dosfs: Remove fat_file_datasync()

The fat_file_datasync() read every cluster of the file into the cache
and then synchronized it step-by-step.  For unmodified buffers this is a
non-operation.  For modified buffers this will wake-up the swapout task
which performs then a single buffer write operation.  This is usually
quite inefficient.  Firstly we do single buffer writes, secondly we
may perform a lot of unnecessary read operations (for huge files this is
really bad), and thirdly this leads likely to cache evictions.

The synchronization procedure is replaced by a simple
rtems_bdbuf_sync_dev().  This has the side-effect that also buffers not
related to the file are synchronized, but since the modified list is
normally short this should be acceptable.

1 files changed, 35 insertions, 81 deletions

diff --git a/cpukit/libfs/src/dosfs/msdos_file.c b/cpukit/libfs/src/dosfs/msdos_file.c
index f68e44f948..176ec8e8db 100644
--- a/cpukit/libfs/src/dosfs/msdos_file.c
+++ b/cpukit/libfs/src/dosfs/msdos_file.c
@@ -27,30 +27,11 @@
 
 #include "msdos.h"
 
-/* msdos_file_close --
- *     Close fat-file which correspondes to the file. If fat-file descriptor
- *     which correspondes to the file is not marked "removed", synchronize
- *     size, first cluster number, write time and date fields of the file.
- *
- * PARAMETERS:
- *     iop - file control block
- *
- * RETURNS:
- *     RC_OK, if file closed successfully, or -1 if error occured (errno set
- *     appropriately)
- */
-int
-msdos_file_close(rtems_libio_t *iop)
+static int
+msdos_file_update(rtems_libio_t *iop)
 {
-    int                rc = RC_OK;
-    rtems_status_code  sc = RTEMS_SUCCESSFUL;
-    msdos_fs_info_t   *fs_info = iop->pathinfo.mt_entry->fs_info;
-    fat_file_fd_t     *fat_fd = iop->pathinfo.node_access;
-
-    sc = rtems_semaphore_obtain(fs_info->vol_sema, RTEMS_WAIT,
-                                MSDOS_VOLUME_SEMAPHORE_TIMEOUT);
-    if (sc != RTEMS_SUCCESSFUL)
-        rtems_set_errno_and_return_minus_one(EIO);
+    int              rc = RC_OK;
+    fat_file_fd_t   *fat_fd = iop->pathinfo.node_access;
 
     /*
      * if fat-file descriptor is not marked as "removed", synchronize
@@ -61,25 +42,51 @@ msdos_file_close(rtems_libio_t *iop)
         rc = msdos_set_first_cluster_num(iop->pathinfo.mt_entry, fat_fd);
         if (rc != RC_OK)
         {
-            rtems_semaphore_release(fs_info->vol_sema);
             return rc;
         }
 
         rc = msdos_set_file_size(iop->pathinfo.mt_entry, fat_fd);
         if (rc != RC_OK)
         {
-            rtems_semaphore_release(fs_info->vol_sema);
             return rc;
         }
 
         rc = msdos_set_dir_wrt_time_and_date(iop->pathinfo.mt_entry, fat_fd);
         if (rc != RC_OK)
         {
-            rtems_semaphore_release(fs_info->vol_sema);
             return rc;
         }
     }
 
+    return rc;
+}
+
+/* msdos_file_close --
+ *     Close fat-file which correspondes to the file. If fat-file descriptor
+ *     which correspondes to the file is not marked "removed", synchronize
+ *     size, first cluster number, write time and date fields of the file.
+ *
+ * PARAMETERS:
+ *     iop - file control block
+ *
+ * RETURNS:
+ *     RC_OK, if file closed successfully, or -1 if error occured (errno set
+ *     appropriately)
+ */
+int
+msdos_file_close(rtems_libio_t *iop)
+{
+    int                rc = RC_OK;
+    rtems_status_code  sc = RTEMS_SUCCESSFUL;
+    msdos_fs_info_t   *fs_info = iop->pathinfo.mt_entry->fs_info;
+
+    sc = rtems_semaphore_obtain(fs_info->vol_sema, RTEMS_WAIT,
+                                MSDOS_VOLUME_SEMAPHORE_TIMEOUT);
+    if (sc != RTEMS_SUCCESSFUL)
+        rtems_set_errno_and_return_minus_one(EIO);
+
+    rc = msdos_file_update(iop);
+
     rtems_semaphore_release(fs_info->vol_sema);
     return rc;
 }
@@ -276,67 +283,14 @@ msdos_file_sync(rtems_libio_t *iop)
     if (sc != RTEMS_SUCCESSFUL)
         rtems_set_errno_and_return_minus_one(EIO);
 
-    /* synchronize file data */
-    rc = fat_file_datasync(iop->pathinfo.mt_entry, fat_fd);
+    rc = msdos_file_update(iop);
     if (rc != RC_OK)
     {
         rtems_semaphore_release(fs_info->vol_sema);
         return rc;
     }
 
-    /*
-     * if fat-file descriptor is not marked "removed" - synchronize file
-     * metadata
-     */
-    if (!FAT_FILE_IS_REMOVED(fat_fd))
-    {
-        rc = msdos_set_first_cluster_num(iop->pathinfo.mt_entry, fat_fd);
-        if (rc != RC_OK)
-        {
-            rtems_semaphore_release(fs_info->vol_sema);
-            return rc;
-        }
-        rc = msdos_set_file_size(iop->pathinfo.mt_entry, fat_fd);
-        if (rc != RC_OK)
-        {
-            rtems_semaphore_release(fs_info->vol_sema);
-            return rc;
-        }
-        rc = msdos_set_dir_wrt_time_and_date(iop->pathinfo.mt_entry, fat_fd);
-        if (rc != RC_OK)
-        {
-            rtems_semaphore_release(fs_info->vol_sema);
-            return rc;
-        }
-    }
-
-    rtems_semaphore_release(fs_info->vol_sema);
-    return RC_OK;
-}
-
-/* msdos_file_datasync --
- *     Synchronize file - synchronize only file data (metadata is letf intact).
- *
- * PARAMETERS:
- *     iop - file control block
- *
- * RETURNS:
- *     RC_OK on success, or -1 if error occured (errno set appropriately)
- */
-int
-msdos_file_datasync(rtems_libio_t *iop)
-{
-    rtems_status_code  sc = RTEMS_SUCCESSFUL;
-    fat_file_fd_t     *fat_fd = iop->pathinfo.node_access;
-    msdos_fs_info_t   *fs_info = iop->pathinfo.mt_entry->fs_info;
-
-    sc = rtems_semaphore_obtain(fs_info->vol_sema, RTEMS_WAIT,
-                                MSDOS_VOLUME_SEMAPHORE_TIMEOUT);
-    if (sc != RTEMS_SUCCESSFUL)
-        rtems_set_errno_and_return_minus_one(EIO);
-
-    /* synchronize file data */
-    fat_file_datasync(iop->pathinfo.mt_entry, fat_fd);
+    rc = msdos_sync_unprotected(fs_info);
 
     rtems_semaphore_release(fs_info->vol_sema);
     return RC_OK;