--- /dev/null
+/*
+ * 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 */
+}
Code Review / kvmfornfv.git / blobdiff