drivers/md/bcache/util.c - linux - Git at Google

 /*
  * random utiility code, for bcache but in theory not specific to bcache
  *
  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
  * Copyright 2012 Google, Inc.
  */

 #include <linux/bio.h>
 #include <linux/blkdev.h>
 #include <linux/ctype.h>
 #include <linux/debugfs.h>
 #include <linux/module.h>
 #include <linux/seq_file.h>
 #include <linux/types.h>
 #include <linux/sched/clock.h>

 #include "util.h"

 #define simple_strtoint(c, end, base)	simple_strtol(c, end, base)
 #define simple_strtouint(c, end, base)	simple_strtoul(c, end, base)

 #define STRTO_H(name, type)					\
 int bch_ ## name ## _h(const char *cp, type *res)		\
 {								\
 	int u = 0;						\
 	char *e;						\
 	type i = simple_ ## name(cp, &e, 10);			\
 								\
 	switch (tolower(*e)) {					\
 	default:						\
 		return -EINVAL;					\
 	case 'y':						\
 	case 'z':						\
 		u++;						\
 	case 'e':						\
 		u++;						\
 	case 'p':						\
 		u++;						\
 	case 't':						\
 		u++;						\
 	case 'g':						\
 		u++;						\
 	case 'm':						\
 		u++;						\
 	case 'k':						\
 		u++;						\
 		if (e++ == cp)					\
 			return -EINVAL;				\
 	case '\n':						\
 	case '\0':						\
 		if (*e == '\n')					\
 			e++;					\
 	}							\
 								\
 	if (*e)							\
 		return -EINVAL;					\
 								\
 	while (u--) {						\
 		if ((type) ~0 > 0 &&				\
 		    (type) ~0 / 1024 <= i)			\
 			return -EINVAL;				\
 		if ((i > 0 && ANYSINT_MAX(type) / 1024 < i) ||	\
 		    (i < 0 && -ANYSINT_MAX(type) / 1024 > i))	\
 			return -EINVAL;				\
 		i *= 1024;					\
 	}							\
 								\
 	*res = i;						\
 	return 0;						\
 }								\

 STRTO_H(strtoint, int)
 STRTO_H(strtouint, unsigned int)
 STRTO_H(strtoll, long long)
 STRTO_H(strtoull, unsigned long long)

 /**
  * bch_hprint() - formats @v to human readable string for sysfs.
  *
  * @v - signed 64 bit integer
  * @buf - the (at least 8 byte) buffer to format the result into.
  *
  * Returns the number of bytes used by format.
  */
 ssize_t bch_hprint(char *buf, int64_t v)
 {
 	static const char units[] = "?kMGTPEZY";
 	int u = 0, t;

 	uint64_t q;

 	if (v < 0)
 		q = -v;
 	else
 		q = v;

 	/* For as long as the number is more than 3 digits, but at least
 	 * once, shift right / divide by 1024.  Keep the remainder for
 	 * a digit after the decimal point.
 	 */
 	do {
 		u++;

 		t = q & ~(~0 << 10);
 		q >>= 10;
 	} while (q >= 1000);

 	if (v < 0)
 		/* '-', up to 3 digits, '.', 1 digit, 1 character, null;
 		 * yields 8 bytes.
 		 */
 		return sprintf(buf, "-%llu.%i%c", q, t * 10 / 1024, units[u]);
 	else
 		return sprintf(buf, "%llu.%i%c", q, t * 10 / 1024, units[u]);
 }

 ssize_t bch_snprint_string_list(char *buf, size_t size, const char * const list[],
 			    size_t selected)
 {
 	char *out = buf;
 	size_t i;

 	for (i = 0; list[i]; i++)
 		out += snprintf(out, buf + size - out,
 				i == selected ? "[%s] " : "%s ", list[i]);

 	out[-1] = '\n';
 	return out - buf;
 }

 ssize_t bch_read_string_list(const char *buf, const char * const list[])
 {
 	size_t i;
 	char *s, *d = kstrndup(buf, PAGE_SIZE - 1, GFP_KERNEL);
 	if (!d)
 		return -ENOMEM;

 	s = strim(d);

 	for (i = 0; list[i]; i++)
 		if (!strcmp(list[i], s))
 			break;

 	kfree(d);

 	if (!list[i])
 		return -EINVAL;

 	return i;
 }

 bool bch_is_zero(const char *p, size_t n)
 {
 	size_t i;

 	for (i = 0; i < n; i++)
 		if (p[i])
 			return false;
 	return true;
 }

 int bch_parse_uuid(const char *s, char *uuid)
 {
 	size_t i, j, x;
 	memset(uuid, 0, 16);

 	for (i = 0, j = 0;
 	     i < strspn(s, "-0123456789:ABCDEFabcdef") && j < 32;
 	     i++) {
 		x = s[i] | 32;

 		switch (x) {
 		case '0'...'9':
 			x -= '0';
 			break;
 		case 'a'...'f':
 			x -= 'a' - 10;
 			break;
 		default:
 			continue;
 		}

 		if (!(j & 1))
 			x <<= 4;
 		uuid[j++ >> 1] |= x;
 	}
 	return i;
 }

 void bch_time_stats_update(struct time_stats *stats, uint64_t start_time)
 {
 	uint64_t now, duration, last;

 	spin_lock(&stats->lock);

 	now		= local_clock();
 	duration	= time_after64(now, start_time)
 		? now - start_time : 0;
 	last		= time_after64(now, stats->last)
 		? now - stats->last : 0;

 	stats->max_duration = max(stats->max_duration, duration);

 	if (stats->last) {
 		ewma_add(stats->average_duration, duration, 8, 8);

 		if (stats->average_frequency)
 			ewma_add(stats->average_frequency, last, 8, 8);
 		else
 			stats->average_frequency  = last << 8;
 	} else {
 		stats->average_duration  = duration << 8;
 	}

 	stats->last = now ?: 1;

 	spin_unlock(&stats->lock);
 }

 /**
  * bch_next_delay() - increment @d by the amount of work done, and return how
  * long to delay until the next time to do some work.
  *
  * @d - the struct bch_ratelimit to update
  * @done - the amount of work done, in arbitrary units
  *
  * Returns the amount of time to delay by, in jiffies
  */
 uint64_t bch_next_delay(struct bch_ratelimit *d, uint64_t done)
 {
 	uint64_t now = local_clock();

 	d->next += div_u64(done * NSEC_PER_SEC, d->rate);

 	/* Bound the time.  Don't let us fall further than 2 seconds behind
 	 * (this prevents unnecessary backlog that would make it impossible
 	 * to catch up).  If we're ahead of the desired writeback rate,
 	 * don't let us sleep more than 2.5 seconds (so we can notice/respond
 	 * if the control system tells us to speed up!).
 	 */
 	if (time_before64(now + NSEC_PER_SEC * 5LLU / 2LLU, d->next))
 		d->next = now + NSEC_PER_SEC * 5LLU / 2LLU;

 	if (time_after64(now - NSEC_PER_SEC * 2, d->next))
 		d->next = now - NSEC_PER_SEC * 2;

 	return time_after64(d->next, now)
 		? div_u64(d->next - now, NSEC_PER_SEC / HZ)
 		: 0;
 }

 /*
  * Generally it isn't good to access .bi_io_vec and .bi_vcnt directly,
  * the preferred way is bio_add_page, but in this case, bch_bio_map()
  * supposes that the bvec table is empty, so it is safe to access
  * .bi_vcnt & .bi_io_vec in this way even after multipage bvec is
  * supported.
  */
 void bch_bio_map(struct bio *bio, void *base)
 {
 	size_t size = bio->bi_iter.bi_size;
 	struct bio_vec *bv = bio->bi_io_vec;

 	BUG_ON(!bio->bi_iter.bi_size);
 	BUG_ON(bio->bi_vcnt);

 	bv->bv_offset = base ? offset_in_page(base) : 0;
 	goto start;

 	for (; size; bio->bi_vcnt++, bv++) {
 		bv->bv_offset	= 0;
 start:		bv->bv_len	= min_t(size_t, PAGE_SIZE - bv->bv_offset,
 					size);
 		if (base) {
 			bv->bv_page = is_vmalloc_addr(base)
 				? vmalloc_to_page(base)
 				: virt_to_page(base);

 			base += bv->bv_len;
 		}

 		size -= bv->bv_len;
 	}
 }

 /**
  * bch_bio_alloc_pages - allocates a single page for each bvec in a bio
  * @bio: bio to allocate pages for
  * @gfp_mask: flags for allocation
  *
  * Allocates pages up to @bio->bi_vcnt.
  *
  * Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
  * freed.
  */
 int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
 {
 	int i;
 	struct bio_vec *bv;

 	bio_for_each_segment_all(bv, bio, i) {
 		bv->bv_page = alloc_page(gfp_mask);
 		if (!bv->bv_page) {
 			while (--bv >= bio->bi_io_vec)
 				__free_page(bv->bv_page);
 			return -ENOMEM;
 		}
 	}

 	return 0;
 }

 /*
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group (Any
  * use permitted, subject to terms of PostgreSQL license; see.)

  * If we have a 64-bit integer type, then a 64-bit CRC looks just like the
  * usual sort of implementation. (See Ross Williams' excellent introduction
  * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
  * ftp://ftp.rocksoft.com/papers/crc_v3.txt or several other net sites.)
  * If we have no working 64-bit type, then fake it with two 32-bit registers.
  *
  * The present implementation is a normal (not "reflected", in Williams'
  * terms) 64-bit CRC, using initial all-ones register contents and a final
  * bit inversion. The chosen polynomial is borrowed from the DLT1 spec
  * (ECMA-182, available from http://www.ecma.ch/ecma1/STAND/ECMA-182.HTM):
  *
  * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
  * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
  * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
  * x^7 + x^4 + x + 1
 */

 static const uint64_t crc_table[256] = {
 	0x0000000000000000ULL, 0x42F0E1EBA9EA3693ULL, 0x85E1C3D753D46D26ULL,
 	0xC711223CFA3E5BB5ULL, 0x493366450E42ECDFULL, 0x0BC387AEA7A8DA4CULL,
 	0xCCD2A5925D9681F9ULL, 0x8E224479F47CB76AULL, 0x9266CC8A1C85D9BEULL,
 	0xD0962D61B56FEF2DULL, 0x17870F5D4F51B498ULL, 0x5577EEB6E6BB820BULL,
 	0xDB55AACF12C73561ULL, 0x99A54B24BB2D03F2ULL, 0x5EB4691841135847ULL,
 	0x1C4488F3E8F96ED4ULL, 0x663D78FF90E185EFULL, 0x24CD9914390BB37CULL,
 	0xE3DCBB28C335E8C9ULL, 0xA12C5AC36ADFDE5AULL, 0x2F0E1EBA9EA36930ULL,
 	0x6DFEFF5137495FA3ULL, 0xAAEFDD6DCD770416ULL, 0xE81F3C86649D3285ULL,
 	0xF45BB4758C645C51ULL, 0xB6AB559E258E6AC2ULL, 0x71BA77A2DFB03177ULL,
 	0x334A9649765A07E4ULL, 0xBD68D2308226B08EULL, 0xFF9833DB2BCC861DULL,
 	0x388911E7D1F2DDA8ULL, 0x7A79F00C7818EB3BULL, 0xCC7AF1FF21C30BDEULL,
 	0x8E8A101488293D4DULL, 0x499B3228721766F8ULL, 0x0B6BD3C3DBFD506BULL,
 	0x854997BA2F81E701ULL, 0xC7B97651866BD192ULL, 0x00A8546D7C558A27ULL,
 	0x4258B586D5BFBCB4ULL, 0x5E1C3D753D46D260ULL, 0x1CECDC9E94ACE4F3ULL,
 	0xDBFDFEA26E92BF46ULL, 0x990D1F49C77889D5ULL, 0x172F5B3033043EBFULL,
 	0x55DFBADB9AEE082CULL, 0x92CE98E760D05399ULL, 0xD03E790CC93A650AULL,
 	0xAA478900B1228E31ULL, 0xE8B768EB18C8B8A2ULL, 0x2FA64AD7E2F6E317ULL,
 	0x6D56AB3C4B1CD584ULL, 0xE374EF45BF6062EEULL, 0xA1840EAE168A547DULL,
 	0x66952C92ECB40FC8ULL, 0x2465CD79455E395BULL, 0x3821458AADA7578FULL,
 	0x7AD1A461044D611CULL, 0xBDC0865DFE733AA9ULL, 0xFF3067B657990C3AULL,
 	0x711223CFA3E5BB50ULL, 0x33E2C2240A0F8DC3ULL, 0xF4F3E018F031D676ULL,
 	0xB60301F359DBE0E5ULL, 0xDA050215EA6C212FULL, 0x98F5E3FE438617BCULL,
 	0x5FE4C1C2B9B84C09ULL, 0x1D14202910527A9AULL, 0x93366450E42ECDF0ULL,
 	0xD1C685BB4DC4FB63ULL, 0x16D7A787B7FAA0D6ULL, 0x5427466C1E109645ULL,
 	0x4863CE9FF6E9F891ULL, 0x0A932F745F03CE02ULL, 0xCD820D48A53D95B7ULL,
 	0x8F72ECA30CD7A324ULL, 0x0150A8DAF8AB144EULL, 0x43A04931514122DDULL,
 	0x84B16B0DAB7F7968ULL, 0xC6418AE602954FFBULL, 0xBC387AEA7A8DA4C0ULL,
 	0xFEC89B01D3679253ULL, 0x39D9B93D2959C9E6ULL, 0x7B2958D680B3FF75ULL,
 	0xF50B1CAF74CF481FULL, 0xB7FBFD44DD257E8CULL, 0x70EADF78271B2539ULL,
 	0x321A3E938EF113AAULL, 0x2E5EB66066087D7EULL, 0x6CAE578BCFE24BEDULL,
 	0xABBF75B735DC1058ULL, 0xE94F945C9C3626CBULL, 0x676DD025684A91A1ULL,
 	0x259D31CEC1A0A732ULL, 0xE28C13F23B9EFC87ULL, 0xA07CF2199274CA14ULL,
 	0x167FF3EACBAF2AF1ULL, 0x548F120162451C62ULL, 0x939E303D987B47D7ULL,
 	0xD16ED1D631917144ULL, 0x5F4C95AFC5EDC62EULL, 0x1DBC74446C07F0BDULL,
 	0xDAAD56789639AB08ULL, 0x985DB7933FD39D9BULL, 0x84193F60D72AF34FULL,
 	0xC6E9DE8B7EC0C5DCULL, 0x01F8FCB784FE9E69ULL, 0x43081D5C2D14A8FAULL,
 	0xCD2A5925D9681F90ULL, 0x8FDAB8CE70822903ULL, 0x48CB9AF28ABC72B6ULL,
 	0x0A3B7B1923564425ULL, 0x70428B155B4EAF1EULL, 0x32B26AFEF2A4998DULL,
 	0xF5A348C2089AC238ULL, 0xB753A929A170F4ABULL, 0x3971ED50550C43C1ULL,
 	0x7B810CBBFCE67552ULL, 0xBC902E8706D82EE7ULL, 0xFE60CF6CAF321874ULL,
 	0xE224479F47CB76A0ULL, 0xA0D4A674EE214033ULL, 0x67C58448141F1B86ULL,
 	0x253565A3BDF52D15ULL, 0xAB1721DA49899A7FULL, 0xE9E7C031E063ACECULL,
 	0x2EF6E20D1A5DF759ULL, 0x6C0603E6B3B7C1CAULL, 0xF6FAE5C07D3274CDULL,
 	0xB40A042BD4D8425EULL, 0x731B26172EE619EBULL, 0x31EBC7FC870C2F78ULL,
 	0xBFC9838573709812ULL, 0xFD39626EDA9AAE81ULL, 0x3A28405220A4F534ULL,
 	0x78D8A1B9894EC3A7ULL, 0x649C294A61B7AD73ULL, 0x266CC8A1C85D9BE0ULL,
 	0xE17DEA9D3263C055ULL, 0xA38D0B769B89F6C6ULL, 0x2DAF4F0F6FF541ACULL,
 	0x6F5FAEE4C61F773FULL, 0xA84E8CD83C212C8AULL, 0xEABE6D3395CB1A19ULL,
 	0x90C79D3FEDD3F122ULL, 0xD2377CD44439C7B1ULL, 0x15265EE8BE079C04ULL,
 	0x57D6BF0317EDAA97ULL, 0xD9F4FB7AE3911DFDULL, 0x9B041A914A7B2B6EULL,
 	0x5C1538ADB04570DBULL, 0x1EE5D94619AF4648ULL, 0x02A151B5F156289CULL,
 	0x4051B05E58BC1E0FULL, 0x87409262A28245BAULL, 0xC5B073890B687329ULL,
 	0x4B9237F0FF14C443ULL, 0x0962D61B56FEF2D0ULL, 0xCE73F427ACC0A965ULL,
 	0x8C8315CC052A9FF6ULL, 0x3A80143F5CF17F13ULL, 0x7870F5D4F51B4980ULL,
 	0xBF61D7E80F251235ULL, 0xFD913603A6CF24A6ULL, 0x73B3727A52B393CCULL,
 	0x31439391FB59A55FULL, 0xF652B1AD0167FEEAULL, 0xB4A25046A88DC879ULL,
 	0xA8E6D8B54074A6ADULL, 0xEA16395EE99E903EULL, 0x2D071B6213A0CB8BULL,
 	0x6FF7FA89BA4AFD18ULL, 0xE1D5BEF04E364A72ULL, 0xA3255F1BE7DC7CE1ULL,
 	0x64347D271DE22754ULL, 0x26C49CCCB40811C7ULL, 0x5CBD6CC0CC10FAFCULL,
 	0x1E4D8D2B65FACC6FULL, 0xD95CAF179FC497DAULL, 0x9BAC4EFC362EA149ULL,
 	0x158E0A85C2521623ULL, 0x577EEB6E6BB820B0ULL, 0x906FC95291867B05ULL,
 	0xD29F28B9386C4D96ULL, 0xCEDBA04AD0952342ULL, 0x8C2B41A1797F15D1ULL,
 	0x4B3A639D83414E64ULL, 0x09CA82762AAB78F7ULL, 0x87E8C60FDED7CF9DULL,
 	0xC51827E4773DF90EULL, 0x020905D88D03A2BBULL, 0x40F9E43324E99428ULL,
 	0x2CFFE7D5975E55E2ULL, 0x6E0F063E3EB46371ULL, 0xA91E2402C48A38C4ULL,
 	0xEBEEC5E96D600E57ULL, 0x65CC8190991CB93DULL, 0x273C607B30F68FAEULL,
 	0xE02D4247CAC8D41BULL, 0xA2DDA3AC6322E288ULL, 0xBE992B5F8BDB8C5CULL,
 	0xFC69CAB42231BACFULL, 0x3B78E888D80FE17AULL, 0x7988096371E5D7E9ULL,
 	0xF7AA4D1A85996083ULL, 0xB55AACF12C735610ULL, 0x724B8ECDD64D0DA5ULL,
 	0x30BB6F267FA73B36ULL, 0x4AC29F2A07BFD00DULL, 0x08327EC1AE55E69EULL,
 	0xCF235CFD546BBD2BULL, 0x8DD3BD16FD818BB8ULL, 0x03F1F96F09FD3CD2ULL,
 	0x41011884A0170A41ULL, 0x86103AB85A2951F4ULL, 0xC4E0DB53F3C36767ULL,
 	0xD8A453A01B3A09B3ULL, 0x9A54B24BB2D03F20ULL, 0x5D45907748EE6495ULL,
 	0x1FB5719CE1045206ULL, 0x919735E51578E56CULL, 0xD367D40EBC92D3FFULL,
 	0x1476F63246AC884AULL, 0x568617D9EF46BED9ULL, 0xE085162AB69D5E3CULL,
 	0xA275F7C11F7768AFULL, 0x6564D5FDE549331AULL, 0x279434164CA30589ULL,
 	0xA9B6706FB8DFB2E3ULL, 0xEB46918411358470ULL, 0x2C57B3B8EB0BDFC5ULL,
 	0x6EA7525342E1E956ULL, 0x72E3DAA0AA188782ULL, 0x30133B4B03F2B111ULL,
 	0xF7021977F9CCEAA4ULL, 0xB5F2F89C5026DC37ULL, 0x3BD0BCE5A45A6B5DULL,
 	0x79205D0E0DB05DCEULL, 0xBE317F32F78E067BULL, 0xFCC19ED95E6430E8ULL,
 	0x86B86ED5267CDBD3ULL, 0xC4488F3E8F96ED40ULL, 0x0359AD0275A8B6F5ULL,
 	0x41A94CE9DC428066ULL, 0xCF8B0890283E370CULL, 0x8D7BE97B81D4019FULL,
 	0x4A6ACB477BEA5A2AULL, 0x089A2AACD2006CB9ULL, 0x14DEA25F3AF9026DULL,
 	0x562E43B4931334FEULL, 0x913F6188692D6F4BULL, 0xD3CF8063C0C759D8ULL,
 	0x5DEDC41A34BBEEB2ULL, 0x1F1D25F19D51D821ULL, 0xD80C07CD676F8394ULL,
 	0x9AFCE626CE85B507ULL,
 };

 uint64_t bch_crc64_update(uint64_t crc, const void *_data, size_t len)
 {
 	const unsigned char *data = _data;

 	while (len--) {
 		int i = ((int) (crc >> 56) ^ *data++) & 0xFF;
 		crc = crc_table[i] ^ (crc << 8);
 	}

 	return crc;
 }

 uint64_t bch_crc64(const void *data, size_t len)
 {
 	uint64_t crc = 0xffffffffffffffffULL;

 	crc = bch_crc64_update(crc, data, len);

 	return crc ^ 0xffffffffffffffffULL;
 }
	/*
	* random utiility code, for bcache but in theory not specific to bcache
	*
	* Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
	* Copyright 2012 Google, Inc.
	*/

	#include <linux/bio.h>
	#include <linux/blkdev.h>
	#include <linux/ctype.h>
	#include <linux/debugfs.h>
	#include <linux/module.h>
	#include <linux/seq_file.h>
	#include <linux/types.h>
	#include <linux/sched/clock.h>

	#include "util.h"

	#define simple_strtoint(c, end, base) simple_strtol(c, end, base)
	#define simple_strtouint(c, end, base) simple_strtoul(c, end, base)

	#define STRTO_H(name, type) \
	int bch_ ## name ## _h(const char cp, type res) \
	{ \
	int u = 0; \
	char *e; \
	type i = simple_ ## name(cp, &e, 10); \
	\
	switch (tolower(*e)) { \
	default: \
	return -EINVAL; \
	case 'y': \
	case 'z': \
	u++; \
	case 'e': \
	u++; \
	case 'p': \
	u++; \
	case 't': \
	u++; \
	case 'g': \
	u++; \
	case 'm': \
	u++; \
	case 'k': \
	u++; \
	if (e++ == cp) \
	return -EINVAL; \
	case '\n': \
	case '\0': \
	if (*e == '\n') \
	e++; \
	} \
	\
	if (*e) \
	return -EINVAL; \
	\
	while (u--) { \
	if ((type) ~0 > 0 && \
	(type) ~0 / 1024 <= i) \
	return -EINVAL; \
	if ((i > 0 && ANYSINT_MAX(type) / 1024 < i) \|\| \
	(i < 0 && -ANYSINT_MAX(type) / 1024 > i)) \
	return -EINVAL; \
	i *= 1024; \
	} \
	\
	*res = i; \
	return 0; \
	} \

	STRTO_H(strtoint, int)
	STRTO_H(strtouint, unsigned int)
	STRTO_H(strtoll, long long)
	STRTO_H(strtoull, unsigned long long)

	/**
	* bch_hprint() - formats @v to human readable string for sysfs.
	*
	* @v - signed 64 bit integer
	* @buf - the (at least 8 byte) buffer to format the result into.
	*
	* Returns the number of bytes used by format.
	*/
	ssize_t bch_hprint(char *buf, int64_t v)
	{
	static const char units[] = "?kMGTPEZY";
	int u = 0, t;

	uint64_t q;

	if (v < 0)
	q = -v;
	else
	q = v;

	/* For as long as the number is more than 3 digits, but at least
	* once, shift right / divide by 1024. Keep the remainder for
	* a digit after the decimal point.
	*/
	do {
	u++;

	t = q & ~(~0 << 10);
	q >>= 10;
	} while (q >= 1000);

	if (v < 0)
	/* '-', up to 3 digits, '.', 1 digit, 1 character, null;
	* yields 8 bytes.
	*/
	return sprintf(buf, "-%llu.%i%c", q, t * 10 / 1024, units[u]);
	else
	return sprintf(buf, "%llu.%i%c", q, t * 10 / 1024, units[u]);
	}

	ssize_t bch_snprint_string_list(char buf, size_t size, const char const list[],
	size_t selected)
	{
	char *out = buf;
	size_t i;

	for (i = 0; list[i]; i++)
	out += snprintf(out, buf + size - out,
	i == selected ? "[%s] " : "%s ", list[i]);

	out[-1] = '\n';
	return out - buf;
	}

	ssize_t bch_read_string_list(const char buf, const char const list[])
	{
	size_t i;
	char s, d = kstrndup(buf, PAGE_SIZE - 1, GFP_KERNEL);
	if (!d)
	return -ENOMEM;

	s = strim(d);

	for (i = 0; list[i]; i++)
	if (!strcmp(list[i], s))
	break;

	kfree(d);

	if (!list[i])
	return -EINVAL;

	return i;
	}

	bool bch_is_zero(const char *p, size_t n)
	{
	size_t i;

	for (i = 0; i < n; i++)
	if (p[i])
	return false;
	return true;
	}

	int bch_parse_uuid(const char s, char uuid)
	{
	size_t i, j, x;
	memset(uuid, 0, 16);

	for (i = 0, j = 0;
	i < strspn(s, "-0123456789:ABCDEFabcdef") && j < 32;
	i++) {
	x = s[i] \| 32;

	switch (x) {
	case '0'...'9':
	x -= '0';
	break;
	case 'a'...'f':
	x -= 'a' - 10;
	break;
	default:
	continue;
	}

	if (!(j & 1))
	x <<= 4;
	uuid[j++ >> 1] \|= x;
	}
	return i;
	}

	void bch_time_stats_update(struct time_stats *stats, uint64_t start_time)
	{
	uint64_t now, duration, last;

	spin_lock(&stats->lock);

	now = local_clock();
	duration = time_after64(now, start_time)
	? now - start_time : 0;
	last = time_after64(now, stats->last)
	? now - stats->last : 0;

	stats->max_duration = max(stats->max_duration, duration);

	if (stats->last) {
	ewma_add(stats->average_duration, duration, 8, 8);

	if (stats->average_frequency)
	ewma_add(stats->average_frequency, last, 8, 8);
	else
	stats->average_frequency = last << 8;
	} else {
	stats->average_duration = duration << 8;
	}

	stats->last = now ?: 1;

	spin_unlock(&stats->lock);
	}

	/**
	* bch_next_delay() - increment @d by the amount of work done, and return how
	* long to delay until the next time to do some work.
	*
	* @d - the struct bch_ratelimit to update
	* @done - the amount of work done, in arbitrary units
	*
	* Returns the amount of time to delay by, in jiffies
	*/
	uint64_t bch_next_delay(struct bch_ratelimit *d, uint64_t done)
	{
	uint64_t now = local_clock();

	d->next += div_u64(done * NSEC_PER_SEC, d->rate);

	/* Bound the time. Don't let us fall further than 2 seconds behind
	* (this prevents unnecessary backlog that would make it impossible
	* to catch up). If we're ahead of the desired writeback rate,
	* don't let us sleep more than 2.5 seconds (so we can notice/respond
	* if the control system tells us to speed up!).
	*/
	if (time_before64(now + NSEC_PER_SEC * 5LLU / 2LLU, d->next))
	d->next = now + NSEC_PER_SEC * 5LLU / 2LLU;

	if (time_after64(now - NSEC_PER_SEC * 2, d->next))
	d->next = now - NSEC_PER_SEC * 2;

	return time_after64(d->next, now)
	? div_u64(d->next - now, NSEC_PER_SEC / HZ)
	: 0;
	}

	/*
	* Generally it isn't good to access .bi_io_vec and .bi_vcnt directly,
	* the preferred way is bio_add_page, but in this case, bch_bio_map()
	* supposes that the bvec table is empty, so it is safe to access
	* .bi_vcnt & .bi_io_vec in this way even after multipage bvec is
	* supported.
	*/
	void bch_bio_map(struct bio bio, void base)
	{
	size_t size = bio->bi_iter.bi_size;
	struct bio_vec *bv = bio->bi_io_vec;

	BUG_ON(!bio->bi_iter.bi_size);
	BUG_ON(bio->bi_vcnt);

	bv->bv_offset = base ? offset_in_page(base) : 0;
	goto start;

	for (; size; bio->bi_vcnt++, bv++) {
	bv->bv_offset = 0;
	start: bv->bv_len = min_t(size_t, PAGE_SIZE - bv->bv_offset,
	size);
	if (base) {
	bv->bv_page = is_vmalloc_addr(base)
	? vmalloc_to_page(base)
	: virt_to_page(base);

	base += bv->bv_len;
	}

	size -= bv->bv_len;
	}
	}

	/**
	* bch_bio_alloc_pages - allocates a single page for each bvec in a bio
	* @bio: bio to allocate pages for
	* @gfp_mask: flags for allocation
	*
	* Allocates pages up to @bio->bi_vcnt.
	*
	* Returns 0 on success, -ENOMEM on failure. On failure, any allocated pages are
	* freed.
	*/
	int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
	{
	int i;
	struct bio_vec *bv;

	bio_for_each_segment_all(bv, bio, i) {
	bv->bv_page = alloc_page(gfp_mask);
	if (!bv->bv_page) {
	while (--bv >= bio->bi_io_vec)
	__free_page(bv->bv_page);
	return -ENOMEM;
	}
	}

	return 0;
	}

	/*
	* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group (Any
	* use permitted, subject to terms of PostgreSQL license; see.)

	* If we have a 64-bit integer type, then a 64-bit CRC looks just like the
	* usual sort of implementation. (See Ross Williams' excellent introduction
	* A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
	* ftp://ftp.rocksoft.com/papers/crc_v3.txt or several other net sites.)
	* If we have no working 64-bit type, then fake it with two 32-bit registers.
	*
	* The present implementation is a normal (not "reflected", in Williams'
	* terms) 64-bit CRC, using initial all-ones register contents and a final
	* bit inversion. The chosen polynomial is borrowed from the DLT1 spec
	* (ECMA-182, available from http://www.ecma.ch/ecma1/STAND/ECMA-182.HTM):
	*
	* x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
	* x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
	* x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
	* x^7 + x^4 + x + 1
	*/

	static const uint64_t crc_table[256] = {
	0x0000000000000000ULL, 0x42F0E1EBA9EA3693ULL, 0x85E1C3D753D46D26ULL,
	0xC711223CFA3E5BB5ULL, 0x493366450E42ECDFULL, 0x0BC387AEA7A8DA4CULL,
	0xCCD2A5925D9681F9ULL, 0x8E224479F47CB76AULL, 0x9266CC8A1C85D9BEULL,
	0xD0962D61B56FEF2DULL, 0x17870F5D4F51B498ULL, 0x5577EEB6E6BB820BULL,
	0xDB55AACF12C73561ULL, 0x99A54B24BB2D03F2ULL, 0x5EB4691841135847ULL,
	0x1C4488F3E8F96ED4ULL, 0x663D78FF90E185EFULL, 0x24CD9914390BB37CULL,
	0xE3DCBB28C335E8C9ULL, 0xA12C5AC36ADFDE5AULL, 0x2F0E1EBA9EA36930ULL,
	0x6DFEFF5137495FA3ULL, 0xAAEFDD6DCD770416ULL, 0xE81F3C86649D3285ULL,
	0xF45BB4758C645C51ULL, 0xB6AB559E258E6AC2ULL, 0x71BA77A2DFB03177ULL,
	0x334A9649765A07E4ULL, 0xBD68D2308226B08EULL, 0xFF9833DB2BCC861DULL,
	0x388911E7D1F2DDA8ULL, 0x7A79F00C7818EB3BULL, 0xCC7AF1FF21C30BDEULL,
	0x8E8A101488293D4DULL, 0x499B3228721766F8ULL, 0x0B6BD3C3DBFD506BULL,
	0x854997BA2F81E701ULL, 0xC7B97651866BD192ULL, 0x00A8546D7C558A27ULL,
	0x4258B586D5BFBCB4ULL, 0x5E1C3D753D46D260ULL, 0x1CECDC9E94ACE4F3ULL,
	0xDBFDFEA26E92BF46ULL, 0x990D1F49C77889D5ULL, 0x172F5B3033043EBFULL,
	0x55DFBADB9AEE082CULL, 0x92CE98E760D05399ULL, 0xD03E790CC93A650AULL,
	0xAA478900B1228E31ULL, 0xE8B768EB18C8B8A2ULL, 0x2FA64AD7E2F6E317ULL,
	0x6D56AB3C4B1CD584ULL, 0xE374EF45BF6062EEULL, 0xA1840EAE168A547DULL,
	0x66952C92ECB40FC8ULL, 0x2465CD79455E395BULL, 0x3821458AADA7578FULL,
	0x7AD1A461044D611CULL, 0xBDC0865DFE733AA9ULL, 0xFF3067B657990C3AULL,
	0x711223CFA3E5BB50ULL, 0x33E2C2240A0F8DC3ULL, 0xF4F3E018F031D676ULL,
	0xB60301F359DBE0E5ULL, 0xDA050215EA6C212FULL, 0x98F5E3FE438617BCULL,
	0x5FE4C1C2B9B84C09ULL, 0x1D14202910527A9AULL, 0x93366450E42ECDF0ULL,
	0xD1C685BB4DC4FB63ULL, 0x16D7A787B7FAA0D6ULL, 0x5427466C1E109645ULL,
	0x4863CE9FF6E9F891ULL, 0x0A932F745F03CE02ULL, 0xCD820D48A53D95B7ULL,
	0x8F72ECA30CD7A324ULL, 0x0150A8DAF8AB144EULL, 0x43A04931514122DDULL,
	0x84B16B0DAB7F7968ULL, 0xC6418AE602954FFBULL, 0xBC387AEA7A8DA4C0ULL,
	0xFEC89B01D3679253ULL, 0x39D9B93D2959C9E6ULL, 0x7B2958D680B3FF75ULL,
	0xF50B1CAF74CF481FULL, 0xB7FBFD44DD257E8CULL, 0x70EADF78271B2539ULL,
	0x321A3E938EF113AAULL, 0x2E5EB66066087D7EULL, 0x6CAE578BCFE24BEDULL,
	0xABBF75B735DC1058ULL, 0xE94F945C9C3626CBULL, 0x676DD025684A91A1ULL,
	0x259D31CEC1A0A732ULL, 0xE28C13F23B9EFC87ULL, 0xA07CF2199274CA14ULL,
	0x167FF3EACBAF2AF1ULL, 0x548F120162451C62ULL, 0x939E303D987B47D7ULL,
	0xD16ED1D631917144ULL, 0x5F4C95AFC5EDC62EULL, 0x1DBC74446C07F0BDULL,
	0xDAAD56789639AB08ULL, 0x985DB7933FD39D9BULL, 0x84193F60D72AF34FULL,
	0xC6E9DE8B7EC0C5DCULL, 0x01F8FCB784FE9E69ULL, 0x43081D5C2D14A8FAULL,
	0xCD2A5925D9681F90ULL, 0x8FDAB8CE70822903ULL, 0x48CB9AF28ABC72B6ULL,
	0x0A3B7B1923564425ULL, 0x70428B155B4EAF1EULL, 0x32B26AFEF2A4998DULL,
	0xF5A348C2089AC238ULL, 0xB753A929A170F4ABULL, 0x3971ED50550C43C1ULL,
	0x7B810CBBFCE67552ULL, 0xBC902E8706D82EE7ULL, 0xFE60CF6CAF321874ULL,
	0xE224479F47CB76A0ULL, 0xA0D4A674EE214033ULL, 0x67C58448141F1B86ULL,
	0x253565A3BDF52D15ULL, 0xAB1721DA49899A7FULL, 0xE9E7C031E063ACECULL,
	0x2EF6E20D1A5DF759ULL, 0x6C0603E6B3B7C1CAULL, 0xF6FAE5C07D3274CDULL,
	0xB40A042BD4D8425EULL, 0x731B26172EE619EBULL, 0x31EBC7FC870C2F78ULL,
	0xBFC9838573709812ULL, 0xFD39626EDA9AAE81ULL, 0x3A28405220A4F534ULL,
	0x78D8A1B9894EC3A7ULL, 0x649C294A61B7AD73ULL, 0x266CC8A1C85D9BE0ULL,
	0xE17DEA9D3263C055ULL, 0xA38D0B769B89F6C6ULL, 0x2DAF4F0F6FF541ACULL,
	0x6F5FAEE4C61F773FULL, 0xA84E8CD83C212C8AULL, 0xEABE6D3395CB1A19ULL,
	0x90C79D3FEDD3F122ULL, 0xD2377CD44439C7B1ULL, 0x15265EE8BE079C04ULL,
	0x57D6BF0317EDAA97ULL, 0xD9F4FB7AE3911DFDULL, 0x9B041A914A7B2B6EULL,
	0x5C1538ADB04570DBULL, 0x1EE5D94619AF4648ULL, 0x02A151B5F156289CULL,
	0x4051B05E58BC1E0FULL, 0x87409262A28245BAULL, 0xC5B073890B687329ULL,
	0x4B9237F0FF14C443ULL, 0x0962D61B56FEF2D0ULL, 0xCE73F427ACC0A965ULL,
	0x8C8315CC052A9FF6ULL, 0x3A80143F5CF17F13ULL, 0x7870F5D4F51B4980ULL,
	0xBF61D7E80F251235ULL, 0xFD913603A6CF24A6ULL, 0x73B3727A52B393CCULL,
	0x31439391FB59A55FULL, 0xF652B1AD0167FEEAULL, 0xB4A25046A88DC879ULL,
	0xA8E6D8B54074A6ADULL, 0xEA16395EE99E903EULL, 0x2D071B6213A0CB8BULL,
	0x6FF7FA89BA4AFD18ULL, 0xE1D5BEF04E364A72ULL, 0xA3255F1BE7DC7CE1ULL,
	0x64347D271DE22754ULL, 0x26C49CCCB40811C7ULL, 0x5CBD6CC0CC10FAFCULL,
	0x1E4D8D2B65FACC6FULL, 0xD95CAF179FC497DAULL, 0x9BAC4EFC362EA149ULL,
	0x158E0A85C2521623ULL, 0x577EEB6E6BB820B0ULL, 0x906FC95291867B05ULL,
	0xD29F28B9386C4D96ULL, 0xCEDBA04AD0952342ULL, 0x8C2B41A1797F15D1ULL,
	0x4B3A639D83414E64ULL, 0x09CA82762AAB78F7ULL, 0x87E8C60FDED7CF9DULL,
	0xC51827E4773DF90EULL, 0x020905D88D03A2BBULL, 0x40F9E43324E99428ULL,
	0x2CFFE7D5975E55E2ULL, 0x6E0F063E3EB46371ULL, 0xA91E2402C48A38C4ULL,
	0xEBEEC5E96D600E57ULL, 0x65CC8190991CB93DULL, 0x273C607B30F68FAEULL,
	0xE02D4247CAC8D41BULL, 0xA2DDA3AC6322E288ULL, 0xBE992B5F8BDB8C5CULL,
	0xFC69CAB42231BACFULL, 0x3B78E888D80FE17AULL, 0x7988096371E5D7E9ULL,
	0xF7AA4D1A85996083ULL, 0xB55AACF12C735610ULL, 0x724B8ECDD64D0DA5ULL,
	0x30BB6F267FA73B36ULL, 0x4AC29F2A07BFD00DULL, 0x08327EC1AE55E69EULL,
	0xCF235CFD546BBD2BULL, 0x8DD3BD16FD818BB8ULL, 0x03F1F96F09FD3CD2ULL,
	0x41011884A0170A41ULL, 0x86103AB85A2951F4ULL, 0xC4E0DB53F3C36767ULL,
	0xD8A453A01B3A09B3ULL, 0x9A54B24BB2D03F20ULL, 0x5D45907748EE6495ULL,
	0x1FB5719CE1045206ULL, 0x919735E51578E56CULL, 0xD367D40EBC92D3FFULL,
	0x1476F63246AC884AULL, 0x568617D9EF46BED9ULL, 0xE085162AB69D5E3CULL,
	0xA275F7C11F7768AFULL, 0x6564D5FDE549331AULL, 0x279434164CA30589ULL,
	0xA9B6706FB8DFB2E3ULL, 0xEB46918411358470ULL, 0x2C57B3B8EB0BDFC5ULL,
	0x6EA7525342E1E956ULL, 0x72E3DAA0AA188782ULL, 0x30133B4B03F2B111ULL,
	0xF7021977F9CCEAA4ULL, 0xB5F2F89C5026DC37ULL, 0x3BD0BCE5A45A6B5DULL,
	0x79205D0E0DB05DCEULL, 0xBE317F32F78E067BULL, 0xFCC19ED95E6430E8ULL,
	0x86B86ED5267CDBD3ULL, 0xC4488F3E8F96ED40ULL, 0x0359AD0275A8B6F5ULL,
	0x41A94CE9DC428066ULL, 0xCF8B0890283E370CULL, 0x8D7BE97B81D4019FULL,
	0x4A6ACB477BEA5A2AULL, 0x089A2AACD2006CB9ULL, 0x14DEA25F3AF9026DULL,
	0x562E43B4931334FEULL, 0x913F6188692D6F4BULL, 0xD3CF8063C0C759D8ULL,
	0x5DEDC41A34BBEEB2ULL, 0x1F1D25F19D51D821ULL, 0xD80C07CD676F8394ULL,
	0x9AFCE626CE85B507ULL,
	};

	uint64_t bch_crc64_update(uint64_t crc, const void *_data, size_t len)
	{
	const unsigned char *data = _data;

	while (len--) {
	int i = ((int) (crc >> 56) ^ *data++) & 0xFF;
	crc = crc_table[i] ^ (crc << 8);
	}

	return crc;
	}

	uint64_t bch_crc64(const void *data, size_t len)
	{
	uint64_t crc = 0xffffffffffffffffULL;

	crc = bch_crc64_update(crc, data, len);

	return crc ^ 0xffffffffffffffffULL;
	}