Note that if the file got truncated before we locked the page, we retry
at find_get_page(). This is similar to what find_lock_page() would do.
Linus's commit ef00e08e introduced a goto no_cached_page in that simuation,
which seems correct as well but possibly less efficient ?
----------------------- >8 ------------------------
This change introduces a single location where filemap_fault() locks
the desired page. There used to be two such places, depending if the
initial find_get_page() was successful or not.
Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
---
mm/filemap.c | 20 +++++++++++---------
1 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 3d4df44..8ed709a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1539,25 +1539,27 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
* waiting for the lock.
*/
do_async_mmap_readahead(vma, ra, file, page, offset);
- lock_page(page);
-
- /* Did it get truncated? */
- if (unlikely(page->mapping != mapping)) {
- unlock_page(page);
- put_page(page);
- goto no_cached_page;
- }
} else {
/* No page in the page cache at all */
do_sync_mmap_readahead(vma, ra, file, offset);
count_vm_event(PGMAJFAULT);
ret = VM_FAULT_MAJOR;
retry_find:
- page = find_lock_page(mapping, offset);
+ page = find_get_page(mapping, offset);
if (!page)
goto no_cached_page;
}
+ lock_page(page);
+
+ /* Did it get truncated? */
+ if (unlikely(page->mapping != mapping)) {
+ unlock_page(page);
+ put_page(page);
+ goto retry_find;
+ }
+ VM_BUG_ON(page->index != offset);
+
/*
* We have a locked page in the page cache, now we need to check
* that it's up-to-date. If not, it is going to be due to an error.
--
1.7.1
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