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Message-ID: <20140113020132.GO1992@bbox>
Date: Mon, 13 Jan 2014 11:01:32 +0900
From: Minchan Kim <minchan@...nel.org>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Andi Kleen <andi@...stfloor.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Bob Liu <bob.liu@...cle.com>,
Christoph Hellwig <hch@...radead.org>,
Dave Chinner <david@...morbit.com>,
Greg Thelen <gthelen@...gle.com>,
Hugh Dickins <hughd@...gle.com>, Jan Kara <jack@...e.cz>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Luigi Semenzato <semenzato@...gle.com>,
Mel Gorman <mgorman@...e.de>,
Metin Doslu <metin@...usdata.com>,
Michel Lespinasse <walken@...gle.com>,
Ozgun Erdogan <ozgun@...usdata.com>,
Peter Zijlstra <peterz@...radead.org>,
Rik van Riel <riel@...hat.com>,
Roman Gushchin <klamm@...dex-team.ru>,
Ryan Mallon <rmallon@...il.com>, Tejun Heo <tj@...nel.org>,
Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 5/9] mm + fs: prepare for non-page entries in page cache
radix trees
On Fri, Jan 10, 2014 at 01:10:39PM -0500, Johannes Weiner wrote:
> shmem mappings already contain exceptional entries where swap slot
> information is remembered.
>
> To be able to store eviction information for regular page cache,
> prepare every site dealing with the radix trees directly to handle
> entries other than pages.
>
> The common lookup functions will filter out non-page entries and
> return NULL for page cache holes, just as before. But provide a raw
> version of the API which returns non-page entries as well, and switch
> shmem over to use it.
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Reviewed-by: Minchan Kim <minchan@...nel.org>
Below are just nitpicks.
> ---
> fs/btrfs/compression.c | 2 +-
> include/linux/mm.h | 8 ++
> include/linux/pagemap.h | 15 ++--
> include/linux/pagevec.h | 3 +
> include/linux/shmem_fs.h | 1 +
> mm/filemap.c | 196 +++++++++++++++++++++++++++++++++++++++++------
> mm/mincore.c | 20 +++--
> mm/readahead.c | 2 +-
> mm/shmem.c | 97 +++++------------------
> mm/swap.c | 47 ++++++++++++
> mm/truncate.c | 73 ++++++++++++++----
> 11 files changed, 336 insertions(+), 128 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 6aad98cb343f..c88316587900 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -474,7 +474,7 @@ static noinline int add_ra_bio_pages(struct inode *inode,
> rcu_read_lock();
> page = radix_tree_lookup(&mapping->page_tree, pg_index);
> rcu_read_unlock();
> - if (page) {
> + if (page && !radix_tree_exceptional_entry(page)) {
> misses++;
> if (misses > 4)
> break;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8b6e55ee8855..c09ef3ae55bc 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -906,6 +906,14 @@ extern void show_free_areas(unsigned int flags);
> extern bool skip_free_areas_node(unsigned int flags, int nid);
>
> int shmem_zero_setup(struct vm_area_struct *);
> +#ifdef CONFIG_SHMEM
> +bool shmem_mapping(struct address_space *mapping);
> +#else
> +static inline bool shmem_mapping(struct address_space *mapping)
> +{
> + return false;
> +}
> +#endif
>
> extern int can_do_mlock(void);
> extern int user_shm_lock(size_t, struct user_struct *);
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index c73130c607c4..b6854b7c58cb 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -248,12 +248,15 @@ pgoff_t page_cache_next_hole(struct address_space *mapping,
> pgoff_t page_cache_prev_hole(struct address_space *mapping,
> pgoff_t index, unsigned long max_scan);
>
> -extern struct page * find_get_page(struct address_space *mapping,
> - pgoff_t index);
> -extern struct page * find_lock_page(struct address_space *mapping,
> - pgoff_t index);
> -extern struct page * find_or_create_page(struct address_space *mapping,
> - pgoff_t index, gfp_t gfp_mask);
> +struct page *__find_get_page(struct address_space *mapping, pgoff_t offset);
> +struct page *find_get_page(struct address_space *mapping, pgoff_t offset);
> +struct page *__find_lock_page(struct address_space *mapping, pgoff_t offset);
> +struct page *find_lock_page(struct address_space *mapping, pgoff_t offset);
> +struct page *find_or_create_page(struct address_space *mapping, pgoff_t index,
> + gfp_t gfp_mask);
> +unsigned __find_get_pages(struct address_space *mapping, pgoff_t start,
> + unsigned int nr_pages, struct page **pages,
> + pgoff_t *indices);
> unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
> unsigned int nr_pages, struct page **pages);
> unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
> diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
> index e4dbfab37729..3c6b8b1e945b 100644
> --- a/include/linux/pagevec.h
> +++ b/include/linux/pagevec.h
> @@ -22,6 +22,9 @@ struct pagevec {
>
> void __pagevec_release(struct pagevec *pvec);
> void __pagevec_lru_add(struct pagevec *pvec);
> +unsigned __pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
> + pgoff_t start, unsigned nr_pages, pgoff_t *indices);
> +void pagevec_remove_exceptionals(struct pagevec *pvec);
> unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
> pgoff_t start, unsigned nr_pages);
> unsigned pagevec_lookup_tag(struct pagevec *pvec,
> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> index 30aa0dc60d75..deb49609cd36 100644
> --- a/include/linux/shmem_fs.h
> +++ b/include/linux/shmem_fs.h
> @@ -49,6 +49,7 @@ extern struct file *shmem_file_setup(const char *name,
> loff_t size, unsigned long flags);
> extern int shmem_zero_setup(struct vm_area_struct *);
> extern int shmem_lock(struct file *file, int lock, struct user_struct *user);
> +extern bool shmem_mapping(struct address_space *mapping);
> extern void shmem_unlock_mapping(struct address_space *mapping);
> extern struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
> pgoff_t index, gfp_t gfp_mask);
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 0746b7a4658f..23eb3be27205 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -446,6 +446,29 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
> }
> EXPORT_SYMBOL_GPL(replace_page_cache_page);
>
> +static int page_cache_tree_insert(struct address_space *mapping,
> + struct page *page)
> +{
> + void **slot;
> + int error;
> +
> + slot = radix_tree_lookup_slot(&mapping->page_tree, page->index);
> + if (slot) {
> + void *p;
> +
> + p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
> + if (!radix_tree_exceptional_entry(p))
> + return -EEXIST;
> + radix_tree_replace_slot(slot, page);
> + mapping->nrpages++;
> + return 0;
> + }
> + error = radix_tree_insert(&mapping->page_tree, page->index, page);
> + if (!error)
> + mapping->nrpages++;
> + return error;
> +}
> +
> /**
> * add_to_page_cache_locked - add a locked page to the pagecache
> * @page: page to add
> @@ -480,11 +503,10 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
> page->index = offset;
>
> spin_lock_irq(&mapping->tree_lock);
> - error = radix_tree_insert(&mapping->page_tree, offset, page);
> + error = page_cache_tree_insert(mapping, page);
> radix_tree_preload_end();
> if (unlikely(error))
> goto err_insert;
> - mapping->nrpages++;
> __inc_zone_page_state(page, NR_FILE_PAGES);
> spin_unlock_irq(&mapping->tree_lock);
> trace_mm_filemap_add_to_page_cache(page);
> @@ -712,7 +734,10 @@ pgoff_t page_cache_next_hole(struct address_space *mapping,
> unsigned long i;
>
> for (i = 0; i < max_scan; i++) {
> - if (!radix_tree_lookup(&mapping->page_tree, index))
> + struct page *page;
> +
> + page = radix_tree_lookup(&mapping->page_tree, index);
> + if (!page || radix_tree_exceptional_entry(page))
> break;
> index++;
> if (index == 0)
> @@ -750,7 +775,10 @@ pgoff_t page_cache_prev_hole(struct address_space *mapping,
> unsigned long i;
>
> for (i = 0; i < max_scan; i++) {
> - if (!radix_tree_lookup(&mapping->page_tree, index))
> + struct page *page;
> +
> + page = radix_tree_lookup(&mapping->page_tree, index);
> + if (!page || radix_tree_exceptional_entry(page))
> break;
> index--;
> if (index == ULONG_MAX)
> @@ -762,14 +790,19 @@ pgoff_t page_cache_prev_hole(struct address_space *mapping,
> EXPORT_SYMBOL(page_cache_prev_hole);
>
> /**
> - * find_get_page - find and get a page reference
> + * __find_get_page - find and get a page reference
> * @mapping: the address_space to search
> * @offset: the page index
> *
> - * Is there a pagecache struct page at the given (mapping, offset) tuple?
> - * If yes, increment its refcount and return it; if no, return NULL.
> + * Looks up the page cache slot at @mapping & @offset. If there is a
> + * page cache page, it is returned with an increased refcount.
> + *
> + * If the slot holds a shadow entry of a previously evicted page, it
> + * is returned.
> + *
> + * Otherwise, %NULL is returned.
> */
> -struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
> +struct page *__find_get_page(struct address_space *mapping, pgoff_t offset)
> {
> void **pagep;
> struct page *page;
> @@ -810,24 +843,49 @@ out:
>
> return page;
> }
> +EXPORT_SYMBOL(__find_get_page);
> +
> +/**
> + * find_get_page - find and get a page reference
> + * @mapping: the address_space to search
> + * @offset: the page index
> + *
> + * Looks up the page cache slot at @mapping & @offset. If there is a
> + * page cache page, it is returned with an increased refcount.
> + *
> + * Otherwise, %NULL is returned.
> + */
> +struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
> +{
> + struct page *page = __find_get_page(mapping, offset);
> +
> + if (radix_tree_exceptional_entry(page))
> + page = NULL;
> + return page;
> +}
> EXPORT_SYMBOL(find_get_page);
>
> /**
> - * find_lock_page - locate, pin and lock a pagecache page
> + * __find_lock_page - locate, pin and lock a pagecache page
> * @mapping: the address_space to search
> * @offset: the page index
> *
> - * Locates the desired pagecache page, locks it, increments its reference
> - * count and returns its address.
> + * Looks up the page cache slot at @mapping & @offset. If there is a
> + * page cache page, it is returned locked and with an increased
> + * refcount.
> + *
> + * If the slot holds a shadow entry of a previously evicted page, it
> + * is returned.
> + *
> + * Otherwise, %NULL is returned.
> *
> - * Returns zero if the page was not present. find_lock_page() may sleep.
> + * __find_lock_page() may sleep.
> */
> -struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
> +struct page *__find_lock_page(struct address_space *mapping, pgoff_t offset)
> {
> struct page *page;
> -
> repeat:
> - page = find_get_page(mapping, offset);
> + page = __find_get_page(mapping, offset);
> if (page && !radix_tree_exception(page)) {
> lock_page(page);
> /* Has the page been truncated? */
> @@ -840,6 +898,29 @@ repeat:
> }
> return page;
> }
> +EXPORT_SYMBOL(__find_lock_page);
> +
> +/**
> + * find_lock_page - locate, pin and lock a pagecache page
> + * @mapping: the address_space to search
> + * @offset: the page index
> + *
> + * Looks up the page cache slot at @mapping & @offset. If there is a
> + * page cache page, it is returned locked and with an increased
> + * refcount.
> + *
> + * Otherwise, %NULL is returned.
> + *
> + * find_lock_page() may sleep.
> + */
> +struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
> +{
> + struct page *page = __find_lock_page(mapping, offset);
> +
> + if (radix_tree_exceptional_entry(page))
> + page = NULL;
> + return page;
> +}
> EXPORT_SYMBOL(find_lock_page);
>
> /**
> @@ -848,16 +929,18 @@ EXPORT_SYMBOL(find_lock_page);
> * @index: the page's index into the mapping
> * @gfp_mask: page allocation mode
> *
> - * Locates a page in the pagecache. If the page is not present, a new page
> - * is allocated using @gfp_mask and is added to the pagecache and to the VM's
> - * LRU list. The returned page is locked and has its reference count
> - * incremented.
> + * Looks up the page cache slot at @mapping & @offset. If there is a
> + * page cache page, it is returned locked and with an increased
> + * refcount.
> *
> - * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
> - * allocation!
> + * If the page is not present, a new page is allocated using @gfp_mask
> + * and added to the page cache and the VM's LRU list. The page is
> + * returned locked and with an increased refcount.
> *
> - * find_or_create_page() returns the desired page's address, or zero on
> - * memory exhaustion.
> + * On memory exhaustion, %NULL is returned.
> + *
> + * find_or_create_page() may sleep, even if @gfp_flags specifies an
> + * atomic allocation!
> */
> struct page *find_or_create_page(struct address_space *mapping,
> pgoff_t index, gfp_t gfp_mask)
> @@ -890,6 +973,73 @@ repeat:
> EXPORT_SYMBOL(find_or_create_page);
>
> /**
> + * __find_get_pages - gang pagecache lookup
> + * @mapping: The address_space to search
> + * @start: The starting page index
> + * @nr_pages: The maximum number of pages
> + * @pages: Where the resulting pages are placed
where is @indices?
> + *
> + * __find_get_pages() will search for and return a group of up to
> + * @nr_pages pages in the mapping. The pages are placed at @pages.
> + * __find_get_pages() takes a reference against the returned pages.
> + *
> + * The search returns a group of mapping-contiguous pages with ascending
> + * indexes. There may be holes in the indices due to not-present pages.
> + *
> + * Any shadow entries of evicted pages are included in the returned
> + * array.
> + *
> + * __find_get_pages() returns the number of pages and shadow entries
> + * which were found.
> + */
> +unsigned __find_get_pages(struct address_space *mapping,
> + pgoff_t start, unsigned int nr_pages,
> + struct page **pages, pgoff_t *indices)
> +{
> + void **slot;
> + unsigned int ret = 0;
> + struct radix_tree_iter iter;
> +
> + if (!nr_pages)
> + return 0;
> +
> + rcu_read_lock();
> +restart:
> + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
> + struct page *page;
> +repeat:
> + page = radix_tree_deref_slot(slot);
> + if (unlikely(!page))
> + continue;
> + if (radix_tree_exception(page)) {
> + if (radix_tree_deref_retry(page))
> + goto restart;
> + /*
> + * Otherwise, we must be storing a swap entry
> + * here as an exceptional entry: so return it
> + * without attempting to raise page count.
> + */
> + goto export;
> + }
> + if (!page_cache_get_speculative(page))
> + goto repeat;
> +
> + /* Has the page moved? */
> + if (unlikely(page != *slot)) {
> + page_cache_release(page);
> + goto repeat;
> + }
> +export:
> + indices[ret] = iter.index;
> + pages[ret] = page;
> + if (++ret == nr_pages)
> + break;
> + }
> + rcu_read_unlock();
> + return ret;
> +}
> +
> +/**
> * find_get_pages - gang pagecache lookup
> * @mapping: The address_space to search
> * @start: The starting page index
> diff --git a/mm/mincore.c b/mm/mincore.c
> index da2be56a7b8f..ad411ec86a55 100644
> --- a/mm/mincore.c
> +++ b/mm/mincore.c
> @@ -70,13 +70,21 @@ static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
> * any other file mapping (ie. marked !present and faulted in with
> * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
> */
> - page = find_get_page(mapping, pgoff);
> #ifdef CONFIG_SWAP
> - /* shmem/tmpfs may return swap: account for swapcache page too. */
> - if (radix_tree_exceptional_entry(page)) {
> - swp_entry_t swap = radix_to_swp_entry(page);
> - page = find_get_page(swap_address_space(swap), swap.val);
> - }
> + if (shmem_mapping(mapping)) {
> + page = __find_get_page(mapping, pgoff);
> + /*
> + * shmem/tmpfs may return swap: account for swapcache
> + * page too.
> + */
> + if (radix_tree_exceptional_entry(page)) {
> + swp_entry_t swp = radix_to_swp_entry(page);
> + page = find_get_page(swap_address_space(swp), swp.val);
> + }
> + } else
> + page = find_get_page(mapping, pgoff);
> +#else
> + page = find_get_page(mapping, pgoff);
> #endif
> if (page) {
> present = PageUptodate(page);
> diff --git a/mm/readahead.c b/mm/readahead.c
> index 9eeeeda4ac0e..912c00358112 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -179,7 +179,7 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
> rcu_read_lock();
> page = radix_tree_lookup(&mapping->page_tree, page_offset);
> rcu_read_unlock();
> - if (page)
> + if (page && !radix_tree_exceptional_entry(page))
> continue;
>
> page = page_cache_alloc_readahead(mapping);
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 7c67249d6f28..1f4b65f7b831 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -329,56 +329,6 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
> }
>
> /*
> - * Like find_get_pages, but collecting swap entries as well as pages.
> - */
> -static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
> - pgoff_t start, unsigned int nr_pages,
> - struct page **pages, pgoff_t *indices)
> -{
> - void **slot;
> - unsigned int ret = 0;
> - struct radix_tree_iter iter;
> -
> - if (!nr_pages)
> - return 0;
> -
> - rcu_read_lock();
> -restart:
> - radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
> - struct page *page;
> -repeat:
> - page = radix_tree_deref_slot(slot);
> - if (unlikely(!page))
> - continue;
> - if (radix_tree_exception(page)) {
> - if (radix_tree_deref_retry(page))
> - goto restart;
> - /*
> - * Otherwise, we must be storing a swap entry
> - * here as an exceptional entry: so return it
> - * without attempting to raise page count.
> - */
> - goto export;
> - }
> - if (!page_cache_get_speculative(page))
> - goto repeat;
> -
> - /* Has the page moved? */
> - if (unlikely(page != *slot)) {
> - page_cache_release(page);
> - goto repeat;
> - }
> -export:
> - indices[ret] = iter.index;
> - pages[ret] = page;
> - if (++ret == nr_pages)
> - break;
> - }
> - rcu_read_unlock();
> - return ret;
> -}
> -
> -/*
> * Remove swap entry from radix tree, free the swap and its page cache.
> */
> static int shmem_free_swap(struct address_space *mapping,
> @@ -396,21 +346,6 @@ static int shmem_free_swap(struct address_space *mapping,
> }
>
> /*
> - * Pagevec may contain swap entries, so shuffle up pages before releasing.
> - */
> -static void shmem_deswap_pagevec(struct pagevec *pvec)
> -{
> - int i, j;
> -
> - for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
> - struct page *page = pvec->pages[i];
> - if (!radix_tree_exceptional_entry(page))
> - pvec->pages[j++] = page;
> - }
> - pvec->nr = j;
> -}
> -
> -/*
> * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
> */
> void shmem_unlock_mapping(struct address_space *mapping)
> @@ -428,12 +363,12 @@ void shmem_unlock_mapping(struct address_space *mapping)
> * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
> * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
> */
> - pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
> + pvec.nr = __find_get_pages(mapping, index,
> PAGEVEC_SIZE, pvec.pages, indices);
> if (!pvec.nr)
> break;
> index = indices[pvec.nr - 1] + 1;
> - shmem_deswap_pagevec(&pvec);
> + pagevec_remove_exceptionals(&pvec);
> check_move_unevictable_pages(pvec.pages, pvec.nr);
> pagevec_release(&pvec);
> cond_resched();
> @@ -465,9 +400,9 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
> pagevec_init(&pvec, 0);
> index = start;
> while (index < end) {
> - pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
> - min(end - index, (pgoff_t)PAGEVEC_SIZE),
> - pvec.pages, indices);
> + pvec.nr = __find_get_pages(mapping, index,
> + min(end - index, (pgoff_t)PAGEVEC_SIZE),
> + pvec.pages, indices);
> if (!pvec.nr)
> break;
> mem_cgroup_uncharge_start();
> @@ -496,7 +431,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
> }
> unlock_page(page);
> }
> - shmem_deswap_pagevec(&pvec);
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> mem_cgroup_uncharge_end();
> cond_resched();
> @@ -534,9 +469,10 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
> index = start;
> for ( ; ; ) {
> cond_resched();
> - pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
> +
> + pvec.nr = __find_get_pages(mapping, index,
> min(end - index, (pgoff_t)PAGEVEC_SIZE),
> - pvec.pages, indices);
> + pvec.pages, indices);
> if (!pvec.nr) {
> if (index == start || unfalloc)
> break;
> @@ -544,7 +480,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
> continue;
> }
> if ((index == start || unfalloc) && indices[0] >= end) {
> - shmem_deswap_pagevec(&pvec);
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> break;
> }
> @@ -573,7 +509,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
> }
> unlock_page(page);
> }
> - shmem_deswap_pagevec(&pvec);
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> mem_cgroup_uncharge_end();
> index++;
> @@ -1081,7 +1017,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> return -EFBIG;
> repeat:
> swap.val = 0;
> - page = find_lock_page(mapping, index);
> + page = __find_lock_page(mapping, index);
> if (radix_tree_exceptional_entry(page)) {
> swap = radix_to_swp_entry(page);
> page = NULL;
> @@ -1418,6 +1354,11 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
> return inode;
> }
>
> +bool shmem_mapping(struct address_space *mapping)
> +{
> + return mapping->backing_dev_info == &shmem_backing_dev_info;
> +}
> +
> #ifdef CONFIG_TMPFS
> static const struct inode_operations shmem_symlink_inode_operations;
> static const struct inode_operations shmem_short_symlink_operations;
> @@ -1730,7 +1671,7 @@ static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
> pagevec_init(&pvec, 0);
> pvec.nr = 1; /* start small: we may be there already */
> while (!done) {
> - pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
> + pvec.nr = __find_get_pages(mapping, index,
> pvec.nr, pvec.pages, indices);
> if (!pvec.nr) {
> if (whence == SEEK_DATA)
> @@ -1757,7 +1698,7 @@ static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
> break;
> }
> }
> - shmem_deswap_pagevec(&pvec);
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> pvec.nr = PAGEVEC_SIZE;
> cond_resched();
> diff --git a/mm/swap.c b/mm/swap.c
> index 759c3caf44bd..f624e5b4b724 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -894,6 +894,53 @@ EXPORT_SYMBOL(__pagevec_lru_add);
>
> /**
> * pagevec_lookup - gang pagecache lookup
__pagevec_lookup?
> + * @pvec: Where the resulting entries are placed
> + * @mapping: The address_space to search
> + * @start: The starting entry index
> + * @nr_pages: The maximum number of entries
missing @indices?
> + *
> + * pagevec_lookup() will search for and return a group of up to
> + * @nr_pages pages and shadow entries in the mapping. All entries are
> + * placed in @pvec. pagevec_lookup() takes a reference against actual
> + * pages in @pvec.
> + *
> + * The search returns a group of mapping-contiguous entries with
> + * ascending indexes. There may be holes in the indices due to
> + * not-present entries.
> + *
> + * pagevec_lookup() returns the number of entries which were found.
__pagevec_lookup
> + */
> +unsigned __pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
> + pgoff_t start, unsigned nr_pages, pgoff_t *indices)
> +{
> + pvec->nr = __find_get_pages(mapping, start, nr_pages,
> + pvec->pages, indices);
> + return pagevec_count(pvec);
> +}
> +
> +/**
> + * pagevec_remove_exceptionals - pagevec exceptionals pruning
> + * @pvec: The pagevec to prune
> + *
> + * __pagevec_lookup() fills both pages and exceptional radix tree
> + * entries into the pagevec. This function prunes all exceptionals
> + * from @pvec without leaving holes, so that it can be passed on to
> + * other pagevec operations.
> + */
> +void pagevec_remove_exceptionals(struct pagevec *pvec)
> +{
> + int i, j;
> +
> + for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
> + struct page *page = pvec->pages[i];
> + if (!radix_tree_exceptional_entry(page))
> + pvec->pages[j++] = page;
> + }
> + pvec->nr = j;
> +}
> +
> +/**
> + * pagevec_lookup - gang pagecache lookup
> * @pvec: Where the resulting pages are placed
> * @mapping: The address_space to search
> * @start: The starting page index
> diff --git a/mm/truncate.c b/mm/truncate.c
> index 353b683afd6e..b0f4d4bee8ab 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -22,6 +22,22 @@
> #include <linux/cleancache.h>
> #include "internal.h"
>
> +static void clear_exceptional_entry(struct address_space *mapping,
> + pgoff_t index, void *entry)
> +{
> + /* Handled by shmem itself */
> + if (shmem_mapping(mapping))
> + return;
> +
> + spin_lock_irq(&mapping->tree_lock);
> + /*
> + * Regular page slots are stabilized by the page lock even
> + * without the tree itself locked. These unlocked entries
> + * need verification under the tree lock.
> + */
Could you explain why repeated spin_lock with irq disabled isn't problem
in truncation path?
> + radix_tree_delete_item(&mapping->page_tree, index, entry);
> + spin_unlock_irq(&mapping->tree_lock);
> +}
>
> /**
> * do_invalidatepage - invalidate part or all of a page
> @@ -208,6 +224,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
> unsigned int partial_start; /* inclusive */
> unsigned int partial_end; /* exclusive */
> struct pagevec pvec;
> + pgoff_t indices[PAGEVEC_SIZE];
> pgoff_t index;
> int i;
>
> @@ -238,17 +255,23 @@ void truncate_inode_pages_range(struct address_space *mapping,
>
> pagevec_init(&pvec, 0);
> index = start;
> - while (index < end && pagevec_lookup(&pvec, mapping, index,
> - min(end - index, (pgoff_t)PAGEVEC_SIZE))) {
> + while (index < end && __pagevec_lookup(&pvec, mapping, index,
> + min(end - index, (pgoff_t)PAGEVEC_SIZE),
> + indices)) {
> mem_cgroup_uncharge_start();
> for (i = 0; i < pagevec_count(&pvec); i++) {
> struct page *page = pvec.pages[i];
>
> /* We rely upon deletion not changing page->index */
> - index = page->index;
> + index = indices[i];
> if (index >= end)
> break;
>
> + if (radix_tree_exceptional_entry(page)) {
> + clear_exceptional_entry(mapping, index, page);
> + continue;
> + }
> +
> if (!trylock_page(page))
> continue;
> WARN_ON(page->index != index);
> @@ -259,6 +282,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
> truncate_inode_page(mapping, page);
> unlock_page(page);
> }
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> mem_cgroup_uncharge_end();
> cond_resched();
> @@ -307,14 +331,15 @@ void truncate_inode_pages_range(struct address_space *mapping,
> index = start;
> for ( ; ; ) {
> cond_resched();
> - if (!pagevec_lookup(&pvec, mapping, index,
> - min(end - index, (pgoff_t)PAGEVEC_SIZE))) {
> + if (!__pagevec_lookup(&pvec, mapping, index,
> + min(end - index, (pgoff_t)PAGEVEC_SIZE),
> + indices)) {
> if (index == start)
> break;
> index = start;
> continue;
> }
> - if (index == start && pvec.pages[0]->index >= end) {
> + if (index == start && indices[0] >= end) {
> pagevec_release(&pvec);
> break;
> }
> @@ -323,16 +348,22 @@ void truncate_inode_pages_range(struct address_space *mapping,
> struct page *page = pvec.pages[i];
>
> /* We rely upon deletion not changing page->index */
> - index = page->index;
> + index = indices[i];
> if (index >= end)
> break;
>
> + if (radix_tree_exceptional_entry(page)) {
> + clear_exceptional_entry(mapping, index, page);
> + continue;
> + }
> +
> lock_page(page);
> WARN_ON(page->index != index);
> wait_on_page_writeback(page);
> truncate_inode_page(mapping, page);
> unlock_page(page);
> }
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> mem_cgroup_uncharge_end();
> index++;
> @@ -375,6 +406,7 @@ EXPORT_SYMBOL(truncate_inode_pages);
> unsigned long invalidate_mapping_pages(struct address_space *mapping,
> pgoff_t start, pgoff_t end)
> {
> + pgoff_t indices[PAGEVEC_SIZE];
> struct pagevec pvec;
> pgoff_t index = start;
> unsigned long ret;
> @@ -390,17 +422,23 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
> */
>
> pagevec_init(&pvec, 0);
> - while (index <= end && pagevec_lookup(&pvec, mapping, index,
> - min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
> + while (index <= end && __pagevec_lookup(&pvec, mapping, index,
> + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
> + indices)) {
> mem_cgroup_uncharge_start();
> for (i = 0; i < pagevec_count(&pvec); i++) {
> struct page *page = pvec.pages[i];
>
> /* We rely upon deletion not changing page->index */
> - index = page->index;
> + index = indices[i];
> if (index > end)
> break;
>
> + if (radix_tree_exceptional_entry(page)) {
> + clear_exceptional_entry(mapping, index, page);
> + continue;
> + }
> +
> if (!trylock_page(page))
> continue;
> WARN_ON(page->index != index);
> @@ -414,6 +452,7 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
> deactivate_page(page);
> count += ret;
> }
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> mem_cgroup_uncharge_end();
> cond_resched();
> @@ -481,6 +520,7 @@ static int do_launder_page(struct address_space *mapping, struct page *page)
> int invalidate_inode_pages2_range(struct address_space *mapping,
> pgoff_t start, pgoff_t end)
> {
> + pgoff_t indices[PAGEVEC_SIZE];
> struct pagevec pvec;
> pgoff_t index;
> int i;
> @@ -491,17 +531,23 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
> cleancache_invalidate_inode(mapping);
> pagevec_init(&pvec, 0);
> index = start;
> - while (index <= end && pagevec_lookup(&pvec, mapping, index,
> - min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
> + while (index <= end && __pagevec_lookup(&pvec, mapping, index,
> + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
> + indices)) {
> mem_cgroup_uncharge_start();
> for (i = 0; i < pagevec_count(&pvec); i++) {
> struct page *page = pvec.pages[i];
>
> /* We rely upon deletion not changing page->index */
> - index = page->index;
> + index = indices[i];
> if (index > end)
> break;
>
> + if (radix_tree_exceptional_entry(page)) {
> + clear_exceptional_entry(mapping, index, page);
> + continue;
> + }
> +
> lock_page(page);
> WARN_ON(page->index != index);
> if (page->mapping != mapping) {
> @@ -539,6 +585,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
> ret = ret2;
> unlock_page(page);
> }
> + pagevec_remove_exceptionals(&pvec);
> pagevec_release(&pvec);
> mem_cgroup_uncharge_end();
> cond_resched();
> --
> 1.8.4.2
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@...ck.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
--
Kind regards,
Minchan Kim
--
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