diff -ruN bcache-tools-1.0.8/69-bcache.rules bcache-tools-1.0.8.2/69-bcache.rules

--- bcache-tools-1.0.8/69-bcache.rules	2014-12-04 23:51:24.000000000 +0100

+++ bcache-tools-1.0.8.2/69-bcache.rules	2015-02-07 22:32:35.000000000 +0100

@@ -22,11 +22,14 @@

 RUN+="bcache-register $tempnode"

 LABEL="bcache_backing_end"

-# Cached devices: symlink

-DRIVER=="bcache", ENV{CACHED_UUID}=="?*", \

-        SYMLINK+="bcache/by-uuid/$env{CACHED_UUID}"

-DRIVER=="bcache", ENV{CACHED_LABEL}=="?*", \

-        SYMLINK+="bcache/by-label/$env{CACHED_LABEL}"

+# Handling of cached devices

+DRIVER!="bcache", GOTO="bcache_end"

+

+# Apply kernel cmdline parameters

+RUN+="bcache-params $kernel"

+# Symlink

+ENV{CACHED_UUID}=="?*", SYMLINK+="bcache/by-uuid/$env{CACHED_UUID}"

+ENV{CACHED_LABEL}=="?*", SYMLINK+="bcache/by-label/$env{CACHED_LABEL}"

 LABEL="bcache_end"

diff -ruN bcache-tools-1.0.8/bcache-params.c bcache-tools-1.0.8.2/bcache-params.c

--- bcache-tools-1.0.8/bcache-params.c	1970-01-01 01:00:00.000000000 +0100

+++ bcache-tools-1.0.8.2/bcache-params.c	2015-02-07 22:32:35.000000000 +0100

@@ -0,0 +1,196 @@

+/*

+ * Author: Rolf Fokkens <rolf@rolffokkens.nl>

+ *

+ * GPLv2

+ *

+ * For experimenting (or production) it may be useful to set bcache

+ * parameters in an early stage during boot, for example to tune the

+ * boot performance when the root fs is on a bcache device. The best

+ * moment is right before the root fs is actually mounted, which means

+ * it may need to be done in the initramfs.

+ *

+ * The bcache kernel driver does not support passing kernel cmdline

+ * arguments to it. This udev helper can be excuted from udev rules to

+ * take care of cmdline arguments by changing bcache parameters using

+ * the /sys interface right after a bcache device is brought up. This

+ * works both in the initramfs and later.

+ *

+ * It recognizes cmdline arguments like these:

+ *   bcache=sco:0,crdthr:0,cache/congested_write_threshold_us:0

+ * This means:

+ * - for any bcache device set the following parameters:

+ * - sequential_cutoff (sco) is set to 0

+ * - cache/congested_read_threshold_us (crdthr) is set to 0

+ * - cache/congested_write_threshold_us (cwrthr) is set to 0

+ * Both short aliases (for user convenience) and full parameters can be used,

+ * they are defined in the parm_map below.

+ *

+ * Other parameters are not accepted, because they're not useful or 

+ * potentially harmful (e.g. changing the label, stopping bcache devices)

+ *

+ * Parsing of each kernel cmdline argument is done in a simple way:

+ * - does the argument start with "bcache="? If not: next argument.

+ * - for the rest of the argument, identify "subarguments":

+ *   - is what follows of the form <stringP>:<stringV>? If not: next argument

+ *   - is <stringP> a know parameter name? If not: next subargument

+ *   - process the subargument

+ *   - next subargument

+ */

+

+#include <ctype.h>

+#include <stdio.h>

+#include <unistd.h>

+#include <fcntl.h>

+#include <stdlib.h>

+#include <string.h>

+#include <error.h>

+#include <errno.h>

+

+#ifndef TESTING

+#   define CMDLINE "/proc/cmdline"

+#   define SYSPFX "/sys/block"

+#else

+#   define CMDLINE "/tmp/cmdline"   

+#   define SYSPFX "/tmp"            

+#endif

+

+struct parm_map {

+    char *id;

+    char *full;

+};

+

+/*

+ * The list of kernel cmdline patameters that can be processed by 

+ * bcache-patams.

+ */

+struct parm_map parm_map[] = {

+    { "crdthr",                       "cache/congested_read_threshold_us"  }

+,   { "cwrthr",                       "cache/congested_write_threshold_us" }

+,   { "rdahed",                       "readahead"                          }

+,   { "sctoff",                       "sequential_cutoff"                  }

+,   { "wrbdly",                       "writeback_delay"                    }

+,   { "wrbpct",                       "writeback_percent"                  }

+,   { "wrbupd",                       "writeback_rate_update_seconds"      }

+,   { NULL                          , NULL                                 }

+};

+

+/*

+ * Read characters from fp (/proc/cmdline) into buf until maxlen characters are

+ * read or until a character is read that is in the list of terminators.

+ *

+ * lookaheadp points to the current lookahead symbol, and is returned as such to

+ * the caller.

+ *

+ * When a characters is read that is a terminator charachter, the lookehead is moved

+ * one character ahead and the encountered terminator is returned.

+ *

+ * If for another reason reading characters stops, 0 is returned.

+ */

+int read_until (int *lookaheadp, FILE *fp, char *buf, int maxlen, char *terminators)

+{

+    char *cp = buf, *ep = buf + maxlen;

+    int lookahead = *lookaheadp;

+

+    while (   cp < ep

+           && lookahead != EOF

+           && isprint (lookahead)

+           && !strchr (terminators, lookahead)) {

+        *cp++ = lookahead;

+        lookahead = fgetc (fp);

+    }

+

+    *lookaheadp = lookahead;

+

+    *cp = '\0';

+

+    if (strchr (terminators, lookahead)) {

+        *lookaheadp = fgetc (fp);

+        return lookahead;

+    }

+    return 0;

+}

+

+int main(int argc, char *argv[])

+{

+    char buf[256];

+    int  la, bufsz = sizeof (buf);

+    FILE *fp;

+

+    if (argc != 2) {

+        fprintf (stderr, "bcache-params takes exactly one argument\n");

+        return 1;

+    }

+

+    fp = fopen (CMDLINE, "r");

+    if (fp == NULL) {

+        perror ("Error opening /proc/cmdline");

+        return 1;

+    }

+    /* la is our lookahead character */

+    la = fgetc (fp);

+

+    while (la != EOF) {

+        /* skip any spaces */

+        while (la == ' ') {

+            la = fgetc (fp);

+        }

+        /* stop ehen end of the line */

+        if (la == EOF) break;

+

+        /* process until '=' */

+        if (read_until (&la, fp, buf, bufsz, " =") != '=') goto nextarg;

+        /* did we get a "bcache=" prefix? */

+        if (strcmp (buf, "bcache") != 0) goto nextarg;

+

+        /* process subarguments */

+        for (;;) {

+            struct parm_map *pmp;

+            char sysfile[256];

+            int term, fd;

+

+            /* all subargs start with "<string>:" */

+            if (read_until (&la, fp, buf, bufsz, " :") != ':') goto nextarg;

+

+            /* now identify <string> */

+            for (pmp = parm_map; pmp->id != NULL; pmp++) {

+                if (strcmp (buf, pmp->id)   == 0) break;

+                if (strcmp (buf, pmp->full) == 0) break;

+            }

+            /* no match for <string>? next subargument */

+            if (pmp->id == NULL) {

+                error (0, 0, "Unknown bcache parameter %s", buf);

+            } else {

+                /* Now we know what /sys file to write to */

+                sprintf (sysfile, "%s/%s/bcache/%s", SYSPFX, argv[1], pmp->full);

+             }

+

+            /* What follows is the data to be written */

+            term = read_until (&la, fp, buf, bufsz, " ,");

+

+            if (pmp->id == NULL) goto nextsubarg;

+

+            /* no data identified? next subargument */

+            if (buf[0] == '\0') {

+                error (0, 0, "Missing data for parameter %s(%s)", pmp->full, pmp->id);

+                goto nextsubarg;

+            }

+            /* we're ready to actually write the data */

+            fd = open (sysfile, O_WRONLY);

+            if (fd < 0) {

+                error (0, errno, "Error opening %s", sysfile);

+                goto nextsubarg;

+            }

+            if (dprintf (fd, "%s\n", buf) < 0) {

+                error (0, errno, "Error writing %s to %s", buf, sysfile);

+            }

+            close (fd);

+            /* From here there's the hope for another subargument */

+        nextsubarg:

+            if (term != ',') break;

+        }

+    nextarg:

+        while (la != EOF && la != ' ') la = fgetc (fp);

+    }

+    return 0;

+}

+

diff -ruN bcache-tools-1.0.8/dracut/module-setup.sh bcache-tools-1.0.8.2/dracut/module-setup.sh

--- bcache-tools-1.0.8/dracut/module-setup.sh	2014-12-04 23:51:24.000000000 +0100

+++ bcache-tools-1.0.8.2/dracut/module-setup.sh	2015-02-07 22:32:35.000000000 +0100

@@ -29,6 +29,9 @@

 }

 install() {

-    inst_multiple ${udevdir}/probe-bcache ${udevdir}/bcache-register

+    inst_multiple \

+        ${udevdir}/probe-bcache \

+        ${udevdir}/bcache-register \

+        ${udevdir}/bcache-params

     inst_rules 69-bcache.rules

 }

diff -ruN bcache-tools-1.0.8/.gitignore bcache-tools-1.0.8.2/.gitignore

--- bcache-tools-1.0.8/.gitignore	2014-12-04 23:51:24.000000000 +0100

+++ bcache-tools-1.0.8.2/.gitignore	2015-02-07 22:32:35.000000000 +0100

@@ -1,6 +1,7 @@

 /bcache-super-show

 /bcache-test

 /bcache-register

+/bcache-params

 /make-bcache

 /probe-bcache

 .*

diff -ruN bcache-tools-1.0.8/Makefile bcache-tools-1.0.8.2/Makefile

--- bcache-tools-1.0.8/Makefile	2014-12-04 23:51:24.000000000 +0100

+++ bcache-tools-1.0.8.2/Makefile	2015-02-07 22:32:35.000000000 +0100

@@ -5,11 +5,11 @@

 INSTALL=install

 CFLAGS+=-O2 -Wall -g

-all: make-bcache probe-bcache bcache-super-show bcache-register

+all: make-bcache probe-bcache bcache-super-show bcache-register bcache-params

-install: make-bcache probe-bcache bcache-super-show

+install: make-bcache probe-bcache bcache-super-show bcache-register bcache-params

 	$(INSTALL) -m0755 make-bcache bcache-super-show	$(DESTDIR)${PREFIX}/sbin/

-	$(INSTALL) -m0755 probe-bcache bcache-register		$(DESTDIR)$(UDEVLIBDIR)/

+	$(INSTALL) -m0755 probe-bcache bcache-register bcache-params	$(DESTDIR)$(UDEVLIBDIR)/

 	$(INSTALL) -m0644 69-bcache.rules	$(DESTDIR)$(UDEVLIBDIR)/rules.d/

 	$(INSTALL) -m0644 -- *.8 $(DESTDIR)${PREFIX}/share/man/man8/

 	$(INSTALL) -D -m0755 initramfs/hook	$(DESTDIR)/usr/share/initramfs-tools/hooks/bcache

@@ -30,3 +30,4 @@

 bcache-super-show: CFLAGS += -std=gnu99

 bcache-super-show: bcache.o

 bcache-register: bcache-register.o

+bcache-params: bcache-params.o