From 39f985c8f667c80a3d1eb19d31138032fa36b09e Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Sat, 20 Mar 2021 05:40:38 +0000 Subject: [PATCH 1/3] fs/cachefiles: Remove wait_bit_key layout dependency Cachefiles was relying on wait_page_key and wait_bit_key being the same layout, which is fragile. Now that wait_page_key is exposed in the pagemap.h header, we can remove that fragility A comment on the need to maintain structure layout equivalence was added by Linus[1] and that is no longer applicable. Fixes: 62906027091f ("mm: add PageWaiters indicating tasks are waiting for a page bit") Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Signed-off-by: David Howells Tested-by: kafs-testing@auristor.com cc: linux-cachefs@redhat.com cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20210320054104.1300774-2-willy@infradead.org/ Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3510ca20ece0150af6b10c77a74ff1b5c198e3e2 [1] --- fs/cachefiles/rdwr.c | 7 +++---- include/linux/pagemap.h | 1 - 2 files changed, 3 insertions(+), 5 deletions(-) diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c index e027c718ca01..8ffc40e84a59 100644 --- a/fs/cachefiles/rdwr.c +++ b/fs/cachefiles/rdwr.c @@ -24,17 +24,16 @@ static int cachefiles_read_waiter(wait_queue_entry_t *wait, unsigned mode, container_of(wait, struct cachefiles_one_read, monitor); struct cachefiles_object *object; struct fscache_retrieval *op = monitor->op; - struct wait_bit_key *key = _key; + struct wait_page_key *key = _key; struct page *page = wait->private; ASSERT(key); _enter("{%lu},%u,%d,{%p,%u}", monitor->netfs_page->index, mode, sync, - key->flags, key->bit_nr); + key->page, key->bit_nr); - if (key->flags != &page->flags || - key->bit_nr != PG_locked) + if (key->page != page || key->bit_nr != PG_locked) return 0; _debug("--- monitor %p %lx ---", page, page->flags); diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 20225b067583..8f4daac6eb4b 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -559,7 +559,6 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma, return pgoff; } -/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */ struct wait_page_key { struct page *page; int bit_nr; From e5dbd33218bd8d87ab69f730ab90aed5fab7eb26 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Sat, 20 Mar 2021 05:40:39 +0000 Subject: [PATCH 2/3] mm/writeback: Add wait_on_page_writeback_killable This is the killable version of wait_on_page_writeback. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Signed-off-by: David Howells Tested-by: kafs-testing@auristor.com cc: linux-afs@lists.infradead.org cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20210320054104.1300774-3-willy@infradead.org --- include/linux/pagemap.h | 1 + mm/page-writeback.c | 16 ++++++++++++++++ 2 files changed, 17 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 8f4daac6eb4b..8c9947fd62f3 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -682,6 +682,7 @@ static inline int wait_on_page_locked_killable(struct page *page) int put_and_wait_on_page_locked(struct page *page, int state); void wait_on_page_writeback(struct page *page); +int wait_on_page_writeback_killable(struct page *page); extern void end_page_writeback(struct page *page); void wait_for_stable_page(struct page *page); diff --git a/mm/page-writeback.c b/mm/page-writeback.c index eb34d204d4ee..9e35b636a393 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2833,6 +2833,22 @@ void wait_on_page_writeback(struct page *page) } EXPORT_SYMBOL_GPL(wait_on_page_writeback); +/* + * Wait for a page to complete writeback. Returns -EINTR if we get a + * fatal signal while waiting. + */ +int wait_on_page_writeback_killable(struct page *page) +{ + while (PageWriteback(page)) { + trace_wait_on_page_writeback(page, page_mapping(page)); + if (wait_on_page_bit_killable(page, PG_writeback)) + return -EINTR; + } + + return 0; +} +EXPORT_SYMBOL_GPL(wait_on_page_writeback_killable); + /** * wait_for_stable_page() - wait for writeback to finish, if necessary. * @page: The page to wait on. From 75b69799610c2b909a18e709c402923ea61aedc0 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Sat, 20 Mar 2021 05:40:40 +0000 Subject: [PATCH 3/3] afs: Use wait_on_page_writeback_killable Open-coding this function meant it missed out on the recent bugfix for waiters being woken by a delayed wake event from a previous instantiation of the page[1]. [DH: Changed the patch to use vmf->page rather than variable page which doesn't exist yet upstream] Fixes: 1cf7a1518aef ("afs: Implement shared-writeable mmap") Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Signed-off-by: David Howells Tested-by: kafs-testing@auristor.com cc: linux-afs@lists.infradead.org cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20210320054104.1300774-4-willy@infradead.org Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c2407cf7d22d0c0d94cf20342b3b8f06f1d904e7 [1] --- fs/afs/write.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/afs/write.c b/fs/afs/write.c index c9195fc67fd8..eb737ed63afb 100644 --- a/fs/afs/write.c +++ b/fs/afs/write.c @@ -851,8 +851,7 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf) fscache_wait_on_page_write(vnode->cache, vmf->page); #endif - if (PageWriteback(vmf->page) && - wait_on_page_bit_killable(vmf->page, PG_writeback) < 0) + if (wait_on_page_writeback_killable(vmf->page)) return VM_FAULT_RETRY; if (lock_page_killable(vmf->page) < 0)