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FAILED: patch "[PATCH] Revert "binder_alloc: add missing mmap_lock calls when using" failed to apply to 5.15-stable tree

PATCH [email protected] 1 participant 1 message May 28, 2023

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The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x b15655b12ddca7ade09807f790bafb6fab61b50a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023052842-ability-badness-50c6@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

b15655b12ddc ("Revert "binder_alloc: add missing mmap_lock calls when using the VMA"") e66b77e50522 ("binder: rename alloc->vma_vm_mm to alloc->mm") 50e177c5bfd9 ("Merge 6.0-rc4 into char-misc-next")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b15655b12ddca7ade09807f790bafb6fab61b50a Mon Sep 17 00:00:00 2001
From: Carlos Llamas <[email protected]>
Date: Tue, 2 May 2023 20:12:17 +0000
Subject: [PATCH] Revert "binder_alloc: add missing mmap_lock calls when using
the VMA"

This reverts commit 44e602b4e52f70f04620bbbf4fe46ecb40170bde.

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 44e602b4e52f ("binder_alloc: add missing mmap_lock calls when using the VMA")
Cc Liam Howlett <[email protected]>
Cc Suren Baghdasaryan <[email protected]>
Cc [email protected]
Signed-off-by Carlos Llamas <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Greg Kroah-Hartman <[email protected]>
drivers/android/binder_alloc.c +10 -21
index 55a3c3c2409f..92c814ec44fe 100644
@@ -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);