253 lines
6.5 KiB
C
253 lines
6.5 KiB
C
/*
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* SE/HMC Drive (Read) Cache Functions
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*
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* Copyright IBM Corp. 2013
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* Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
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*
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*/
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#define KMSG_COMPONENT "hmcdrv"
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#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/jiffies.h>
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#include "hmcdrv_ftp.h"
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#include "hmcdrv_cache.h"
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#define HMCDRV_CACHE_TIMEOUT 30 /* aging timeout in seconds */
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/**
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* struct hmcdrv_cache_entry - file cache (only used on read/dir)
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* @id: FTP command ID
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* @content: kernel-space buffer, 4k aligned
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* @len: size of @content cache (0 if caching disabled)
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* @ofs: start of content within file (-1 if no cached content)
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* @fname: file name
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* @fsize: file size
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* @timeout: cache timeout in jiffies
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*
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* Notice that the first three members (id, fname, fsize) are cached on all
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* read/dir requests. But content is cached only under some preconditions.
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* Uncached content is signalled by a negative value of @ofs.
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*/
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struct hmcdrv_cache_entry {
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enum hmcdrv_ftp_cmdid id;
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char fname[HMCDRV_FTP_FIDENT_MAX];
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size_t fsize;
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loff_t ofs;
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unsigned long timeout;
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void *content;
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size_t len;
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};
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static int hmcdrv_cache_order; /* cache allocated page order */
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static struct hmcdrv_cache_entry hmcdrv_cache_file = {
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.fsize = SIZE_MAX,
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.ofs = -1,
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.len = 0,
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.fname = {'\0'}
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};
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/**
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* hmcdrv_cache_get() - looks for file data/content in read cache
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* @ftp: pointer to FTP command specification
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*
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* Return: number of bytes read from cache or a negative number if nothing
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* in content cache (for the file/cmd specified in @ftp)
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*/
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static ssize_t hmcdrv_cache_get(const struct hmcdrv_ftp_cmdspec *ftp)
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{
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loff_t pos; /* position in cache (signed) */
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ssize_t len;
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if ((ftp->id != hmcdrv_cache_file.id) ||
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strcmp(hmcdrv_cache_file.fname, ftp->fname))
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return -1;
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if (ftp->ofs >= hmcdrv_cache_file.fsize) /* EOF ? */
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return 0;
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if ((hmcdrv_cache_file.ofs < 0) || /* has content? */
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time_after(jiffies, hmcdrv_cache_file.timeout))
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return -1;
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/* there seems to be cached content - calculate the maximum number
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* of bytes that can be returned (regarding file size and offset)
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*/
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len = hmcdrv_cache_file.fsize - ftp->ofs;
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if (len > ftp->len)
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len = ftp->len;
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/* check if the requested chunk falls into our cache (which starts
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* at offset 'hmcdrv_cache_file.ofs' in the file of interest)
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*/
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pos = ftp->ofs - hmcdrv_cache_file.ofs;
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if ((pos >= 0) &&
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((pos + len) <= hmcdrv_cache_file.len)) {
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memcpy(ftp->buf,
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hmcdrv_cache_file.content + pos,
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len);
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pr_debug("using cached content of '%s', returning %zd/%zd bytes\n",
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hmcdrv_cache_file.fname, len,
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hmcdrv_cache_file.fsize);
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return len;
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}
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return -1;
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}
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/**
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* hmcdrv_cache_do() - do a HMC drive CD/DVD transfer with cache update
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* @ftp: pointer to FTP command specification
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* @func: FTP transfer function to be used
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*
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* Return: number of bytes read/written or a (negative) error code
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*/
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static ssize_t hmcdrv_cache_do(const struct hmcdrv_ftp_cmdspec *ftp,
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hmcdrv_cache_ftpfunc func)
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{
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ssize_t len;
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/* only cache content if the read/dir cache really exists
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* (hmcdrv_cache_file.len > 0), is large enough to handle the
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* request (hmcdrv_cache_file.len >= ftp->len) and there is a need
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* to do so (ftp->len > 0)
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*/
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if ((ftp->len > 0) && (hmcdrv_cache_file.len >= ftp->len)) {
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/* because the cache is not located at ftp->buf, we have to
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* assemble a new HMC drive FTP cmd specification (pointing
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* to our cache, and using the increased size)
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*/
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struct hmcdrv_ftp_cmdspec cftp = *ftp; /* make a copy */
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cftp.buf = hmcdrv_cache_file.content; /* and update */
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cftp.len = hmcdrv_cache_file.len; /* buffer data */
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len = func(&cftp, &hmcdrv_cache_file.fsize); /* now do */
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if (len > 0) {
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pr_debug("caching %zd bytes content for '%s'\n",
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len, ftp->fname);
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if (len > ftp->len)
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len = ftp->len;
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hmcdrv_cache_file.ofs = ftp->ofs;
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hmcdrv_cache_file.timeout = jiffies +
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HMCDRV_CACHE_TIMEOUT * HZ;
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memcpy(ftp->buf, hmcdrv_cache_file.content, len);
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}
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} else {
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len = func(ftp, &hmcdrv_cache_file.fsize);
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hmcdrv_cache_file.ofs = -1; /* invalidate content */
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}
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if (len > 0) {
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/* cache some file info (FTP command, file name and file
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* size) unconditionally
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*/
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strlcpy(hmcdrv_cache_file.fname, ftp->fname,
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HMCDRV_FTP_FIDENT_MAX);
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hmcdrv_cache_file.id = ftp->id;
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pr_debug("caching cmd %d, file size %zu for '%s'\n",
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ftp->id, hmcdrv_cache_file.fsize, ftp->fname);
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}
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return len;
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}
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/**
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* hmcdrv_cache_cmd() - perform a cached HMC drive CD/DVD transfer
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* @ftp: pointer to FTP command specification
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* @func: FTP transfer function to be used
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*
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* Attention: Notice that this function is not reentrant - so the caller
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* must ensure exclusive execution.
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*
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* Return: number of bytes read/written or a (negative) error code
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*/
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ssize_t hmcdrv_cache_cmd(const struct hmcdrv_ftp_cmdspec *ftp,
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hmcdrv_cache_ftpfunc func)
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{
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ssize_t len;
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if ((ftp->id == HMCDRV_FTP_DIR) || /* read cache */
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(ftp->id == HMCDRV_FTP_NLIST) ||
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(ftp->id == HMCDRV_FTP_GET)) {
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len = hmcdrv_cache_get(ftp);
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if (len >= 0) /* got it from cache ? */
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return len; /* yes */
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len = hmcdrv_cache_do(ftp, func);
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if (len >= 0)
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return len;
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} else {
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len = func(ftp, NULL); /* simply do original command */
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}
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/* invalidate the (read) cache in case there was a write operation
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* or an error on read/dir
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*/
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hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
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hmcdrv_cache_file.fsize = LLONG_MAX;
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hmcdrv_cache_file.ofs = -1;
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return len;
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}
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/**
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* hmcdrv_cache_startup() - startup of HMC drive cache
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* @cachesize: cache size
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*
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* Return: 0 on success, else a (negative) error code
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*/
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int hmcdrv_cache_startup(size_t cachesize)
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{
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if (cachesize > 0) { /* perform caching ? */
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hmcdrv_cache_order = get_order(cachesize);
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hmcdrv_cache_file.content =
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(void *) __get_free_pages(GFP_KERNEL | GFP_DMA,
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hmcdrv_cache_order);
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if (!hmcdrv_cache_file.content) {
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pr_err("Allocating the requested cache size of %zu bytes failed\n",
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cachesize);
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return -ENOMEM;
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}
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pr_debug("content cache enabled, size is %zu bytes\n",
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cachesize);
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}
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hmcdrv_cache_file.len = cachesize;
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return 0;
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}
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/**
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* hmcdrv_cache_shutdown() - shutdown of HMC drive cache
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*/
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void hmcdrv_cache_shutdown(void)
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{
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if (hmcdrv_cache_file.content) {
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free_pages((unsigned long) hmcdrv_cache_file.content,
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hmcdrv_cache_order);
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hmcdrv_cache_file.content = NULL;
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}
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hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
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hmcdrv_cache_file.fsize = LLONG_MAX;
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hmcdrv_cache_file.ofs = -1;
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hmcdrv_cache_file.len = 0; /* no cache */
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}
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