pstore: fix pstore filesystem mount/remount issue

Currently after mount/remount operation on pstore filesystem,
the content on pstore will be lost. It is because current ERST
implementation doesn't support multi-user usage, which moves
internal pointer to the end after accessing it. Adding
multi-user support for pstore usage.

Signed-off-by: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 35 insertions, 13 deletions

diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
index d5a89d067f98..ddb68c4f8d3e 100644
--- a/drivers/acpi/apei/erst.c
+++ b/drivers/acpi/apei/erst.c
@@ -929,6 +929,8 @@ static int erst_check_table(struct acpi_table_erst *erst_tab)
         return 0;
 }
 
+static int erst_open_pstore(struct pstore_info *psi);
+static int erst_close_pstore(struct pstore_info *psi);
 static ssize_t erst_reader(u64 *id, enum pstore_type_id *type,
                        struct timespec *time);
 static u64 erst_writer(enum pstore_type_id type, size_t size);
@@ -936,6 +938,8 @@ static u64 erst_writer(enum pstore_type_id type, size_t size);
 static struct pstore_info erst_info = {
         .owner          = THIS_MODULE,
         .name           = "erst",
+        .open           = erst_open_pstore,
+        .close          = erst_close_pstore,
         .read           = erst_reader,
         .write          = erst_writer,
         .erase          = erst_clear
@@ -957,12 +961,32 @@ struct cper_pstore_record {
         char data[];
 } __packed;
 
+static int reader_pos;
+
+static int erst_open_pstore(struct pstore_info *psi)
+{
+        int rc;
+
+        if (erst_disable)
+                return -ENODEV;
+
+        rc = erst_get_record_id_begin(&reader_pos);
+
+        return rc;
+}
+
+static int erst_close_pstore(struct pstore_info *psi)
+{
+        erst_get_record_id_end();
+
+        return 0;
+}
+
 static ssize_t erst_reader(u64 *id, enum pstore_type_id *type,
                        struct timespec *time)
 {
         int rc;
-        ssize_t len;
-        unsigned long flags;
+        ssize_t len = 0;
         u64 record_id;
         struct cper_pstore_record *rcd = (struct cper_pstore_record *)
                                         (erst_info.buf - sizeof(*rcd));
@@ -970,24 +994,21 @@ static ssize_t erst_reader(u64 *id, enum pstore_type_id *type,
         if (erst_disable)
                 return -ENODEV;
 
-        raw_spin_lock_irqsave(&erst_lock, flags);
 skip:
-        rc = __erst_get_next_record_id(&record_id);
-        if (rc) {
-                raw_spin_unlock_irqrestore(&erst_lock, flags);
-                return rc;
-        }
+        rc = erst_get_record_id_next(&reader_pos, &record_id);
+        if (rc)
+                goto out;
+
         /* no more record */
         if (record_id == APEI_ERST_INVALID_RECORD_ID) {
-                raw_spin_unlock_irqrestore(&erst_lock, flags);
-                return 0;
+                rc = -1;
+                goto out;
         }
 
-        len = __erst_read(record_id, &rcd->hdr, sizeof(*rcd) +
+        len = erst_read(record_id, &rcd->hdr, sizeof(*rcd) +
                           erst_erange.size);
         if (uuid_le_cmp(rcd->hdr.creator_id, CPER_CREATOR_PSTORE) != 0)
                 goto skip;
-        raw_spin_unlock_irqrestore(&erst_lock, flags);
 
         *id = record_id;
         if (uuid_le_cmp(rcd->sec_hdr.section_type,
@@ -1005,7 +1026,8 @@ skip:
                 time->tv_sec = 0;
         time->tv_nsec = 0;
 
-        return len - sizeof(*rcd);
+out:
+        return (rc < 0) ? rc : (len - sizeof(*rcd));
 }
 
 static u64 erst_writer(enum pstore_type_id type, size_t size)