From: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
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Linus[1] and that is no longer applicable.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) <willy@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-cachefs@xxxxxxxxxx
cc: linux-mm@xxxxxxxxx
Link: https://lore.kernel.org/r/20210320054104.1300774-2-willy@xxxxxxxxxxxxx/
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;
