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Unverified Commit 440e1675 authored by Alexander Winkowski's avatar Alexander Winkowski Committed by basamaryan
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Revert "BACKPORT: FROMLIST: mm: implement speculative handling in filemap_fault()" 



This reverts commit 9debe341.

Change-Id: I3197cb64766cd5e102794d24c946bb88a8e73652
Signed-off-by: default avatarAlexander Winkowski <dereference23@outlook.com>
parent 873a2dc3

mm/filemap.c

+1 −44
Original line number Diff line number Diff line
@@ -2474,9 +2474,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, 
 * it in the page cache, and handles the special cases reasonably without

 * having a lot of duplicated code.

 *

 * If FAULT_FLAG_SPECULATIVE is set, this function runs with elevated vma

 * refcount and with mmap lock not held.

 * Otherwise, vma->vm_mm->mmap_sem must be held on entry.

 * vma->vm_mm->mmap_sem must be held on entry.

 *

 * If our return value has VM_FAULT_RETRY set, it's because

 * lock_page_or_retry() returned 0.
@@ -2501,47 +2499,6 @@ int filemap_fault(struct vm_fault *vmf) 
	struct page *page;

	int ret = 0;



	if (vmf->flags & FAULT_FLAG_SPECULATIVE) {

		page = find_get_page(mapping, offset);

		if (unlikely(!page) || unlikely(PageReadahead(page)))

			return VM_FAULT_RETRY;



		if (!trylock_page(page))

			return VM_FAULT_RETRY;



		if (unlikely(compound_head(page)->mapping != mapping))

			goto page_unlock;

		VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);

		if (unlikely(!PageUptodate(page)))

			goto page_unlock;



		max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);

		if (unlikely(offset >= max_off))

			goto page_unlock;



		/*

		 * Update readahead mmap_miss statistic.

		 *

		 * Note that we are not sure if finish_fault() will

		 * manage to complete the transaction. If it fails,

		 * we'll come back to filemap_fault() non-speculative

		 * case which will update mmap_miss a second time.

		 * This is not ideal, we would prefer to guarantee the

		 * update will happen exactly once.

		 */

		if (!(vmf->vma->vm_flags & VM_RAND_READ) && ra->ra_pages) {

			unsigned int mmap_miss = READ_ONCE(ra->mmap_miss);

			if (mmap_miss)

				WRITE_ONCE(ra->mmap_miss, --mmap_miss);

		}



		vmf->page = page;

		return VM_FAULT_LOCKED;

page_unlock:

		unlock_page(page);

		return VM_FAULT_RETRY;

	}



	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);

	if (unlikely(offset >= max_off))

		return VM_FAULT_SIGBUS;