| Message ID | 20160501001816.GH25498@ZenIV.linux.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, May 01, 2016 at 01:18:16AM +0100, Al Viro wrote: > 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) No problems after 100 iterations... Folded and pushed. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, 2016-05-01 at 02:08 +0100, Al Viro wrote: > On Sun, May 01, 2016 at 01:18:16AM +0100, Al Viro wrote: > > > > 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) > No problems after 100 iterations... Folded and pushed. Same here. Ran same test vs. your work.lookups branch and it seems fine now. Cheers,
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; } /*