Revert "binder_alloc: add missing mmap_lock calls when using the VMA"

commit b15655b12ddca7ade09807f790bafb6fab61b50a upstream.

This reverts commit 1561d3aedb2055491040f88e52e8449e6338ba6b.

This caused a performance regression particularly when pages are getting
reclaimed. We don't need to acquire the mmap_lock to determine when the
binder buffer has been fully initialized. A subsequent patch will bring
back the lockless approach for this.

[cmllamas: resolved trivial conflicts with renaming of alloc->mm]

Fixes: 1561d3aedb20 ("binder_alloc: add missing mmap_lock calls when using the VMA")
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20230502201220.1756319-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 4ad42b0f75cd9fb327df21a28679628dbfd11052..35c0cdfa816b325f348a84b66fe9ca812de6923b 100644 (file)
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -380,15 +380,12 @@ static struct binder_buffer *binder_alloc_new_buf_locked(
        size_t size, data_offsets_size;
        int ret;
 
-       mmap_read_lock(alloc->mm);
        if (!binder_alloc_get_vma(alloc)) {
-               mmap_read_unlock(alloc->mm);
                binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                                   "%d: binder_alloc_buf, no vma\n",
                                   alloc->pid);
                return ERR_PTR(-ESRCH);
        }
-       mmap_read_unlock(alloc->mm);
 
        data_offsets_size = ALIGN(data_size, sizeof(void *)) +
                ALIGN(offsets_size, sizeof(void *));
@@ -916,25 +913,17 @@ void binder_alloc_print_pages(struct seq_file *m,
         * Make sure the binder_alloc is fully initialized, otherwise we might
         * read inconsistent state.
         */
-
-       mmap_read_lock(alloc->mm);
-       if (binder_alloc_get_vma(alloc) == NULL) {
-               mmap_read_unlock(alloc->mm);
-               goto uninitialized;
-       }
-
-       mmap_read_unlock(alloc->mm);
-       for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
-               page = &alloc->pages[i];
-               if (!page->page_ptr)
-                       free++;
-               else if (list_empty(&page->lru))
-                       active++;
-               else
-                       lru++;
+       if (binder_alloc_get_vma(alloc) != NULL) {
+               for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
+                       page = &alloc->pages[i];
+                       if (!page->page_ptr)
+                               free++;
+                       else if (list_empty(&page->lru))
+                               active++;
+                       else
+                               lru++;
+               }
        }
-
-uninitialized:
        mutex_unlock(&alloc->mutex);
        seq_printf(m, "  pages: %d:%d:%d\n", active, lru, free);
        seq_printf(m, "  pages high watermark: %zu\n", alloc->pages_high);