pstore: Allow the user to explicitly choose a backend

pstore only allows one backend to be registered at present, but the
system may provide several. Add a parameter to allow the user to choose
which backend will be used rather than just relying on load order.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/Documentation/ABI/testing/pstore b/Documentation/ABI/testing/pstore
index ddf451e..ff1df4e 100644 (file)
--- a/Documentation/ABI/testing/pstore
+++ b/Documentation/ABI/testing/pstore
@@ -39,3 +39,9 @@ Description:  Generic interface to platform dependent persistent storage.
                multiple) files based on the record size of the underlying
                persistent storage until at least this amount is reached.
                Default is 10 Kbytes.
+
+               Pstore only supports one backend at a time. If multiple
+               backends are available, the preferred backend may be
+               set by passing the pstore.backend= argument to the kernel at
+               boot time.
+

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index aa47be7..8789d0c 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2151,6 +2151,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
                        0 = disabled, 1 = enabled (default).
 
+       pstore.backend= Specify the name of the pstore backend to use
+
        pt.             [PARIDE]
                        See Documentation/blockdev/paride.txt.
 

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 49ff1de..c5300ec 100644 (file)
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -37,6 +37,8 @@
 static DEFINE_SPINLOCK(pstore_lock);
 static struct pstore_info *psinfo;
 
+static char *backend;
+
 /* How much of the console log to snapshot */
 static unsigned long kmsg_bytes = 10240;
 
@@ -131,6 +133,12 @@ int pstore_register(struct pstore_info *psi)
                spin_unlock(&pstore_lock);
                return -EBUSY;
        }
+
+       if (backend && strcmp(backend, psi->name)) {
+               spin_unlock(&pstore_lock);
+               return -EINVAL;
+       }
+
        psinfo = psi;
        spin_unlock(&pstore_lock);
 
@@ -208,3 +216,6 @@ int pstore_write(enum pstore_type_id type, char *buf, size_t size)
        return 0;
 }
 EXPORT_SYMBOL_GPL(pstore_write);
+
+module_param(backend, charp, 0444);
+MODULE_PARM_DESC(backend, "Pstore backend to use");