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authorMatthew Wilcox (Oracle) <willy@infradead.org>2023-11-07 21:26:40 +0000
committerAndrew Morton <akpm@linux-foundation.org>2023-12-10 16:51:36 -0800
commita4fc4a0c45f2617c3aa8b693739de264e0c09909 (patch)
treebca2d3828d6b72fd85c15535a3e8b5e265f020d7 /include
parent600bca580579d8d8454cc8fe3290e2f8b9c01884 (diff)
mm: add folio_zero_tail() and use it in ext4
Patch series "Add folio_zero_tail() and folio_fill_tail()". I'm trying to make it easier for filesystems with tailpacking / stuffing / inline data to use folios. The primary function here is folio_fill_tail(). You give it a pointer to memory where the data currently is, and it takes care of copying it into the folio at that offset. That works for gfs2 & iomap. Then There's Ext4. Rather than gin up some kind of specialist "Here's a two pointers to two blocks of memory" routine, just let it do its current thing, and let it call folio_zero_tail(), which is also called by folio_fill_tail(). Other filesystems can be converted later; these ones seemed like good examples as they're already partly or completely converted to folios. This patch (of 3): Instead of unmapping the folio after copying the data to it, then mapping it again to zero the tail, provide folio_zero_tail() to zero the tail of an already-mapped folio. [akpm@linux-foundation.org: fix kerneldoc argument ordering] Link: https://lkml.kernel.org/r/20231107212643.3490372-1-willy@infradead.org Link: https://lkml.kernel.org/r/20231107212643.3490372-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com> Cc: Darrick J. Wong <djwong@kernel.org> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/highmem.h38
1 files changed, 38 insertions, 0 deletions
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index be20cff4ba73..5ebd5e4dfbf8 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -484,6 +484,44 @@ static inline void memcpy_to_folio(struct folio *folio, size_t offset,
}
/**
+ * folio_zero_tail - Zero the tail of a folio.
+ * @folio: The folio to zero.
+ * @offset: The byte offset in the folio to start zeroing at.
+ * @kaddr: The address the folio is currently mapped to.
+ *
+ * If you have already used kmap_local_folio() to map a folio, written
+ * some data to it and now need to zero the end of the folio (and flush
+ * the dcache), you can use this function. If you do not have the
+ * folio kmapped (eg the folio has been partially populated by DMA),
+ * use folio_zero_range() or folio_zero_segment() instead.
+ *
+ * Return: An address which can be passed to kunmap_local().
+ */
+static inline __must_check void *folio_zero_tail(struct folio *folio,
+ size_t offset, void *kaddr)
+{
+ size_t len = folio_size(folio) - offset;
+
+ if (folio_test_highmem(folio)) {
+ size_t max = PAGE_SIZE - offset_in_page(offset);
+
+ while (len > max) {
+ memset(kaddr, 0, max);
+ kunmap_local(kaddr);
+ len -= max;
+ offset += max;
+ max = PAGE_SIZE;
+ kaddr = kmap_local_folio(folio, offset);
+ }
+ }
+
+ memset(kaddr, 0, len);
+ flush_dcache_folio(folio);
+
+ return kaddr;
+}
+
+/**
* memcpy_from_file_folio - Copy some bytes from a file folio.
* @to: The destination buffer.
* @folio: The folio to copy from.