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