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253 lines
6.6 KiB
253 lines
6.6 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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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 ([email protected]) |
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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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