Re: [PATCH 03/14] mm: Protect operations adding pages to page cache with invalidate_lock
From: Christoph Hellwig <hch@infradead.org>
Date: 2021-07-13 06:25:49
Also in:
ceph-devel, linux-cifs, linux-f2fs-devel, linux-fsdevel, linux-mm, linux-xfs
Subsystem:
memory management, page cache, the rest · Maintainers:
Andrew Morton, Matthew Wilcox, Jan Kara, Linus Torvalds
Still looks good. That being said the additional conditional locking in filemap_fault makes it fall over the readbility cliff for me. Something like this on top of your series would help:
diff --git a/mm/filemap.c b/mm/filemap.c
index fd3f94d36c49..0fad08331cf4 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c@@ -3040,21 +3040,23 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) * Do we have something in the page cache already? */ page = find_get_page(mapping, offset); - if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { + if (likely(page)) { /* - * We found the page, so try async readahead before - * waiting for the lock. + * We found the page, so try async readahead before waiting for + * the lock. */ - fpin = do_async_mmap_readahead(vmf, page); - } else if (!page) { + if (!(vmf->flags & FAULT_FLAG_TRIED)) + fpin = do_async_mmap_readahead(vmf, page); + if (unlikely(!PageUptodate(page))) { + filemap_invalidate_lock_shared(mapping); + mapping_locked = true; + } + } else { /* No page in the page cache at all */ count_vm_event(PGMAJFAULT); count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); ret = VM_FAULT_MAJOR; fpin = do_sync_mmap_readahead(vmf); - } - - if (!page) { retry_find: /* * See comment in filemap_create_page() why we need
@@ -3073,9 +3075,6 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) filemap_invalidate_unlock_shared(mapping); return VM_FAULT_OOM; } - } else if (unlikely(!PageUptodate(page))) { - filemap_invalidate_lock_shared(mapping); - mapping_locked = true; } if (!lock_page_maybe_drop_mmap(vmf, page, &fpin))