINOR(dev) / max_part, &new); kobj = brd ? get_disk(brd->brd_disk) : NULL; mutex_unlock(&brd_devices_mutex); if (new) *part = 0; return kobj; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin5869.05%116.67%
Boaz Harrosh1214.29%116.67%
Peter Zijlstra67.14%116.67%
Linus Torvalds (pre-git)44.76%116.67%
Namhyung Kim33.57%116.67%
Mikulas Patocka11.19%116.67%
Total84100.00%6100.00%


static int __init brd_init(void) { struct brd_device *brd, *next; int i; /* * brd module now has a feature to instantiate underlying device * structure on-demand, provided that there is an access dev node. * * (1) if rd_nr is specified, create that many upfront. else * it defaults to CONFIG_BLK_DEV_RAM_COUNT * (2) User can further extend brd devices by create dev node themselves * and have kernel automatically instantiate actual device * on-demand. Example: * mknod /path/devnod_name b 1 X # 1 is the rd major * fdisk -l /path/devnod_name * If (X / max_part) was not already created it will be created * dynamically. */ if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) return -EIO; if (unlikely(!max_part)) max_part = 1; for (i = 0; i < rd_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), 1UL << MINORBITS, THIS_MODULE, brd_probe, NULL, NULL); pr_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"); pr_info("brd: module NOT loaded !!!\n"); return -ENOMEM; }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin7643.18%15.56%
Linus Torvalds (pre-git)4324.43%633.33%
Boaz Harrosh2614.77%15.56%
Linus Torvalds84.55%15.56%
Al Viro84.55%316.67%
Peter Zijlstra73.98%15.56%
Andrew Morton52.84%211.11%
Christoph Hellwig10.57%15.56%
Akinobu Mita10.57%15.56%
Eric W. Biedermann10.57%15.56%
Total176100.00%18100.00%


static void __exit brd_exit(void) { struct brd_device *brd, *next; list_for_each_entry_safe(brd, next, &brd_devices, brd_list) brd_del_one(brd); blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS); unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); pr_info("brd: module unloaded\n"); }

Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin2746.55%114.29%
Linus Torvalds1220.69%114.29%
Linus Torvalds (pre-git)1017.24%342.86%
Boaz Harrosh813.79%114.29%
Stephen Hemminger11.72%114.29%
Total58100.00%7100.00%

module_init(brd_init); module_exit(brd_exit);

Overall Contributors

PersonTokensPropCommitsCommitProp
Nicholas Piggin163165.63%54.85%
Linus Torvalds1676.72%98.74%
Andrew Morton1234.95%1413.59%
Linus Torvalds (pre-git)1134.55%1716.50%
Boaz Harrosh873.50%21.94%
Matthew Wilcox783.14%43.88%
Al Viro562.25%109.71%
Jan Kara281.13%21.94%
Christoph Hellwig220.89%43.88%
Jens Axboe220.89%32.91%
Jared Hulbert140.56%10.97%
Dmitriy Monakhov140.56%10.97%
Toshi Kani140.56%10.97%
Kent Overstreet140.56%32.91%
Dan J Williams130.52%21.94%
Peter Zijlstra130.52%10.97%
Michael Christie100.40%21.94%
Arnd Bergmann90.36%21.94%
Eric W. Biedermann90.36%10.97%
Stephen Hemminger70.28%10.97%
Christian Bornträger70.28%10.97%
Brian Behlendorf60.24%10.97%
Namhyung Kim50.20%21.94%
Marcin Krol40.16%10.97%
Robert P. J. Day30.12%21.94%
Tejun Heo30.12%10.97%
Jeff Garzik30.12%10.97%
Laurent Vivier20.08%10.97%
Petr Tesarik10.04%10.97%
Martin K. Petersen10.04%10.97%
Mikulas Patocka10.04%10.97%
Kirill A. Shutemov10.04%10.97%
Akinobu Mita10.04%10.97%
Russell King10.04%10.97%
Alexey Dobriyan10.04%10.97%
Bart Van Assche10.04%10.97%
Total2485100.00%103100.00%
Directory: drivers/block
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