ACPI, APEI, Add ERST record ID cache

APEI ERST firmware interface and implementation has no multiple users
in mind.  For example, if there is four records in storage with ID: 1,
2, 3 and 4, if two ERST readers enumerate the records via
GET_NEXT_RECORD_ID as follow,

reader 1		reader 2
1
			2
3
			4
-1
			-1

where -1 signals there is no more record ID.

Reader 1 has no chance to check record 2 and 4, while reader 2 has no
chance to check record 1 and 3.  And any other GET_NEXT_RECORD_ID will
return -1, that is, other readers will has no chance to check any
record even they are not cleared by anyone.

This makes raw GET_NEXT_RECORD_ID not suitable for used by multiple
users.

To solve the issue, an in-memory ERST record ID cache is designed and
implemented.  When enumerating record ID, the ID returned by
GET_NEXT_RECORD_ID is added into cache in addition to be returned to
caller.  So other readers can check the cache to get all record ID
available.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 21 insertions, 3 deletions

diff --git a/drivers/acpi/apei/erst-dbg.c b/drivers/acpi/apei/erst-dbg.c
index de73caf3cebc..a4cfb64c86a1 100644
--- a/drivers/acpi/apei/erst-dbg.c
+++ b/drivers/acpi/apei/erst-dbg.c
@@ -43,12 +43,27 @@ static DEFINE_MUTEX(erst_dbg_mutex);
 
 static int erst_dbg_open(struct inode *inode, struct file *file)
 {
+        int rc, *pos;
+
         if (erst_disable)
                 return -ENODEV;
 
+        pos = (int *)&file->private_data;
+
+        rc = erst_get_record_id_begin(pos);
+        if (rc)
+                return rc;
+
         return nonseekable_open(inode, file);
 }
 
+static int erst_dbg_release(struct inode *inode, struct file *file)
+{
+        erst_get_record_id_end();
+
+        return 0;
+}
+
 static long erst_dbg_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 {
         int rc;
@@ -79,18 +94,20 @@ static long erst_dbg_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 static ssize_t erst_dbg_read(struct file *filp, char __user *ubuf,
                              size_t usize, loff_t *off)
 {
-        int rc;
+        int rc, *pos;
         ssize_t len = 0;
         u64 id;
 
-        if (*off != 0)
+        if (*off)
                 return -EINVAL;
 
         if (mutex_lock_interruptible(&erst_dbg_mutex) != 0)
                 return -EINTR;
 
+        pos = (int *)&filp->private_data;
+
 retry_next:
-        rc = erst_get_next_record_id(&id);
+        rc = erst_get_record_id_next(pos, &id);
         if (rc)
                 goto out;
         /* no more record */
@@ -181,6 +198,7 @@ out:
 static const struct file_operations erst_dbg_ops = {
         .owner          = THIS_MODULE,
         .open           = erst_dbg_open,
+        .release        = erst_dbg_release,
         .read           = erst_dbg_read,
         .write          = erst_dbg_write,
         .unlocked_ioctl = erst_dbg_ioctl,