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1// SPDX-License-Identifier: GPL-2.02/*3 * SE/HMC Drive (Read) Cache Functions4 *5 * Copyright IBM Corp. 20136 * Author(s): Ralf Hoppe (rhoppe@de.ibm.com)7 *8 */9 10#define KMSG_COMPONENT "hmcdrv"11#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt12 13#include <linux/kernel.h>14#include <linux/mm.h>15#include <linux/jiffies.h>16 17#include "hmcdrv_ftp.h"18#include "hmcdrv_cache.h"19 20#define HMCDRV_CACHE_TIMEOUT 30 /* aging timeout in seconds */21 22/**23 * struct hmcdrv_cache_entry - file cache (only used on read/dir)24 * @id: FTP command ID25 * @content: kernel-space buffer, 4k aligned26 * @len: size of @content cache (0 if caching disabled)27 * @ofs: start of content within file (-1 if no cached content)28 * @fname: file name29 * @fsize: file size30 * @timeout: cache timeout in jiffies31 *32 * Notice that the first three members (id, fname, fsize) are cached on all33 * read/dir requests. But content is cached only under some preconditions.34 * Uncached content is signalled by a negative value of @ofs.35 */36struct hmcdrv_cache_entry {37 enum hmcdrv_ftp_cmdid id;38 char fname[HMCDRV_FTP_FIDENT_MAX];39 size_t fsize;40 loff_t ofs;41 unsigned long timeout;42 void *content;43 size_t len;44};45 46static int hmcdrv_cache_order; /* cache allocated page order */47 48static struct hmcdrv_cache_entry hmcdrv_cache_file = {49 .fsize = SIZE_MAX,50 .ofs = -1,51 .len = 0,52 .fname = {'\0'}53};54 55/**56 * hmcdrv_cache_get() - looks for file data/content in read cache57 * @ftp: pointer to FTP command specification58 *59 * Return: number of bytes read from cache or a negative number if nothing60 * in content cache (for the file/cmd specified in @ftp)61 */62static ssize_t hmcdrv_cache_get(const struct hmcdrv_ftp_cmdspec *ftp)63{64 loff_t pos; /* position in cache (signed) */65 ssize_t len;66 67 if ((ftp->id != hmcdrv_cache_file.id) ||68 strcmp(hmcdrv_cache_file.fname, ftp->fname))69 return -1;70 71 if (ftp->ofs >= hmcdrv_cache_file.fsize) /* EOF ? */72 return 0;73 74 if ((hmcdrv_cache_file.ofs < 0) || /* has content? */75 time_after(jiffies, hmcdrv_cache_file.timeout))76 return -1;77 78 /* there seems to be cached content - calculate the maximum number79 * of bytes that can be returned (regarding file size and offset)80 */81 len = hmcdrv_cache_file.fsize - ftp->ofs;82 83 if (len > ftp->len)84 len = ftp->len;85 86 /* check if the requested chunk falls into our cache (which starts87 * at offset 'hmcdrv_cache_file.ofs' in the file of interest)88 */89 pos = ftp->ofs - hmcdrv_cache_file.ofs;90 91 if ((pos >= 0) &&92 ((pos + len) <= hmcdrv_cache_file.len)) {93 94 memcpy(ftp->buf,95 hmcdrv_cache_file.content + pos,96 len);97 pr_debug("using cached content of '%s', returning %zd/%zd bytes\n",98 hmcdrv_cache_file.fname, len,99 hmcdrv_cache_file.fsize);100 101 return len;102 }103 104 return -1;105}106 107/**108 * hmcdrv_cache_do() - do a HMC drive CD/DVD transfer with cache update109 * @ftp: pointer to FTP command specification110 * @func: FTP transfer function to be used111 *112 * Return: number of bytes read/written or a (negative) error code113 */114static ssize_t hmcdrv_cache_do(const struct hmcdrv_ftp_cmdspec *ftp,115 hmcdrv_cache_ftpfunc func)116{117 ssize_t len;118 119 /* only cache content if the read/dir cache really exists120 * (hmcdrv_cache_file.len > 0), is large enough to handle the121 * request (hmcdrv_cache_file.len >= ftp->len) and there is a need122 * to do so (ftp->len > 0)123 */124 if ((ftp->len > 0) && (hmcdrv_cache_file.len >= ftp->len)) {125 126 /* because the cache is not located at ftp->buf, we have to127 * assemble a new HMC drive FTP cmd specification (pointing128 * to our cache, and using the increased size)129 */130 struct hmcdrv_ftp_cmdspec cftp = *ftp; /* make a copy */131 cftp.buf = hmcdrv_cache_file.content; /* and update */132 cftp.len = hmcdrv_cache_file.len; /* buffer data */133 134 len = func(&cftp, &hmcdrv_cache_file.fsize); /* now do */135 136 if (len > 0) {137 pr_debug("caching %zd bytes content for '%s'\n",138 len, ftp->fname);139 140 if (len > ftp->len)141 len = ftp->len;142 143 hmcdrv_cache_file.ofs = ftp->ofs;144 hmcdrv_cache_file.timeout = jiffies +145 HMCDRV_CACHE_TIMEOUT * HZ;146 memcpy(ftp->buf, hmcdrv_cache_file.content, len);147 }148 } else {149 len = func(ftp, &hmcdrv_cache_file.fsize);150 hmcdrv_cache_file.ofs = -1; /* invalidate content */151 }152 153 if (len > 0) {154 /* cache some file info (FTP command, file name and file155 * size) unconditionally156 */157 strscpy(hmcdrv_cache_file.fname, ftp->fname,158 HMCDRV_FTP_FIDENT_MAX);159 hmcdrv_cache_file.id = ftp->id;160 pr_debug("caching cmd %d, file size %zu for '%s'\n",161 ftp->id, hmcdrv_cache_file.fsize, ftp->fname);162 }163 164 return len;165}166 167/**168 * hmcdrv_cache_cmd() - perform a cached HMC drive CD/DVD transfer169 * @ftp: pointer to FTP command specification170 * @func: FTP transfer function to be used171 *172 * Attention: Notice that this function is not reentrant - so the caller173 * must ensure exclusive execution.174 *175 * Return: number of bytes read/written or a (negative) error code176 */177ssize_t hmcdrv_cache_cmd(const struct hmcdrv_ftp_cmdspec *ftp,178 hmcdrv_cache_ftpfunc func)179{180 ssize_t len;181 182 if ((ftp->id == HMCDRV_FTP_DIR) || /* read cache */183 (ftp->id == HMCDRV_FTP_NLIST) ||184 (ftp->id == HMCDRV_FTP_GET)) {185 186 len = hmcdrv_cache_get(ftp);187 188 if (len >= 0) /* got it from cache ? */189 return len; /* yes */190 191 len = hmcdrv_cache_do(ftp, func);192 193 if (len >= 0)194 return len;195 196 } else {197 len = func(ftp, NULL); /* simply do original command */198 }199 200 /* invalidate the (read) cache in case there was a write operation201 * or an error on read/dir202 */203 hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;204 hmcdrv_cache_file.fsize = LLONG_MAX;205 hmcdrv_cache_file.ofs = -1;206 207 return len;208}209 210/**211 * hmcdrv_cache_startup() - startup of HMC drive cache212 * @cachesize: cache size213 *214 * Return: 0 on success, else a (negative) error code215 */216int hmcdrv_cache_startup(size_t cachesize)217{218 if (cachesize > 0) { /* perform caching ? */219 hmcdrv_cache_order = get_order(cachesize);220 hmcdrv_cache_file.content =221 (void *) __get_free_pages(GFP_KERNEL | GFP_DMA,222 hmcdrv_cache_order);223 224 if (!hmcdrv_cache_file.content) {225 pr_err("Allocating the requested cache size of %zu bytes failed\n",226 cachesize);227 return -ENOMEM;228 }229 230 pr_debug("content cache enabled, size is %zu bytes\n",231 cachesize);232 }233 234 hmcdrv_cache_file.len = cachesize;235 return 0;236}237 238/**239 * hmcdrv_cache_shutdown() - shutdown of HMC drive cache240 */241void hmcdrv_cache_shutdown(void)242{243 if (hmcdrv_cache_file.content) {244 free_pages((unsigned long) hmcdrv_cache_file.content,245 hmcdrv_cache_order);246 hmcdrv_cache_file.content = NULL;247 }248 249 hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;250 hmcdrv_cache_file.fsize = LLONG_MAX;251 hmcdrv_cache_file.ofs = -1;252 hmcdrv_cache_file.len = 0; /* no cache */253}254