mmc: add module parameter to set whether cards are assumed removable

Some people run general-purpose distribution kernels on netbooks with
a card that is physically non-removable or logically non-removable
(e.g. used for /home) and cannot be cleanly unmounted during suspend.
Add a module parameter to set whether cards are assumed removable or
non-removable, with the default set by CONFIG_MMC_UNSAFE_RESUME.

In general, it is not possible to tell whether a card present in an MMC
slot after resume is the same that was there before suspend.  So there are
two possible behaviours, each of which will cause data loss in some cases:

CONFIG_MMC_UNSAFE_RESUME=n (default): Cards are assumed to be removed
during suspend.  Any filesystem on them must be unmounted before suspend;
otherwise, buffered writes will be lost.

CONFIG_MMC_UNSAFE_RESUME=y: Cards are assumed to remain present during
suspend.  They must not be swapped during suspend; otherwise, buffered
writes will be flushed to the wrong card.

Currently the choice is made at compile time and this allows that to be
overridden at module load time.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Wouter van Heyst <larstiq@larstiq.dyndns.org>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
index ab37a6d9d32a046d7318b3a89a6358c8456b5ef9..bb22ffd76ef8a2bfba0bbdc29d73faabc51911bc 100644 (file)
--- a/drivers/mmc/core/Kconfig
+++ b/drivers/mmc/core/Kconfig
@@ -3,7 +3,7 @@
 #
 
 config MMC_UNSAFE_RESUME
-       bool "Allow unsafe resume (DANGEROUS)"
+       bool "Assume MMC/SD cards are non-removable (DANGEROUS)"
        help
          If you say Y here, the MMC layer will assume that all cards
          stayed in their respective slots during the suspend. The
@@ -14,3 +14,5 @@ config MMC_UNSAFE_RESUME
          This option is usually just for embedded systems which use
          a MMC/SD card for rootfs. Most people should say N here.
 
+         This option sets a default which can be overridden by the
+         module parameter "removable=0" or "removable=1".

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 7dab2e5f4bc9c87c53779a3d49cf2cb368114ef7..30acd526582162033ec3d35d4f770bfa876a41fd 100644 (file)
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -47,6 +47,22 @@ static struct workqueue_struct *workqueue;
 int use_spi_crc = 1;
 module_param(use_spi_crc, bool, 0);
 
+/*
+ * We normally treat cards as removed during suspend if they are not
+ * known to be on a non-removable bus, to avoid the risk of writing
+ * back data to a different card after resume.  Allow this to be
+ * overridden if necessary.
+ */
+#ifdef CONFIG_MMC_UNSAFE_RESUME
+int mmc_assume_removable;
+#else
+int mmc_assume_removable = 1;
+#endif
+module_param_named(removable, mmc_assume_removable, bool, 0644);
+MODULE_PARM_DESC(
+       removable,
+       "MMC/SD cards are removable and may be removed during suspend");
+
 /*
  * Internal function. Schedule delayed work in the MMC work queue.
  */

diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 67ae6abc4230928242109df7f5ab2c773f2971a3..a811c52a165957219bc55e03f7fbe1faab43379f 100644 (file)
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -54,7 +54,9 @@ int mmc_attach_mmc(struct mmc_host *host, u32 ocr);
 int mmc_attach_sd(struct mmc_host *host, u32 ocr);
 int mmc_attach_sdio(struct mmc_host *host, u32 ocr);
 
+/* Module parameters */
 extern int use_spi_crc;
+extern int mmc_assume_removable;
 
 /* Debugfs information for hosts and cards */
 void mmc_add_host_debugfs(struct mmc_host *host);

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index bfefce365ae788ea93d73382298c915fba72288e..c11189446a1f70cd93bcf778e89a41ca06eeac52 100644 (file)
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -602,25 +602,6 @@ static int mmc_awake(struct mmc_host *host)
        return err;
 }
 
-#ifdef CONFIG_MMC_UNSAFE_RESUME
-
-static const struct mmc_bus_ops mmc_ops = {
-       .awake = mmc_awake,
-       .sleep = mmc_sleep,
-       .remove = mmc_remove,
-       .detect = mmc_detect,
-       .suspend = mmc_suspend,
-       .resume = mmc_resume,
-       .power_restore = mmc_power_restore,
-};
-
-static void mmc_attach_bus_ops(struct mmc_host *host)
-{
-       mmc_attach_bus(host, &mmc_ops);
-}
-
-#else
-
 static const struct mmc_bus_ops mmc_ops = {
        .awake = mmc_awake,
        .sleep = mmc_sleep,
@@ -645,15 +626,13 @@ static void mmc_attach_bus_ops(struct mmc_host *host)
 {
        const struct mmc_bus_ops *bus_ops;
 
-       if (host->caps & MMC_CAP_NONREMOVABLE)
+       if (host->caps & MMC_CAP_NONREMOVABLE || !mmc_assume_removable)
                bus_ops = &mmc_ops_unsafe;
        else
                bus_ops = &mmc_ops;
        mmc_attach_bus(host, bus_ops);
 }
 
-#endif
-
 /*
  * Starting point for MMC card init.
  */

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 10b2a4d20f5a1a6b270592d6b048514126bda96a..fdd414eded09a9eef14968a59d026e369c046aa5 100644 (file)
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -606,23 +606,6 @@ static void mmc_sd_power_restore(struct mmc_host *host)
        mmc_release_host(host);
 }
 
-#ifdef CONFIG_MMC_UNSAFE_RESUME
-
-static const struct mmc_bus_ops mmc_sd_ops = {
-       .remove = mmc_sd_remove,
-       .detect = mmc_sd_detect,
-       .suspend = mmc_sd_suspend,
-       .resume = mmc_sd_resume,
-       .power_restore = mmc_sd_power_restore,
-};
-
-static void mmc_sd_attach_bus_ops(struct mmc_host *host)
-{
-       mmc_attach_bus(host, &mmc_sd_ops);
-}
-
-#else
-
 static const struct mmc_bus_ops mmc_sd_ops = {
        .remove = mmc_sd_remove,
        .detect = mmc_sd_detect,
@@ -643,15 +626,13 @@ static void mmc_sd_attach_bus_ops(struct mmc_host *host)
 {
        const struct mmc_bus_ops *bus_ops;
 
-       if (host->caps & MMC_CAP_NONREMOVABLE)
+       if (host->caps & MMC_CAP_NONREMOVABLE || !mmc_assume_removable)
                bus_ops = &mmc_sd_ops_unsafe;
        else
                bus_ops = &mmc_sd_ops;
        mmc_attach_bus(host, bus_ops);
 }
 
-#endif
-
 /*
  * Starting point for SD card init.
  */