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Subject[PATCH 14/23] thp, mm: naive support of thp in generic_perform_write
Date
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

For now we still write/read at most PAGE_CACHE_SIZE bytes a time.

This implementation doesn't cover address spaces with backing storage.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/filemap.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index b17ebb9..066bbff 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2382,6 +2382,7 @@ static ssize_t generic_perform_write(struct file *file,
unsigned long bytes; /* Bytes to write to page */
size_t copied; /* Bytes copied from user */
void *fsdata;
+ int subpage_nr = 0;

offset = (pos & (PAGE_CACHE_SIZE - 1));
bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
@@ -2411,8 +2412,14 @@ again:
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);

+ if (PageTransHuge(page)) {
+ off_t huge_offset = pos & ~HPAGE_PMD_MASK;
+ subpage_nr = huge_offset >> PAGE_CACHE_SHIFT;
+ }
+
pagefault_disable();
- copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
+ copied = iov_iter_copy_from_user_atomic(page + subpage_nr, i,
+ offset, bytes);
pagefault_enable();
flush_dcache_page(page);

--
1.8.3.2


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