From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: akpm@linux-foundation.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [PATCH v2 03/46] mm: Add kmap_local_folio()
Date: Tue, 22 Jun 2021 13:15:08 +0100 [thread overview]
Message-ID: <20210622121551.3398730-4-willy@infradead.org> (raw)
In-Reply-To: <20210622121551.3398730-1-willy@infradead.org>
This allows us to map a portion of a folio. Callers can only expect
to access up to the next page boundary.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/highmem-internal.h | 11 +++++++++
include/linux/highmem.h | 38 ++++++++++++++++++++++++++++++++
2 files changed, 49 insertions(+)
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index 7902c7d8b55f..d5d6f930ae1d 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h
@@ -73,6 +73,12 @@ static inline void *kmap_local_page(struct page *page)
return __kmap_local_page_prot(page, kmap_prot);
}
+static inline void *kmap_local_folio(struct folio *folio, size_t offset)
+{
+ struct page *page = folio_page(folio, offset / PAGE_SIZE);
+ return __kmap_local_page_prot(page, kmap_prot) + offset % PAGE_SIZE;
+}
+
static inline void *kmap_local_page_prot(struct page *page, pgprot_t prot)
{
return __kmap_local_page_prot(page, prot);
@@ -160,6 +166,11 @@ static inline void *kmap_local_page(struct page *page)
return page_address(page);
}
+static inline void *kmap_local_folio(struct folio *folio, size_t offset)
+{
+ return page_address(&folio->page) + offset;
+}
+
static inline void *kmap_local_page_prot(struct page *page, pgprot_t prot)
{
return kmap_local_page(page);
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 832b49b50c7b..c7c664e0315b 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -96,6 +96,44 @@ static inline void kmap_flush_unused(void);
*/
static inline void *kmap_local_page(struct page *page);
+/**
+ * kmap_local_folio - Map a page in this folio for temporary usage
+ * @folio: The folio to be mapped.
+ * @offset: The byte offset within the folio.
+ *
+ * Returns: The virtual address of the mapping
+ *
+ * Can be invoked from any context.
+ *
+ * Requires careful handling when nesting multiple mappings because the map
+ * management is stack based. The unmap has to be in the reverse order of
+ * the map operation:
+ *
+ * addr1 = kmap_local_folio(page1, offset1);
+ * addr2 = kmap_local_folio(page2, offset2);
+ * ...
+ * kunmap_local(addr2);
+ * kunmap_local(addr1);
+ *
+ * Unmapping addr1 before addr2 is invalid and causes malfunction.
+ *
+ * Contrary to kmap() mappings the mapping is only valid in the context of
+ * the caller and cannot be handed to other contexts.
+ *
+ * On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
+ * virtual address of the direct mapping. Only real highmem pages are
+ * temporarily mapped.
+ *
+ * While it is significantly faster than kmap() for the higmem case it
+ * comes with restrictions about the pointer validity. Only use when really
+ * necessary.
+ *
+ * On HIGHMEM enabled systems mapping a highmem page has the side effect of
+ * disabling migration in order to keep the virtual address stable across
+ * preemption. No caller of kmap_local_folio() can rely on this side effect.
+ */
+static inline void *kmap_local_folio(struct folio *folio, size_t offset);
+
/**
* kmap_atomic - Atomically map a page for temporary usage - Deprecated!
* @page: Pointer to the page to be mapped
--
2.30.2
next prev parent reply other threads:[~2021-06-22 12:20 UTC|newest]
Thread overview: 128+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 12:15 [PATCH v2 00/46] Folio-enabling the page cache Matthew Wilcox (Oracle)
2021-06-22 12:15 ` [PATCH v2 01/46] mm: Add folio_to_pfn() Matthew Wilcox (Oracle)
2021-06-23 7:49 ` Christoph Hellwig
2021-06-24 15:12 ` Matthew Wilcox
2021-06-28 6:18 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 02/46] mm: Add folio_rmapping() Matthew Wilcox (Oracle)
2021-06-23 7:56 ` Christoph Hellwig
2021-06-24 15:51 ` Matthew Wilcox
2021-06-22 12:15 ` Matthew Wilcox (Oracle) [this message]
2021-06-23 7:58 ` [PATCH v2 03/46] mm: Add kmap_local_folio() Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 04/46] mm: Add flush_dcache_folio() Matthew Wilcox (Oracle)
2021-06-22 12:15 ` [PATCH v2 05/46] mm: Add arch_make_folio_accessible() Matthew Wilcox (Oracle)
2021-06-23 8:00 ` Christoph Hellwig
2021-06-24 15:57 ` Matthew Wilcox
2021-06-28 6:21 ` Christoph Hellwig
2021-06-28 14:07 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 06/46] mm: Add folio_young() and folio_idle() Matthew Wilcox (Oracle)
2021-06-22 12:15 ` [PATCH v2 07/46] mm/workingset: Convert workingset_activation to take a folio Matthew Wilcox (Oracle)
2021-06-23 8:02 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 08/46] mm/swap: Add folio_activate() Matthew Wilcox (Oracle)
2021-06-23 8:04 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 09/46] mm/swap: Add folio_mark_accessed() Matthew Wilcox (Oracle)
2021-06-23 8:07 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 10/46] mm/rmap: Add folio_mkclean() Matthew Wilcox (Oracle)
2021-06-23 8:08 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 11/46] mm/memcg: Remove 'page' parameter to mem_cgroup_charge_statistics() Matthew Wilcox (Oracle)
2021-06-23 8:09 ` Christoph Hellwig
2021-06-25 7:58 ` Michal Hocko
2021-06-22 12:15 ` [PATCH v2 12/46] mm/memcg: Use the node id in mem_cgroup_update_tree() Matthew Wilcox (Oracle)
2021-06-23 8:12 ` Christoph Hellwig
2021-06-24 16:19 ` Matthew Wilcox
2021-06-25 8:05 ` Michal Hocko
2021-06-22 12:15 ` [PATCH v2 13/46] mm/memcg: Convert commit_charge() to take a folio Matthew Wilcox (Oracle)
2021-06-23 8:13 ` Christoph Hellwig
2021-06-25 8:11 ` Michal Hocko
2021-06-22 12:15 ` [PATCH v2 14/46] mm/memcg: Add folio_charge_cgroup() Matthew Wilcox (Oracle)
2021-06-23 8:15 ` Christoph Hellwig
2021-06-24 16:42 ` Matthew Wilcox
2021-06-25 8:22 ` Michal Hocko
2021-06-25 11:34 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 15/46] mm/memcg: Add folio_uncharge_cgroup() Matthew Wilcox (Oracle)
2021-06-23 8:16 ` Christoph Hellwig
2021-06-25 8:25 ` Michal Hocko
2021-06-25 11:21 ` Matthew Wilcox
2021-06-25 13:21 ` Michal Hocko
2021-06-22 12:15 ` [PATCH v2 16/46] mm/memcg: Add folio_migrate_cgroup() Matthew Wilcox (Oracle)
2021-06-23 8:19 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 17/46] mm/memcg: Convert mem_cgroup_track_foreign_dirty_slowpath() to folio Matthew Wilcox (Oracle)
2021-06-23 8:21 ` Christoph Hellwig
2021-06-24 17:37 ` Matthew Wilcox
2021-06-28 6:24 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 18/46] mm/migrate: Add folio_migrate_mapping() Matthew Wilcox (Oracle)
2021-06-23 8:22 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 19/46] mm/migrate: Add folio_migrate_flags() Matthew Wilcox (Oracle)
2021-06-23 8:28 ` Christoph Hellwig
2021-06-24 17:55 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 20/46] mm/migrate: Add folio_migrate_copy() Matthew Wilcox (Oracle)
2021-06-23 8:35 ` Christoph Hellwig
2021-06-24 18:02 ` Matthew Wilcox
2021-06-28 6:26 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 21/46] mm/writeback: Rename __add_wb_stat() to wb_stat_mod() Matthew Wilcox (Oracle)
2021-06-23 8:37 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 22/46] flex_proportions: Allow N events instead of 1 Matthew Wilcox (Oracle)
2021-06-23 8:41 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 23/46] mm/writeback: Change __wb_writeout_inc() to __wb_writeout_add() Matthew Wilcox (Oracle)
2021-06-23 8:45 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 24/46] mm/writeback: Add __folio_end_writeback() Matthew Wilcox (Oracle)
2021-06-23 9:15 ` Christoph Hellwig
2021-06-24 18:20 ` Matthew Wilcox
2021-06-28 6:33 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 25/46] mm/writeback: Add folio_start_writeback() Matthew Wilcox (Oracle)
2021-06-23 9:18 ` Christoph Hellwig
2021-06-24 18:33 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 26/46] mm/writeback: Add folio_mark_dirty() Matthew Wilcox (Oracle)
2021-06-23 9:21 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 27/46] mm/writeback: Add __folio_mark_dirty() Matthew Wilcox (Oracle)
2021-06-23 9:27 ` Christoph Hellwig
2021-06-24 18:37 ` Matthew Wilcox
2021-06-28 6:03 ` Christoph Hellwig
2021-06-28 15:43 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 28/46] mm/writeback: Add filemap_dirty_folio() Matthew Wilcox (Oracle)
2021-06-23 9:32 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 29/46] mm/writeback: Add folio_account_cleaned() Matthew Wilcox (Oracle)
2021-06-23 9:36 ` Christoph Hellwig
2021-06-24 20:06 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 30/46] mm/writeback: Add folio_cancel_dirty() Matthew Wilcox (Oracle)
2021-06-23 9:39 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 31/46] mm/writeback: Add folio_clear_dirty_for_io() Matthew Wilcox (Oracle)
2021-06-23 9:43 ` Christoph Hellwig
2021-06-24 20:09 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 32/46] mm/writeback: Add folio_account_redirty() Matthew Wilcox (Oracle)
2021-06-23 9:44 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 33/46] mm/writeback: Add folio_redirty_for_writepage() Matthew Wilcox (Oracle)
2021-06-23 9:45 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 34/46] mm/filemap: Add i_blocks_per_folio() Matthew Wilcox (Oracle)
2021-06-23 9:46 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 35/46] mm/filemap: Add folio_mkwrite_check_truncate() Matthew Wilcox (Oracle)
2021-06-23 9:47 ` Christoph Hellwig
2021-06-23 13:19 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 36/46] mm/filemap: Add readahead_folio() Matthew Wilcox (Oracle)
2021-06-23 9:50 ` Christoph Hellwig
2021-06-24 23:46 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 37/46] mm/workingset: Convert workingset_refault() to take a folio Matthew Wilcox (Oracle)
2021-06-23 9:52 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 38/46] mm: Add folio_evictable() Matthew Wilcox (Oracle)
2021-06-23 9:54 ` Christoph Hellwig
2021-06-24 23:50 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 39/46] mm/lru: Convert __pagevec_lru_add_fn to take a folio Matthew Wilcox (Oracle)
2021-06-23 9:55 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 40/46] mm/lru: Add folio_add_lru() Matthew Wilcox (Oracle)
2021-06-23 9:56 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 41/46] mm/page_alloc: Add folio allocation functions Matthew Wilcox (Oracle)
2021-06-23 9:58 ` Christoph Hellwig
2021-06-25 1:06 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 42/46] mm/filemap: Add filemap_alloc_folio Matthew Wilcox (Oracle)
2021-06-23 9:59 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 43/46] mm/filemap: Add filemap_add_folio Matthew Wilcox (Oracle)
2021-06-23 11:30 ` Christoph Hellwig
2021-06-25 1:57 ` Matthew Wilcox
2021-06-22 12:15 ` [PATCH v2 44/46] mm/filemap: Convert mapping_get_entry to return a folio Matthew Wilcox (Oracle)
2021-06-23 11:32 ` Christoph Hellwig
2021-06-25 3:29 ` Matthew Wilcox
2021-06-28 6:07 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 45/46] mm/filemap: Add filemap_get_folio Matthew Wilcox (Oracle)
2021-06-23 11:39 ` Christoph Hellwig
2021-06-22 12:15 ` [PATCH v2 46/46] mm/filemap: Add FGP_STABLE Matthew Wilcox (Oracle)
2021-06-23 11:43 ` Christoph Hellwig
2021-06-23 12:15 ` Matthew Wilcox
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210622121551.3398730-4-willy@infradead.org \
--to=willy@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).