dax_copy_edges() is a helper functions performs a copy from one part of the device to another for data not page aligned.
Signed-off-by: Goldwyn Rodrigues <rgold...@suse.com> Signed-off-by: Shiyang Ruan <ruansy.f...@cn.fujitsu.com> --- fs/dax.c | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/fs/dax.c b/fs/dax.c index b012b2db7ba2..ea4e8a434900 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1038,6 +1038,47 @@ static int dax_iomap_direct_access(struct iomap *iomap, loff_t pos, size_t size, return rc; } +/* + * Copies the part of the pages not included in the write, but required for CoW + * because offset/offset+length are not page aligned. + */ +static int dax_copy_edges(loff_t pos, loff_t length, struct iomap *srcmap, + void *daddr, bool pmd) +{ + size_t page_size = pmd ? PMD_SIZE : PAGE_SIZE; + loff_t offset = pos & (page_size - 1); + size_t size = ALIGN(offset + length, page_size); + loff_t end = pos + length; + loff_t pg_end = round_up(end, page_size); + void *saddr = 0; + int ret = 0; + + ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL); + if (ret) + return ret; + /* + * Copy the first part of the page + * Note: we pass offset as length + */ + if (offset) { + if (saddr) + ret = copy_mc_to_kernel(daddr, saddr, offset); + else + memset(daddr, 0, offset); + } + + /* Copy the last part of the range */ + if (end < pg_end) { + if (saddr) + ret = copy_mc_to_kernel(daddr + offset + length, + saddr + offset + length, pg_end - end); + else + memset(daddr + offset + length, 0, pg_end - end); + } + + return ret; +} + /* * The user has performed a load from a hole in the file. Allocating a new * page in the file would cause excessive storage usage for workloads with -- 2.30.0