Atomic write support for ScaleFlux NVMe SSD's

Author: Qi Wu

mysys/my_atomic_writes.c

@@ -19,7 +19,8 @@ my_bool my_may_have_atomic_write= IF_WIN(1,0);
 
 #ifdef __linux__
 
-my_bool has_shannon_atomic_write= 0, has_fusion_io_atomic_write= 0;
+my_bool has_shannon_atomic_write= 0, has_fusion_io_atomic_write= 0,
+        has_sfx_atomic_write= 0;
 
 #include <sys/ioctl.h>
 
@@ -254,6 +255,109 @@ static my_bool shannon_has_atomic_write(File file, int page_size)
 }
 
 
+/***********************************************************************
+  ScaleFlux
+************************************************************************/
+
+#define SFX_GET_ATOMIC_SIZE  _IO('N', 0x244)
+#define SFX_MAX_DEVICES 32
+#define SFX_NO_ATOMIC_SIZE_YET -2
+
+struct sfx_dev
+{
+  char dev_name[32];
+  dev_t st_dev;
+  int atomic_size;
+};
+
+static struct sfx_dev sfx_devices[SFX_MAX_DEVICES + 1];
+
+/**
+   Check if the system has a ScaleFlux card
+   If card exists, record device numbers to allow us to later check if
+   a given file is on this device.
+   @return TRUE   Card exists
+*/
+
+static my_bool test_if_sfx_card_exists()
+{
+  uint sfx_found_devices = 0;
+  uint dev_num;
+
+  for (dev_num = 0; dev_num < SFX_MAX_DEVICES; dev_num++)
+  {
+    struct stat stat_buff;
+
+    sprintf(sfx_devices[sfx_found_devices].dev_name, "/dev/sfdv%dn1",
+            dev_num);
+    if (lstat(sfx_devices[sfx_found_devices].dev_name,
+                &stat_buff) < 0)
+      break;
+
+    sfx_devices[sfx_found_devices].st_dev= stat_buff.st_rdev;
+    /*
+      The atomic size will be checked on first access. This is needed
+      as a normal user can't open the /dev/sfdvXn1 file
+    */
+    sfx_devices[sfx_found_devices].atomic_size = SFX_NO_ATOMIC_SIZE_YET;
+    if (++sfx_found_devices == SFX_MAX_DEVICES)
+      goto end;
+  }
+end:
+  sfx_devices[sfx_found_devices].st_dev= 0;
+  return sfx_found_devices > 0;
+}
+
+static my_bool sfx_dev_has_atomic_write(struct sfx_dev *dev,
+                                            int page_size)
+{
+  if (dev->atomic_size == SFX_NO_ATOMIC_SIZE_YET)
+  {
+    int fd= open(dev->dev_name, 0);
+    if (fd < 0)
+    {
+      perror("open() failed!");
+      dev->atomic_size= 0;                      /* Don't try again */
+      return FALSE;
+    }
+
+    dev->atomic_size= ioctl(fd, SFX_GET_ATOMIC_SIZE);
+    close(fd);
+  }
+
+  return (page_size <= dev->atomic_size);
+}
+
+
+/**
+   Check if a file is on a ScaleFlux device and that it supports atomic_write
+   @param[in] file              OS file handle
+   @param[in] page_size         page size
+   @return TRUE                 Atomic write supported
+
+   @notes
+   This is called only at first open of a file.  In this case it's doesn't
+   matter so much that we loop over all cards.
+   We update the atomic size on first access.
+*/
+
+static my_bool sfx_has_atomic_write(File file, int page_size)
+{
+  struct sfx_dev *dev;
+  struct stat stat_buff;
+
+  if (fstat(file, &stat_buff) < 0)
+  {
+    return 0;
+  }
+
+  for (dev = sfx_devices; dev->st_dev; dev++)
+  {
+    if (stat_buff.st_dev == dev->st_dev)
+      return sfx_dev_has_atomic_write(dev, page_size);
+  }
+  return 0;
+}
 /***********************************************************************
   Generic atomic write code
 ************************************************************************/
@@ -266,7 +370,8 @@ static my_bool shannon_has_atomic_write(File file, int page_size)
 void my_init_atomic_write(void)
 {
   if ((has_shannon_atomic_write=   test_if_shannon_card_exists()) ||
-      (has_fusion_io_atomic_write= test_if_fusion_io_card_exists()))
+      (has_fusion_io_atomic_write= test_if_fusion_io_card_exists()) ||
+      (has_sfx_atomic_write=       test_if_sfx_card_exists()))
   my_may_have_atomic_write= 1;
 #ifdef TEST_SHANNON
   printf("%s(): has_shannon_atomic_write=%d, my_may_have_atomic_write=%d\n",
@@ -294,6 +399,7 @@ my_bool my_test_if_atomic_write(File handle, int page_size)
 #endif
   if (!my_may_have_atomic_write)
     return 0;
+
   if (has_shannon_atomic_write &&
       shannon_has_atomic_write(handle, page_size))
     return 1;
@@ -302,6 +408,10 @@ my_bool my_test_if_atomic_write(File handle, int page_size)
       fusion_io_has_atomic_write(handle, page_size))
     return 1;
 
+  if (has_sfx_atomic_write &&
+      sfx_has_atomic_write(handle, page_size))
+    return 1;
+
   return 0;
 }