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SubjectRe: [PATCH v5 1/2] mm: Allow the page cache to allocate large pages
On Mon 02-09-19 03:23:40, William Kucharski wrote:
> Add an 'order' argument to __page_cache_alloc() and
> do_read_cache_page(). Ensure the allocated pages are compound pages.

Why do we need to touch all the existing callers and change them to use
order 0 when none is actually converted to a different order? This just
seem to add a lot of code churn without a good reason. If anything I
would simply add __page_cache_alloc_order and make __page_cache_alloc
call it with order 0 argument.

Also is it so much to ask callers to provide __GFP_COMP explicitly?

> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Signed-off-by: William Kucharski <william.kucharski@oracle.com>
> Reported-by: kbuild test robot <lkp@intel.com>
> ---
> fs/afs/dir.c | 2 +-
> fs/btrfs/compression.c | 2 +-
> fs/cachefiles/rdwr.c | 4 ++--
> fs/ceph/addr.c | 2 +-
> fs/ceph/file.c | 2 +-
> include/linux/pagemap.h | 10 ++++++----
> mm/filemap.c | 20 +++++++++++---------
> mm/readahead.c | 2 +-
> net/ceph/pagelist.c | 4 ++--
> net/ceph/pagevec.c | 2 +-
> 10 files changed, 27 insertions(+), 23 deletions(-)
>
> diff --git a/fs/afs/dir.c b/fs/afs/dir.c
> index 139b4e3cc946..ca8f8e77e012 100644
> --- a/fs/afs/dir.c
> +++ b/fs/afs/dir.c
> @@ -274,7 +274,7 @@ static struct afs_read *afs_read_dir(struct afs_vnode *dvnode, struct key *key)
> afs_stat_v(dvnode, n_inval);
>
> ret = -ENOMEM;
> - req->pages[i] = __page_cache_alloc(gfp);
> + req->pages[i] = __page_cache_alloc(gfp, 0);
> if (!req->pages[i])
> goto error;
> ret = add_to_page_cache_lru(req->pages[i],
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 60c47b417a4b..5280e7477b7e 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -466,7 +466,7 @@ static noinline int add_ra_bio_pages(struct inode *inode,
> }
>
> page = __page_cache_alloc(mapping_gfp_constraint(mapping,
> - ~__GFP_FS));
> + ~__GFP_FS), 0);
> if (!page)
> break;
>
> diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c
> index 44a3ce1e4ce4..11d30212745f 100644
> --- a/fs/cachefiles/rdwr.c
> +++ b/fs/cachefiles/rdwr.c
> @@ -259,7 +259,7 @@ static int cachefiles_read_backing_file_one(struct cachefiles_object *object,
> goto backing_page_already_present;
>
> if (!newpage) {
> - newpage = __page_cache_alloc(cachefiles_gfp);
> + newpage = __page_cache_alloc(cachefiles_gfp, 0);
> if (!newpage)
> goto nomem_monitor;
> }
> @@ -495,7 +495,7 @@ static int cachefiles_read_backing_file(struct cachefiles_object *object,
> goto backing_page_already_present;
>
> if (!newpage) {
> - newpage = __page_cache_alloc(cachefiles_gfp);
> + newpage = __page_cache_alloc(cachefiles_gfp, 0);
> if (!newpage)
> goto nomem;
> }
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index b3c8b886bf64..7c1c3857fbb9 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -1708,7 +1708,7 @@ int ceph_uninline_data(struct file *filp, struct page *locked_page)
> if (len > PAGE_SIZE)
> len = PAGE_SIZE;
> } else {
> - page = __page_cache_alloc(GFP_NOFS);
> + page = __page_cache_alloc(GFP_NOFS, 0);
> if (!page) {
> err = -ENOMEM;
> goto out;
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 685a03cc4b77..ae58d7c31aa4 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1305,7 +1305,7 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
> struct page *page = NULL;
> loff_t i_size;
> if (retry_op == READ_INLINE) {
> - page = __page_cache_alloc(GFP_KERNEL);
> + page = __page_cache_alloc(GFP_KERNEL, 0);
> if (!page)
> return -ENOMEM;
> }
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index c7552459a15f..92e026d9a6b7 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -208,17 +208,19 @@ static inline int page_cache_add_speculative(struct page *page, int count)
> }
>
> #ifdef CONFIG_NUMA
> -extern struct page *__page_cache_alloc(gfp_t gfp);
> +extern struct page *__page_cache_alloc(gfp_t gfp, unsigned int order);
> #else
> -static inline struct page *__page_cache_alloc(gfp_t gfp)
> +static inline struct page *__page_cache_alloc(gfp_t gfp, unsigned int order)
> {
> - return alloc_pages(gfp, 0);
> + if (order > 0)
> + gfp |= __GFP_COMP;
> + return alloc_pages(gfp, order);
> }
> #endif
>
> static inline struct page *page_cache_alloc(struct address_space *x)
> {
> - return __page_cache_alloc(mapping_gfp_mask(x));
> + return __page_cache_alloc(mapping_gfp_mask(x), 0);
> }
>
> static inline gfp_t readahead_gfp_mask(struct address_space *x)
> diff --git a/mm/filemap.c b/mm/filemap.c
> index d0cf700bf201..38b46fc00855 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -954,22 +954,25 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
> EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
>
> #ifdef CONFIG_NUMA
> -struct page *__page_cache_alloc(gfp_t gfp)
> +struct page *__page_cache_alloc(gfp_t gfp, unsigned int order)
> {
> int n;
> struct page *page;
>
> + if (order > 0)
> + gfp |= __GFP_COMP;
> +
> if (cpuset_do_page_mem_spread()) {
> unsigned int cpuset_mems_cookie;
> do {
> cpuset_mems_cookie = read_mems_allowed_begin();
> n = cpuset_mem_spread_node();
> - page = __alloc_pages_node(n, gfp, 0);
> + page = __alloc_pages_node(n, gfp, order);
> } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
>
> return page;
> }
> - return alloc_pages(gfp, 0);
> + return alloc_pages(gfp, order);
> }
> EXPORT_SYMBOL(__page_cache_alloc);
> #endif
> @@ -1665,7 +1668,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
> if (fgp_flags & FGP_NOFS)
> gfp_mask &= ~__GFP_FS;
>
> - page = __page_cache_alloc(gfp_mask);
> + page = __page_cache_alloc(gfp_mask, 0);
> if (!page)
> return NULL;
>
> @@ -2802,15 +2805,14 @@ static struct page *wait_on_page_read(struct page *page)
> static struct page *do_read_cache_page(struct address_space *mapping,
> pgoff_t index,
> int (*filler)(void *, struct page *),
> - void *data,
> - gfp_t gfp)
> + void *data, unsigned int order, gfp_t gfp)
> {
> struct page *page;
> int err;
> repeat:
> page = find_get_page(mapping, index);
> if (!page) {
> - page = __page_cache_alloc(gfp);
> + page = __page_cache_alloc(gfp, order);
> if (!page)
> return ERR_PTR(-ENOMEM);
> err = add_to_page_cache_lru(page, mapping, index, gfp);
> @@ -2917,7 +2919,7 @@ struct page *read_cache_page(struct address_space *mapping,
> int (*filler)(void *, struct page *),
> void *data)
> {
> - return do_read_cache_page(mapping, index, filler, data,
> + return do_read_cache_page(mapping, index, filler, data, 0,
> mapping_gfp_mask(mapping));
> }
> EXPORT_SYMBOL(read_cache_page);
> @@ -2939,7 +2941,7 @@ struct page *read_cache_page_gfp(struct address_space *mapping,
> pgoff_t index,
> gfp_t gfp)
> {
> - return do_read_cache_page(mapping, index, NULL, NULL, gfp);
> + return do_read_cache_page(mapping, index, NULL, NULL, 0, gfp);
> }
> EXPORT_SYMBOL(read_cache_page_gfp);
>
> diff --git a/mm/readahead.c b/mm/readahead.c
> index 2fe72cd29b47..954760a612ea 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -193,7 +193,7 @@ unsigned int __do_page_cache_readahead(struct address_space *mapping,
> continue;
> }
>
> - page = __page_cache_alloc(gfp_mask);
> + page = __page_cache_alloc(gfp_mask, 0);
> if (!page)
> break;
> page->index = page_offset;
> diff --git a/net/ceph/pagelist.c b/net/ceph/pagelist.c
> index 65e34f78b05d..0c3face908dc 100644
> --- a/net/ceph/pagelist.c
> +++ b/net/ceph/pagelist.c
> @@ -56,7 +56,7 @@ static int ceph_pagelist_addpage(struct ceph_pagelist *pl)
> struct page *page;
>
> if (!pl->num_pages_free) {
> - page = __page_cache_alloc(GFP_NOFS);
> + page = __page_cache_alloc(GFP_NOFS, 0);
> } else {
> page = list_first_entry(&pl->free_list, struct page, lru);
> list_del(&page->lru);
> @@ -107,7 +107,7 @@ int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
> space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT; /* conv to num pages */
>
> while (space > pl->num_pages_free) {
> - struct page *page = __page_cache_alloc(GFP_NOFS);
> + struct page *page = __page_cache_alloc(GFP_NOFS, 0);
> if (!page)
> return -ENOMEM;
> list_add_tail(&page->lru, &pl->free_list);
> diff --git a/net/ceph/pagevec.c b/net/ceph/pagevec.c
> index 64305e7056a1..1d07e639216d 100644
> --- a/net/ceph/pagevec.c
> +++ b/net/ceph/pagevec.c
> @@ -45,7 +45,7 @@ struct page **ceph_alloc_page_vector(int num_pages, gfp_t flags)
> if (!pages)
> return ERR_PTR(-ENOMEM);
> for (i = 0; i < num_pages; i++) {
> - pages[i] = __page_cache_alloc(flags);
> + pages[i] = __page_cache_alloc(flags, 0);
> if (pages[i] == NULL) {
> ceph_release_page_vector(pages, i);
> return ERR_PTR(-ENOMEM);
> --
> 2.21.0

--
Michal Hocko
SUSE Labs

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