[Lucid] SRU: Allow mmc cards to be used with unsafe resume
Stefan Bader
stefan.bader at canonical.com
Sat Apr 3 09:50:07 UTC 2010
SRU Justification:
Impact: On suspend, mmc cards are ejected on suspend and rediscovered at
resume. There seems to be a bug in that in Lucid as a mounted mmc card
causes the suspend to hang. Also ejecting and rediscovering is actually
annoying if the card contains extensions to the home directory or a root
filesystem.
Fix: This is not a real fix, but a workaround. In the Lucid code there is
a compile time only option to allow the mmc/sd card to be mounted and just
get reused on resume. Contrary to the unsafe title there arctually is some
safeguarding code to check the cards id before blindly using it.
The following patch leaves the default as it is now, but allows users to
change the mode with a boot parameter or by writing into the modules parameter
in sysfs.
Testcase: Suspend with mounted SD card hangs on its way down. With removable=0
it will go down and come up without apparent problems.
>From faf4b61efc07ba61195e97b42200331aea030b0d Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben at decadent.org.uk>
Date: Mon, 14 Dec 2009 18:01:29 -0800
Subject: [PATCH] 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.
BugLink: http://bugs.launchpad.net/bugs/477106
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
Cc: Wouter van Heyst <larstiq at larstiq.dyndns.org>
Cc: <linux-mmc at vger.kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry-picked from commit bd68e0838fe85794b06892054772fa013a8d1986 upstream)
Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
---
drivers/mmc/core/Kconfig | 4 +++-
drivers/mmc/core/core.c | 16 ++++++++++++++++
drivers/mmc/core/core.h | 2 ++
drivers/mmc/core/mmc.c | 23 +----------------------
drivers/mmc/core/sd.c | 21 +--------------------
5 files changed, 23 insertions(+), 43 deletions(-)
diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
index ab37a6d..bb22ffd 100644
--- 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 7dab2e5..30acd52 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -48,6 +48,22 @@ 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.
*/
static int mmc_schedule_delayed_work(struct delayed_work *work,
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 67ae6ab..a811c52 100644
--- 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 bfefce3..c111894 100644
--- 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 10b2a4d..fdd414e 100644
--- 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.
*/
--
1.6.3.3
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