On Sun, May 01, 2016 at 01:02:55AM +0100, Al Viro wrote:
> I wonder if we ought to put a counter into nfs_cache_array, initialized to 1
> (in nfs_readdir_xdr_to_array()), bumped in get_cache_page() and decremented
> both in cache_page_release() and in ->freepage(). With actual freeing
> of names happening only when the sucker reaches 0, and get_cache_page()
> treating "oops, it's already 0, someone has just evicted it from page cache"
> as "page_cache_release() and retry". Objections?
Something like (completely untested)
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index da109e6..037bfb4 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -145,6 +145,7 @@ struct nfs_cache_array_entry {
};
struct nfs_cache_array {
+ atomic_t refcount;
int size;
int eof_index;
u64 last_cookie;
@@ -200,11 +201,20 @@ void nfs_readdir_clear_array(struct page *page)
int i;
array = kmap_atomic(page);
- for (i = 0; i < array->size; i++)
- kfree(array->array[i].string.name);
+ if (atomic_dec_and_test(&array->refcount))
+ for (i = 0; i < array->size; i++)
+ kfree(array->array[i].string.name);
kunmap_atomic(array);
}
+static bool grab_page(struct page *page)
+{
+ struct nfs_cache_array *array = kmap_atomic(page);
+ bool res = atomic_inc_not_zero(&array->refcount);
+ kunmap_atomic(array);
+ return res;
+}
+
/*
* the caller is responsible for freeing qstr.name
* when called by nfs_readdir_add_to_array, the strings will be freed in
@@ -645,6 +655,7 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
goto out_label_free;
}
memset(array, 0, sizeof(struct nfs_cache_array));
+ atomic_set(&array->refcount, 1);
array->eof_index = -1;
status = nfs_readdir_alloc_pages(pages, array_size);
@@ -707,8 +718,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page* page)
static
void cache_page_release(nfs_readdir_descriptor_t *desc)
{
- if (!desc->page->mapping)
- nfs_readdir_clear_array(desc->page);
+ nfs_readdir_clear_array(desc->page);
page_cache_release(desc->page);
desc->page = NULL;
}
@@ -716,8 +726,16 @@ void cache_page_release(nfs_readdir_descriptor_t *desc)
static
struct page *get_cache_page(nfs_readdir_descriptor_t *desc)
{
- return read_cache_page(file_inode(desc->file)->i_mapping,
+ struct page *page;
+
+ for (;;) {
+ page = read_cache_page(file_inode(desc->file)->i_mapping,
desc->page_index, (filler_t *)nfs_readdir_filler, desc);
+ if (IS_ERR(page) || grab_page(page))
+ break;
+ page_cache_release(page);
+ }
+ return page;
}
/*
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
