[Qemu-devel] [PATCH 04/15] Fold postcopy_ram_discard_range into ram_discard_range

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

I'd created this weird pair of:
  ram_discard_range   that lived in migration/ram.c
     Which is built target-dependent so can access the insides of
     RAMBlock

  postcopy_ram_discard_range
     Which actually does the discard.

Flatten these down into ram_discard_range, this relies on the
CONFIG_MADVISE check to be sure we have the real DONTNEED madvise
rather than the posix variant that isn't guaranteed to discard pages.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 include/migration/postcopy-ram.h |  7 -------
 migration/postcopy-ram.c         | 30 +-----------------------------
 migration/ram.c                  | 12 +++++++++++-
 migration/trace-events           |  2 +-
 4 files changed, 13 insertions(+), 38 deletions(-)

diff --git a/include/migration/postcopy-ram.h b/include/migration/postcopy-ram.h
index b6a7491f..43bbbca 100644
--- a/include/migration/postcopy-ram.h
+++ b/include/migration/postcopy-ram.h
@@ -35,13 +35,6 @@ int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages);
 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
 
 /*
- * Discard the contents of 'length' bytes from 'start'
- * We can assume that if we've been called postcopy_ram_hosttest returned true
- */
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
-                               size_t length);
-
-/*
  * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
  * however leaving it until after precopy means that most of the precopy
  * data is still THPd
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index a40dddb..1e3d22f 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -200,27 +200,6 @@ out:
     return ret;
 }
 
-/**
- * postcopy_ram_discard_range: Discard a range of memory.
- * We can assume that if we've been called postcopy_ram_hosttest returned true.
- *
- * @mis: Current incoming migration state.
- * @start, @length: range of memory to discard.
- *
- * returns: 0 on success.
- */
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
-                               size_t length)
-{
-    trace_postcopy_ram_discard_range(start, length);
-    if (madvise(start, length, MADV_DONTNEED)) {
-        error_report("%s MADV_DONTNEED: %s", __func__, strerror(errno));
-        return -1;
-    }
-
-    return 0;
-}
-
 /*
  * Setup an area of RAM so that it *can* be used for postcopy later; this
  * must be done right at the start prior to pre-copy.
@@ -239,7 +218,7 @@ static int init_range(const char *block_name, void *host_addr,
      * - we're going to get the copy from the source anyway.
      * (Precopy will just overwrite this data, so doesn't need the discard)
      */
-    if (postcopy_ram_discard_range(mis, host_addr, length)) {
+    if (ram_discard_range(mis, block_name, 0, length)) {
         return -1;
     }
 
@@ -658,13 +637,6 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
     return -1;
 }
 
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
-                               size_t length)
-{
-    assert(0);
-    return -1;
-}
-
 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
 {
     assert(0);
diff --git a/migration/ram.c b/migration/ram.c
index c9d8290..fe32836 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1853,6 +1853,8 @@ int ram_discard_range(MigrationIncomingState *mis,
 {
     int ret = -1;
 
+    trace_ram_discard_range(block_name, start, length);
+
     rcu_read_lock();
     RAMBlock *rb = qemu_ram_block_by_name(block_name);
 
@@ -1877,7 +1879,15 @@ int ram_discard_range(MigrationIncomingState *mis,
                          host_endaddr);
             goto err;
         }
-        ret = postcopy_ram_discard_range(mis, host_startaddr, length);
+        errno = ENOTSUP;
+#if defined(CONFIG_MADVISE)
+        ret = qemu_madvise(host_startaddr, length, QEMU_MADV_DONTNEED);
+#endif
+        if (ret) {
+            error_report("ram_discard_range: Failed to discard  range "
+                         "%s:%" PRIx64 " +%zx (%d)",
+                         block_name, start, length, errno);
+        }
     } else {
         error_report("ram_discard_range: Overrun block '%s' (%" PRIu64
                      "/%zx/" RAM_ADDR_FMT")",
diff --git a/migration/trace-events b/migration/trace-events
index 94134f7..6dded4f 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -62,6 +62,7 @@ get_queued_page_not_dirty(const char *block_name, uint64_t tmp_offset, uint64_t
 migration_bitmap_sync_start(void) ""
 migration_bitmap_sync_end(uint64_t dirty_pages) "dirty_pages %" PRIu64
 migration_throttle(void) ""
+ram_discard_range(const char *rbname, uint64_t start, size_t len) "%s: start: %" PRIx64 " %zx"
 ram_load_postcopy_loop(uint64_t addr, int flags) "@%" PRIx64 " %x"
 ram_postcopy_send_discard_bitmap(void) ""
 ram_save_queue_pages(const char *rbname, size_t start, size_t len) "%s: start: %zx len: %zx"
@@ -171,7 +172,6 @@ rdma_start_outgoing_migration_after_rdma_source_init(void) ""
 # migration/postcopy-ram.c
 postcopy_discard_send_finish(const char *ramblock, int nwords, int ncmds) "%s mask words sent=%d in %d commands"
 postcopy_discard_send_range(const char *ramblock, unsigned long start, unsigned long length) "%s:%lx/%lx"
-postcopy_ram_discard_range(void *start, size_t length) "%p,+%zx"
 postcopy_cleanup_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
 postcopy_init_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
 postcopy_nhp_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
-- 
2.9.3