Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 72ddc8f7 authored by Michel Lespinasse's avatar Michel Lespinasse Committed by Linus Torvalds
Browse files

do_wp_page: clarify dirty_page handling 



Reorganize the code so that dirty pages are handled closer to the place
that makes them dirty (handling write fault into shared, writable VMAs).
No behavior changes.

Signed-off-by: default avatarMichel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Theodore Tso <tytso@google.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b009c024

mm/memory.c

+38 −34
Original line number Original line Diff line number Diff line
@@ -2229,8 +2229,45 @@ reuse: 
		entry = maybe_mkwrite(pte_mkdirty(entry), vma);

		entry = maybe_mkwrite(pte_mkdirty(entry), vma);

		if (ptep_set_access_flags(vma, address, page_table, entry,1))

		if (ptep_set_access_flags(vma, address, page_table, entry,1))

			update_mmu_cache(vma, address, page_table);

			update_mmu_cache(vma, address, page_table);

		pte_unmap_unlock(page_table, ptl);

		ret |= VM_FAULT_WRITE;

		ret |= VM_FAULT_WRITE;

		goto unlock;



		if (!dirty_page)

			return ret;



		/*

		 * Yes, Virginia, this is actually required to prevent a race

		 * with clear_page_dirty_for_io() from clearing the page dirty

		 * bit after it clear all dirty ptes, but before a racing

		 * do_wp_page installs a dirty pte.

		 *

		 * do_no_page is protected similarly.

		 */

		if (!page_mkwrite) {

			wait_on_page_locked(dirty_page);

			set_page_dirty_balance(dirty_page, page_mkwrite);

		}

		put_page(dirty_page);

		if (page_mkwrite) {

			struct address_space *mapping = dirty_page->mapping;



			set_page_dirty(dirty_page);

			unlock_page(dirty_page);

			page_cache_release(dirty_page);

			if (mapping)	{

				/*

				 * Some device drivers do not set page.mapping

				 * but still dirty their pages

				 */

				balance_dirty_pages_ratelimited(mapping);

			}

		}



		/* file_update_time outside page_lock */

		if (vma->vm_file)

			file_update_time(vma->vm_file);



		return ret;

	}

	}





	/*

	/*
@@ -2336,39 +2373,6 @@ gotten: 
		page_cache_release(old_page);

		page_cache_release(old_page);

unlock:

unlock:

	pte_unmap_unlock(page_table, ptl);

	pte_unmap_unlock(page_table, ptl);

	if (dirty_page) {

		/*

		 * Yes, Virginia, this is actually required to prevent a race

		 * with clear_page_dirty_for_io() from clearing the page dirty

		 * bit after it clear all dirty ptes, but before a racing

		 * do_wp_page installs a dirty pte.

		 *

		 * do_no_page is protected similarly.

		 */

		if (!page_mkwrite) {

			wait_on_page_locked(dirty_page);

			set_page_dirty_balance(dirty_page, page_mkwrite);

		}

		put_page(dirty_page);

		if (page_mkwrite) {

			struct address_space *mapping = dirty_page->mapping;



			set_page_dirty(dirty_page);

			unlock_page(dirty_page);

			page_cache_release(dirty_page);

			if (mapping)	{

				/*

				 * Some device drivers do not set page.mapping

				 * but still dirty their pages

				 */

				balance_dirty_pages_ratelimited(mapping);

			}

		}



		/* file_update_time outside page_lock */

		if (vma->vm_file)

			file_update_time(vma->vm_file);

	}

	return ret;

	return ret;

oom_free_new:

oom_free_new:

	page_cache_release(new_page);

	page_cache_release(new_page);