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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v9 45/96] mm: Add kmap_local_folio
Date: Wed,  5 May 2021 16:05:37 +0100	[thread overview]
Message-ID: <20210505150628.111735-46-willy@infradead.org> (raw)
In-Reply-To: <20210505150628.111735-1-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..39cdcfdbc23a 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 = nth_page(&folio->page, 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 b06eeeaee975..b01deb45d265 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


  parent reply	other threads:[~2021-05-05 16:04 UTC|newest]

Thread overview: 108+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-05 15:04 [PATCH v9 00/96] Memory folios Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 01/96] mm: Optimise nth_page for contiguous memmap Matthew Wilcox (Oracle)
2021-05-05 17:24   ` Vlastimil Babka
2021-05-05 15:04 ` [PATCH v9 02/96] mm: Make __dump_page static Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 03/96] mm/debug: Factor PagePoisoned out of __dump_page Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 04/96] mm/page_owner: Constify dump_page_owner Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 05/96] mm: Make compound_head const-preserving Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 06/96] mm: Constify get_pfnblock_flags_mask and get_pfnblock_migratetype Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 07/96] mm: Constify page_count and page_ref_count Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 08/96] mm: Fix struct page layout on 32-bit systems Matthew Wilcox (Oracle)
2021-05-05 17:33   ` Vlastimil Babka
2021-05-05 15:05 ` [PATCH v9 09/96] mm: Introduce struct folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 10/96] mm: Add folio_pgdat and folio_zone Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 11/96] mm/vmstat: Add functions to account folio statistics Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 12/96] mm/debug: Add VM_BUG_ON_FOLIO and VM_WARN_ON_ONCE_FOLIO Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 13/96] mm: Add folio reference count functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 14/96] mm: Add folio_put Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 15/96] mm: Add folio_get Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 16/96] mm: Add folio flag manipulation functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 17/96] mm: Add folio_young() and folio_idle() Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 18/96] mm: Handle per-folio private data Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 19/96] mm/filemap: Add folio_index, folio_file_page and folio_contains Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 20/96] mm/filemap: Add folio_next_index Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 21/96] mm/filemap: Add folio_offset and folio_file_offset Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 22/96] mm/util: Add folio_mapping and folio_file_mapping Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 23/96] mm: Add folio_mapcount Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 24/96] mm/memcg: Add folio wrappers for various functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 25/96] mm/filemap: Add folio_unlock Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 26/96] mm/filemap: Add folio_lock Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 27/96] mm/filemap: Add folio_lock_killable Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 28/96] mm/filemap: Add __folio_lock_async Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 29/96] mm/filemap: Add __folio_lock_or_retry Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 30/96] mm/filemap: Add folio_wait_locked Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 31/96] mm/swap: Add folio_rotate_reclaimable Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 32/96] mm/filemap: Add folio_end_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 33/96] mm/writeback: Add folio_wait_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 34/96] mm/writeback: Add folio_wait_stable Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 35/96] mm/filemap: Add folio_wait_bit Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 36/96] mm/filemap: Add folio_wake_bit Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 37/96] mm/filemap: Convert page wait queues to be folios Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 38/96] mm/filemap: Add folio private_2 functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 39/96] fs/netfs: Add folio fscache functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 40/96] mm: Add folio_mapped Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 41/96] mm/workingset: Convert workingset_activation to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 42/96] mm/swap: Add folio_activate Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 43/96] mm/swap: Add folio_mark_accessed Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 44/96] mm/rmap: Add folio_mkclean Matthew Wilcox (Oracle)
2021-05-05 15:05 ` Matthew Wilcox (Oracle) [this message]
2021-05-05 15:05 ` [PATCH v9 46/96] mm: Add flush_dcache_folio Matthew Wilcox (Oracle)
2021-05-05 23:35   ` kernel test robot
2021-05-06  2:33     ` Matthew Wilcox
2021-05-05 15:05 ` [PATCH v9 47/96] mm: Add arch_make_folio_accessible Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 48/96] mm/memcg: Remove 'page' parameter to mem_cgroup_charge_statistics Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 49/96] mm/memcg: Use the node id in mem_cgroup_update_tree Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 50/96] mm/memcg: Convert commit_charge to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 51/96] mm/memcg: Add folio_charge_cgroup Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 52/96] mm/memcg: Add folio_uncharge_cgroup Matthew Wilcox (Oracle)
2021-05-05 20:24   ` kernel test robot
2021-05-05 15:05 ` [PATCH v9 53/96] mm/memcg: Convert mem_cgroup_track_foreign_dirty_slowpath to folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 54/96] mm/writeback: Rename __add_wb_stat to wb_stat_mod Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 55/96] flex_proportions: Allow N events instead of 1 Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 56/96] mm/writeback: Change __wb_writeout_inc to __wb_writeout_add Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 57/96] mm/writeback: Convert test_clear_page_writeback to __folio_end_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 58/96] mm/writeback: Add folio_start_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 59/96] mm/writeback: Add folio_mark_dirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 60/96] mm/writeback: Use __set_page_dirty in __set_page_dirty_nobuffers Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 61/96] mm/writeback: Add __folio_mark_dirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 62/96] mm/writeback: Add filemap_dirty_folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 63/96] mm/writeback: Add folio_account_cleaned Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 64/96] mm/writeback: Add folio_cancel_dirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 65/96] mm/writeback: Add folio_clear_dirty_for_io Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 66/96] mm/writeback: Add folio_account_redirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 67/96] mm/writeback: Add folio_redirty_for_writepage Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 68/96] mm/filemap: Add i_blocks_per_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 69/96] mm/filemap: Add folio_mkwrite_check_truncate Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 70/96] mm/filemap: Add readahead_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 71/96] block: Add bio_add_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 72/96] block: Add bio_for_each_folio_all Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 73/96] mm/lru: Add folio_lru and folio_is_file_lru Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 74/96] mm/workingset: Convert workingset_refault to take a folio Matthew Wilcox (Oracle)
2021-05-05 20:17   ` kernel test robot
2021-05-05 20:57     ` Matthew Wilcox
2021-05-05 15:06 ` [PATCH v9 75/96] mm/lru: Add folio_add_lru Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 76/96] mm/page_alloc: Add __alloc_folio, __alloc_folio_node and alloc_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 77/96] mm/filemap: Add filemap_alloc_folio Matthew Wilcox (Oracle)
2021-05-06  0:00   ` kernel test robot
2021-05-06  2:28     ` Matthew Wilcox
2021-05-05 15:06 ` [PATCH v9 78/96] mm/filemap: Add folio_add_to_page_cache Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 79/96] mm/filemap: Convert mapping_get_entry to return a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 80/96] mm/filemap: Add filemap_get_folio and find_get_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 81/96] mm/filemap: Add filemap_get_stable_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 82/96] iomap: Convert to_iomap_page to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 83/96] iomap: Convert iomap_page_create " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 84/96] iomap: Convert iomap_page_release " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 85/96] iomap: Convert iomap_releasepage to use " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 86/96] iomap: Convert iomap_invalidatepage " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 87/96] iomap: Pass the iomap_page into iomap_set_range_uptodate Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 88/96] iomap: Use folio offsets instead of page offsets Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 89/96] iomap: Convert bio completions to use folios Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 90/96] iomap: Convert readahead and readpage to use a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 91/96] iomap: Convert iomap_page_mkwrite " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 92/96] iomap: Convert iomap_write_begin and iomap_write_end to folios Matthew Wilcox (Oracle)
2021-05-05 21:36   ` kernel test robot
2021-05-05 22:10     ` Matthew Wilcox
2021-05-05 15:06 ` [PATCH v9 93/96] iomap: Convert iomap_read_inline_data to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 94/96] iomap: Convert iomap_write_end_inline " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 95/96] iomap: Convert iomap_add_to_ioend " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 96/96] iomap: Convert iomap_do_writepage to use " Matthew Wilcox (Oracle)

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