drivers/s390/char/hmcdrv_cache.c

   1 /*
   2  *    SE/HMC Drive (Read) Cache Functions
   3  *
   4  *    Copyright IBM Corp. 2013
   5  *    Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
   6  *
   7  */
   8
   9 #define KMSG_COMPONENT "hmcdrv"
  10 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  11
  12 #include <linux/kernel.h>
  13 #include <linux/mm.h>
  14 #include <linux/jiffies.h>
  15
  16 #include "hmcdrv_ftp.h"
  17 #include "hmcdrv_cache.h"
  18
  19 #define HMCDRV_CACHE_TIMEOUT            30 /* aging timeout in seconds */
  20
  21 /**
  22  * struct hmcdrv_cache_entry - file cache (only used on read/dir)
  23  * @id: FTP command ID
  24  * @content: kernel-space buffer, 4k aligned
  25  * @len: size of @content cache (0 if caching disabled)
  26  * @ofs: start of content within file (-1 if no cached content)
  27  * @fname: file name
  28  * @fsize: file size
  29  * @timeout: cache timeout in jiffies
  30  *
  31  * Notice that the first three members (id, fname, fsize) are cached on all
  32  * read/dir requests. But content is cached only under some preconditions.
  33  * Uncached content is signalled by a negative value of @ofs.
  34  */
  35 struct hmcdrv_cache_entry {
  36         enum hmcdrv_ftp_cmdid id;
  37         char fname[HMCDRV_FTP_FIDENT_MAX];
  38         size_t fsize;
  39         loff_t ofs;
  40         unsigned long timeout;
  41         void *content;
  42         size_t len;
  43 };
  44
  45 static int hmcdrv_cache_order; /* cache allocated page order */
  46
  47 static struct hmcdrv_cache_entry hmcdrv_cache_file = {
  48         .fsize = SIZE_MAX,
  49         .ofs = -1,
  50         .len = 0,
  51         .fname = {'\0'}
  52 };
  53
  54 /**
  55  * hmcdrv_cache_get() - looks for file data/content in read cache
  56  * @ftp: pointer to FTP command specification
  57  *
  58  * Return: number of bytes read from cache or a negative number if nothing
  59  * in content cache (for the file/cmd specified in @ftp)
  60  */
  61 static ssize_t hmcdrv_cache_get(const struct hmcdrv_ftp_cmdspec *ftp)
  62 {
  63         loff_t pos; /* position in cache (signed) */
  64         ssize_t len;
  65
  66         if ((ftp->id != hmcdrv_cache_file.id) ||
  67             strcmp(hmcdrv_cache_file.fname, ftp->fname))
  68                 return -1;
  69
  70         if (ftp->ofs >= hmcdrv_cache_file.fsize) /* EOF ? */
  71                 return 0;
  72
  73         if ((hmcdrv_cache_file.ofs < 0) || /* has content? */
  74             time_after(jiffies, hmcdrv_cache_file.timeout))
  75                 return -1;
  76
  77         /* there seems to be cached content - calculate the maximum number
  78          * of bytes that can be returned (regarding file size and offset)
  79          */
  80         len = hmcdrv_cache_file.fsize - ftp->ofs;
  81
  82         if (len > ftp->len)
  83                 len = ftp->len;
  84
  85         /* check if the requested chunk falls into our cache (which starts
  86          * at offset 'hmcdrv_cache_file.ofs' in the file of interest)
  87          */
  88         pos = ftp->ofs - hmcdrv_cache_file.ofs;
  89
  90         if ((pos >= 0) &&
  91             ((pos + len) <= hmcdrv_cache_file.len)) {
  92
  93                 memcpy(ftp->buf,
  94                        hmcdrv_cache_file.content + pos,
  95                        len);
  96                 pr_debug("using cached content of '%s', returning %zd/%zd bytes\n",
  97                          hmcdrv_cache_file.fname, len,
  98                          hmcdrv_cache_file.fsize);
  99
 100                 return len;
 101         }
 102
 103         return -1;
 104 }
 105
 106 /**
 107  * hmcdrv_cache_do() - do a HMC drive CD/DVD transfer with cache update
 108  * @ftp: pointer to FTP command specification
 109  * @func: FTP transfer function to be used
 110  *
 111  * Return: number of bytes read/written or a (negative) error code
 112  */
 113 static ssize_t hmcdrv_cache_do(const struct hmcdrv_ftp_cmdspec *ftp,
 114                                hmcdrv_cache_ftpfunc func)
 115 {
 116         ssize_t len;
 117
 118         /* only cache content if the read/dir cache really exists
 119          * (hmcdrv_cache_file.len > 0), is large enough to handle the
 120          * request (hmcdrv_cache_file.len >= ftp->len) and there is a need
 121          * to do so (ftp->len > 0)
 122          */
 123         if ((ftp->len > 0) && (hmcdrv_cache_file.len >= ftp->len)) {
 124
 125                 /* because the cache is not located at ftp->buf, we have to
 126                  * assemble a new HMC drive FTP cmd specification (pointing
 127                  * to our cache, and using the increased size)
 128                  */
 129                 struct hmcdrv_ftp_cmdspec cftp = *ftp; /* make a copy */
 130                 cftp.buf = hmcdrv_cache_file.content;  /* and update */
 131                 cftp.len = hmcdrv_cache_file.len;      /* buffer data */
 132
 133                 len = func(&cftp, &hmcdrv_cache_file.fsize); /* now do */
 134
 135                 if (len > 0) {
 136                         pr_debug("caching %zd bytes content for '%s'\n",
 137                                  len, ftp->fname);
 138
 139                         if (len > ftp->len)
 140                                 len = ftp->len;
 141
 142                         hmcdrv_cache_file.ofs = ftp->ofs;
 143                         hmcdrv_cache_file.timeout = jiffies +
 144                                 HMCDRV_CACHE_TIMEOUT * HZ;
 145                         memcpy(ftp->buf, hmcdrv_cache_file.content, len);
 146                 }
 147         } else {
 148                 len = func(ftp, &hmcdrv_cache_file.fsize);
 149                 hmcdrv_cache_file.ofs = -1; /* invalidate content */
 150         }
 151
 152         if (len > 0) {
 153                 /* cache some file info (FTP command, file name and file
 154                  * size) unconditionally
 155                  */
 156                 strlcpy(hmcdrv_cache_file.fname, ftp->fname,
 157                         HMCDRV_FTP_FIDENT_MAX);
 158                 hmcdrv_cache_file.id = ftp->id;
 159                 pr_debug("caching cmd %d, file size %zu for '%s'\n",
 160                          ftp->id, hmcdrv_cache_file.fsize, ftp->fname);
 161         }
 162
 163         return len;
 164 }
 165
 166 /**
 167  * hmcdrv_cache_cmd() - perform a cached HMC drive CD/DVD transfer
 168  * @ftp: pointer to FTP command specification
 169  * @func: FTP transfer function to be used
 170  *
 171  * Attention: Notice that this function is not reentrant - so the caller
 172  * must ensure exclusive execution.
 173  *
 174  * Return: number of bytes read/written or a (negative) error code
 175  */
 176 ssize_t hmcdrv_cache_cmd(const struct hmcdrv_ftp_cmdspec *ftp,
 177                          hmcdrv_cache_ftpfunc func)
 178 {
 179         ssize_t len;
 180
 181         if ((ftp->id == HMCDRV_FTP_DIR) || /* read cache */
 182             (ftp->id == HMCDRV_FTP_NLIST) ||
 183             (ftp->id == HMCDRV_FTP_GET)) {
 184
 185                 len = hmcdrv_cache_get(ftp);
 186
 187                 if (len >= 0) /* got it from cache ? */
 188                         return len; /* yes */
 189
 190                 len = hmcdrv_cache_do(ftp, func);
 191
 192                 if (len >= 0)
 193                         return len;
 194
 195         } else {
 196                 len = func(ftp, NULL); /* simply do original command */
 197         }
 198
 199         /* invalidate the (read) cache in case there was a write operation
 200          * or an error on read/dir
 201          */
 202         hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
 203         hmcdrv_cache_file.fsize = LLONG_MAX;
 204         hmcdrv_cache_file.ofs = -1;
 205
 206         return len;
 207 }
 208
 209 /**
 210  * hmcdrv_cache_startup() - startup of HMC drive cache
 211  * @cachesize: cache size
 212  *
 213  * Return: 0 on success, else a (negative) error code
 214  */
 215 int hmcdrv_cache_startup(size_t cachesize)
 216 {
 217         if (cachesize > 0) { /* perform caching ? */
 218                 hmcdrv_cache_order = get_order(cachesize);
 219                 hmcdrv_cache_file.content =
 220                         (void *) __get_free_pages(GFP_KERNEL | GFP_DMA,
 221                                                   hmcdrv_cache_order);
 222
 223                 if (!hmcdrv_cache_file.content) {
 224                         pr_err("Allocating the requested cache size of %zu bytes failed\n",
 225                                cachesize);
 226                         return -ENOMEM;
 227                 }
 228
 229                 pr_debug("content cache enabled, size is %zu bytes\n",
 230                          cachesize);
 231         }
 232
 233         hmcdrv_cache_file.len = cachesize;
 234         return 0;
 235 }
 236
 237 /**
 238  * hmcdrv_cache_shutdown() - shutdown of HMC drive cache
 239  */
 240 void hmcdrv_cache_shutdown(void)
 241 {
 242         if (hmcdrv_cache_file.content) {
 243                 free_pages((unsigned long) hmcdrv_cache_file.content,
 244                            hmcdrv_cache_order);
 245                 hmcdrv_cache_file.content = NULL;
 246         }
 247
 248         hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
 249         hmcdrv_cache_file.fsize = LLONG_MAX;
 250         hmcdrv_cache_file.ofs = -1;
 251         hmcdrv_cache_file.len = 0; /* no cache */
 252 }