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>

2 files changed, 212 insertions, 47 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,
diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
index cf6db6b7662a..8ff8c32fef58 100644
--- a/drivers/acpi/apei/erst.c
+++ b/drivers/acpi/apei/erst.c
@@ -429,6 +429,22 @@ ssize_t erst_get_record_count(void)
 }
 EXPORT_SYMBOL_GPL(erst_get_record_count);
 
+#define ERST_RECORD_ID_CACHE_SIZE_MIN   16
+#define ERST_RECORD_ID_CACHE_SIZE_MAX   1024
+
+struct erst_record_id_cache {
+        struct mutex lock;
+        u64 *entries;
+        int len;
+        int size;
+        int refcount;
+};
+
+static struct erst_record_id_cache erst_record_id_cache = {
+        .lock = __MUTEX_INITIALIZER(erst_record_id_cache.lock),
+        .refcount = 0,
+};
+
 static int __erst_get_next_record_id(u64 *record_id)
 {
         struct apei_exec_context ctx;
@@ -443,26 +459,179 @@ static int __erst_get_next_record_id(u64 *record_id)
         return 0;
 }
 
+int erst_get_record_id_begin(int *pos)
+{
+        int rc;
+
+        if (erst_disable)
+                return -ENODEV;
+
+        rc = mutex_lock_interruptible(&erst_record_id_cache.lock);
+        if (rc)
+                return rc;
+        erst_record_id_cache.refcount++;
+        mutex_unlock(&erst_record_id_cache.lock);
+
+        *pos = 0;
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(erst_get_record_id_begin);
+
+/* erst_record_id_cache.lock must be held by caller */
+static int __erst_record_id_cache_add_one(void)
+{
+        u64 id, prev_id, first_id;
+        int i, rc;
+        u64 *entries;
+        unsigned long flags;
+
+        id = prev_id = first_id = APEI_ERST_INVALID_RECORD_ID;
+retry:
+        raw_spin_lock_irqsave(&erst_lock, flags);
+        rc = __erst_get_next_record_id(&id);
+        raw_spin_unlock_irqrestore(&erst_lock, flags);
+        if (rc == -ENOENT)
+                return 0;
+        if (rc)
+                return rc;
+        if (id == APEI_ERST_INVALID_RECORD_ID)
+                return 0;
+        /* can not skip current ID, or loop back to first ID */
+        if (id == prev_id || id == first_id)
+                return 0;
+        if (first_id == APEI_ERST_INVALID_RECORD_ID)
+                first_id = id;
+        prev_id = id;
+
+        entries = erst_record_id_cache.entries;
+        for (i = 0; i < erst_record_id_cache.len; i++) {
+                if (entries[i] == id)
+                        break;
+        }
+        /* record id already in cache, try next */
+        if (i < erst_record_id_cache.len)
+                goto retry;
+        if (erst_record_id_cache.len >= erst_record_id_cache.size) {
+                int new_size, alloc_size;
+                u64 *new_entries;
+
+                new_size = erst_record_id_cache.size * 2;
+                new_size = clamp_val(new_size, ERST_RECORD_ID_CACHE_SIZE_MIN,
+                                     ERST_RECORD_ID_CACHE_SIZE_MAX);
+                if (new_size <= erst_record_id_cache.size) {
+                        if (printk_ratelimit())
+                                pr_warning(FW_WARN ERST_PFX
+                                           "too many record ID!\n");
+                        return 0;
+                }
+                alloc_size = new_size * sizeof(entries[0]);
+                if (alloc_size < PAGE_SIZE)
+                        new_entries = kmalloc(alloc_size, GFP_KERNEL);
+                else
+                        new_entries = vmalloc(alloc_size);
+                if (!new_entries)
+                        return -ENOMEM;
+                memcpy(new_entries, entries,
+                       erst_record_id_cache.len * sizeof(entries[0]));
+                if (erst_record_id_cache.size < PAGE_SIZE)
+                        kfree(entries);
+                else
+                        vfree(entries);
+                erst_record_id_cache.entries = entries = new_entries;
+                erst_record_id_cache.size = new_size;
+        }
+        entries[i] = id;
+        erst_record_id_cache.len++;
+
+        return 1;
+}
+
 /*
  * Get the record ID of an existing error record on the persistent
  * storage. If there is no error record on the persistent storage, the
  * returned record_id is APEI_ERST_INVALID_RECORD_ID.
  */
-int erst_get_next_record_id(u64 *record_id)
+int erst_get_record_id_next(int *pos, u64 *record_id)
 {
-        int rc;
-        unsigned long flags;
+        int rc = 0;
+        u64 *entries;
 
         if (erst_disable)
                 return -ENODEV;
 
-        raw_spin_lock_irqsave(&erst_lock, flags);
-        rc = __erst_get_next_record_id(record_id);
-        raw_spin_unlock_irqrestore(&erst_lock, flags);
+        /* must be enclosed by erst_get_record_id_begin/end */
+        BUG_ON(!erst_record_id_cache.refcount);
+        BUG_ON(*pos < 0 || *pos > erst_record_id_cache.len);
+
+        mutex_lock(&erst_record_id_cache.lock);
+        entries = erst_record_id_cache.entries;
+        for (; *pos < erst_record_id_cache.len; (*pos)++)
+                if (entries[*pos] != APEI_ERST_INVALID_RECORD_ID)
+                        break;
+        /* found next record id in cache */
+        if (*pos < erst_record_id_cache.len) {
+                *record_id = entries[*pos];
+                (*pos)++;
+                goto out_unlock;
+        }
+
+        /* Try to add one more record ID to cache */
+        rc = __erst_record_id_cache_add_one();
+        if (rc < 0)
+                goto out_unlock;
+        /* successfully add one new ID */
+        if (rc == 1) {
+                *record_id = erst_record_id_cache.entries[*pos];
+                (*pos)++;
+                rc = 0;
+        } else {
+                *pos = -1;
+                *record_id = APEI_ERST_INVALID_RECORD_ID;
+        }
+out_unlock:
+        mutex_unlock(&erst_record_id_cache.lock);
 
         return rc;
 }
-EXPORT_SYMBOL_GPL(erst_get_next_record_id);
+EXPORT_SYMBOL_GPL(erst_get_record_id_next);
+
+/* erst_record_id_cache.lock must be held by caller */
+static void __erst_record_id_cache_compact(void)
+{
+        int i, wpos = 0;
+        u64 *entries;
+
+        if (erst_record_id_cache.refcount)
+                return;
+
+        entries = erst_record_id_cache.entries;
+        for (i = 0; i < erst_record_id_cache.len; i++) {
+                if (entries[i] == APEI_ERST_INVALID_RECORD_ID)
+                        continue;
+                if (wpos != i)
+                        memcpy(&entries[wpos], &entries[i], sizeof(entries[i]));
+                wpos++;
+        }
+        erst_record_id_cache.len = wpos;
+}
+
+void erst_get_record_id_end(void)
+{
+        /*
+         * erst_disable != 0 should be detected by invoker via the
+         * return value of erst_get_record_id_begin/next, so this
+         * function should not be called for erst_disable != 0.
+         */
+        BUG_ON(erst_disable);
+
+        mutex_lock(&erst_record_id_cache.lock);
+        erst_record_id_cache.refcount--;
+        BUG_ON(erst_record_id_cache.refcount < 0);
+        __erst_record_id_cache_compact();
+        mutex_unlock(&erst_record_id_cache.lock);
+}
+EXPORT_SYMBOL_GPL(erst_get_record_id_end);
 
 static int __erst_write_to_storage(u64 offset)
 {
@@ -703,56 +872,34 @@ ssize_t erst_read(u64 record_id, struct cper_record_header *record,
 }
 EXPORT_SYMBOL_GPL(erst_read);
 
-/*
- * If return value > buflen, the buffer size is not big enough,
- * else if return value = 0, there is no more record to read,
- * else if return value < 0, something goes wrong,
- * else everything is OK, and return value is record length
- */
-ssize_t erst_read_next(struct cper_record_header *record, size_t buflen)
-{
-        int rc;
-        ssize_t len;
-        unsigned long flags;
-        u64 record_id;
-
-        if (erst_disable)
-                return -ENODEV;
-
-        raw_spin_lock_irqsave(&erst_lock, flags);
-        rc = __erst_get_next_record_id(&record_id);
-        if (rc) {
-                raw_spin_unlock_irqrestore(&erst_lock, flags);
-                return rc;
-        }
-        /* no more record */
-        if (record_id == APEI_ERST_INVALID_RECORD_ID) {
-                raw_spin_unlock_irqrestore(&erst_lock, flags);
-                return 0;
-        }
-
-        len = __erst_read(record_id, record, buflen);
-        raw_spin_unlock_irqrestore(&erst_lock, flags);
-
-        return len;
-}
-EXPORT_SYMBOL_GPL(erst_read_next);
-
 int erst_clear(u64 record_id)
 {
-        int rc;
+        int rc, i;
         unsigned long flags;
+        u64 *entries;
 
         if (erst_disable)
                 return -ENODEV;
 
+        rc = mutex_lock_interruptible(&erst_record_id_cache.lock);
+        if (rc)
+                return rc;
         raw_spin_lock_irqsave(&erst_lock, flags);
         if (erst_erange.attr & ERST_RANGE_NVRAM)
                 rc = __erst_clear_from_nvram(record_id);
         else
                 rc = __erst_clear_from_storage(record_id);
         raw_spin_unlock_irqrestore(&erst_lock, flags);
-
+        if (rc)
+                goto out;
+        entries = erst_record_id_cache.entries;
+        for (i = 0; i < erst_record_id_cache.len; i++) {
+                if (entries[i] == record_id)
+                        entries[i] = APEI_ERST_INVALID_RECORD_ID;
+        }
+        __erst_record_id_cache_compact();
+out:
+        mutex_unlock(&erst_record_id_cache.lock);
         return rc;
 }
 EXPORT_SYMBOL_GPL(erst_clear);