1 files changed, 253 insertions, 0 deletions
diff --git a/drivers/s390/char/hmcdrv_cache.c b/drivers/s390/char/hmcdrv_cache.c
new file mode 100644
index 000000000..1f5bdb237
--- /dev/null
+++ b/drivers/s390/char/hmcdrv_cache.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *    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 */
+}