Changeset 3233adb in mainline for uspace/srv/vfs/vfs_pager.c

Timestamp:

2016-09-02T17:43:06Z (8 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

2c2d54a, d078c9b9

Parents:

b1956e3

Message:

Implement simple file pager for private mappings

The pager is extremely simple and can be used to create private mappings
of open files. Changes made via different mappings are not coherent and
are not written back to the underlying file. The pager does not cache
any pages.

File:

• uspace/srv/vfs/vfs_pager.c (modified) (1 diff)

uspace/srv/vfs/vfs_pager.c

@@ -38 +38 @@
 #include "vfs.h"
 #include <async.h>
+#include <fibril_synch.h>
 #include <errno.h>
+#include <as.h>
 
 void vfs_page_in(ipc_callid_t rid, ipc_call_t *request)
 {
-        async_answer_0(rid, ENOTSUP);
+        aoff64_t offset = IPC_GET_ARG1(*request);
+        size_t page_size = IPC_GET_ARG2(*request);
+        int fd = IPC_GET_ARG3(*request);
+        void *page;
+        int rc;
+
+        vfs_file_t *file = vfs_file_get(fd);
+        if (!file) {
+                async_answer_0(rid, ENOENT);
+                return;
+        }
+
+        page = as_area_create(AS_AREA_ANY, page_size,
+            AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE,
+            AS_AREA_UNPAGED);
+
+        if (page == AS_MAP_FAILED) {
+                vfs_file_put(file);
+                async_answer_0(rid, ENOMEM);
+                return;
+        }
+
+        rdwr_io_chunk_t chunk = {
+                .buffer = page,
+                .size = page_size
+        };
+
+        fibril_mutex_lock(&file->lock);
+        file->pos = offset;
+        fibril_mutex_unlock(&file->lock);
+
+        size_t total = 0;
+        do {
+                rc = vfs_rdwr_internal(fd, true, &chunk);
+                if (rc != EOK)
+                        break;
+                if (chunk.size == 0)
+                        break;
+                total += chunk.size;
+                chunk.buffer += chunk.size;
+                chunk.size = page_size - total;
+        } while (total < page_size);
+
+        vfs_file_put(file);
+
+        async_answer_1(rid, rc, (sysarg_t) page);
+
+        /*
+         * FIXME: 
+         * This is just for now until we implement proper page cache
+         * management.  Not keeping the pages around in a cache results in
+         * inherently non-coherent private mappings.
+         */
+        as_area_destroy(page);
 }