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>

1 files changed, 1 insertions, 20 deletions

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 10b2a4d20f5a..fdd414eded09 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.
  */