The patch titled
Subject: mm: add memcpy_from_file_folio()
has been added to the -mm mm-unstable branch. Its filename is
mm-add-memcpy_from_file_folio.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-memcpy_from_file_folio.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: add memcpy_from_file_folio()
Date: Thu, 26 Jan 2023 20:15:52 +0000
This is the equivalent of memcpy_from_page(). It differs in that it takes
the position in a file instead of offset in a folio, it accepts the total
number of bytes to be copied (instead of the number of bytes to be copied
from this folio) and it returns how many bytes were copied from the folio,
rather than making the caller calculate that and then checking if the
caller got it right.
Link: https://lkml.kernel.org/r/20230126201552.1681588-1-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: "Fabio M. De Francesco" <fmdefrancesco@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/highmem.h | 29 +++++++++++++++++++++++++++++
include/linux/page-flags.h | 1 +
2 files changed, 30 insertions(+)
--- a/include/linux/highmem.h~mm-add-memcpy_from_file_folio
+++ a/include/linux/highmem.h
@@ -414,6 +414,35 @@ static inline void memzero_page(struct p
}
/**
+ * memcpy_from_file_folio - Copy some bytes from a file folio.
+ * @to: The destination buffer.
+ * @folio: The folio to copy from.
+ * @pos: The position in the file.
+ * @len: The maximum number of bytes to copy.
+ *
+ * Copy up to @len bytes from this folio. This may be limited by PAGE_SIZE
+ * if the folio comes from HIGHMEM, and by the size of the folio.
+ *
+ * Return: The number of bytes copied from the folio.
+ */
+static inline size_t memcpy_from_file_folio(char *to, struct folio *folio,
+ loff_t pos, size_t len)
+{
+ size_t offset = offset_in_folio(folio, pos);
+ char *from = kmap_local_folio(folio, offset);
+
+ if (folio_test_highmem(folio))
+ len = min(len, PAGE_SIZE - offset);
+ else
+ len = min(len, folio_size(folio) - offset);
+
+ memcpy(to, from, len);
+ kunmap_local(from);
+
+ return len;
+}
+
+/**
* folio_zero_segments() - Zero two byte ranges in a folio.
* @folio: The folio to write to.
* @start1: The first byte to zero.
--- a/include/linux/page-flags.h~mm-add-memcpy_from_file_folio
+++ a/include/linux/page-flags.h
@@ -531,6 +531,7 @@ PAGEFLAG(Readahead, readahead, PF_NO_COM
* available at this point.
*/
#define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
+#define folio_test_highmem(__f) is_highmem_idx(folio_zonenum(__f))
#else
PAGEFLAG_FALSE(HighMem, highmem)
#endif
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-remove-folio_pincount_ptr-and-head_compound_pincount.patch
mm-convert-head_subpages_mapcount-into-folio_nr_pages_mapped.patch
doc-clarify-refcount-section-by-referring-to-folios-pages.patch
mm-convert-total_compound_mapcount-to-folio_total_mapcount.patch
mm-convert-page_remove_rmap-to-use-a-folio-internally.patch
mm-convert-page_add_anon_rmap-to-use-a-folio-internally.patch
mm-convert-page_add_file_rmap-to-use-a-folio-internally.patch
mm-add-folio_add_new_anon_rmap.patch
mm-add-folio_add_new_anon_rmap-fix-2.patch
page_alloc-use-folio-fields-directly.patch
mm-use-a-folio-in-hugepage_add_anon_rmap-and-hugepage_add_new_anon_rmap.patch
mm-use-entire_mapcount-in-__page_dup_rmap.patch
mm-debug-remove-call-to-head_compound_mapcount.patch
hugetlb-remove-uses-of-folio_mapcount_ptr.patch
mm-convert-page_mapcount-to-use-folio_entire_mapcount.patch
mm-remove-head_compound_mapcount-and-_ptr-functions.patch
mm-reimplement-compound_order.patch
mm-reimplement-compound_nr.patch
mm-reimplement-compound_nr-fix.patch
mm-convert-set_compound_page_dtor-and-set_compound_order-to-folios.patch
mm-convert-is_transparent_hugepage-to-use-a-folio.patch
mm-convert-destroy_large_folio-to-use-folio_dtor.patch
hugetlb-remove-uses-of-compound_dtor-and-compound_nr.patch
mm-remove-first-tail-page-members-from-struct-page.patch
doc-correct-struct-folio-kernel-doc.patch
mm-move-page-deferred_list-to-folio-_deferred_list.patch
mm-huge_memory-remove-page_deferred_list.patch
mm-huge_memory-convert-get_deferred_split_queue-to-take-a-folio.patch
mm-convert-deferred_split_huge_page-to-deferred_split_folio.patch
shmem-convert-shmem_write_end-to-use-a-folio.patch
mm-add-vma_alloc_zeroed_movable_folio.patch
mm-convert-do_anonymous_page-to-use-a-folio.patch
mm-convert-wp_page_copy-to-use-folios.patch
mm-use-a-folio-in-copy_pte_range.patch
mm-use-a-folio-in-copy_present_pte.patch
mm-fs-convert-inode_attach_wb-to-take-a-folio.patch
mm-convert-mem_cgroup_css_from_page-to-mem_cgroup_css_from_folio.patch
mm-remove-page_evictable.patch
mm-remove-mlock_vma_page.patch
mm-remove-munlock_vma_page.patch
mm-clean-up-mlock_page-munlock_page-references-in-comments.patch
rmap-add-folio-parameter-to-__page_set_anon_rmap.patch
filemap-convert-filemap_map_pmd-to-take-a-folio.patch
filemap-convert-filemap_range_has_page-to-use-a-folio.patch
readahead-convert-readahead_expand-to-use-a-folio.patch
mm-add-memcpy_from_file_folio.patch
