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x86/asm/memcpy_mcsafe: Return bytes remaining

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Machine check safe memory copies are currently deployed in the pmem
driver whenever reading from persistent memory media, so that -EIO is
returned rather than triggering a kernel panic. While this protects most
pmem accesses, it is not complete in the filesystem-dax case. When
filesystem-dax is enabled reads may bypass the block layer and the
driver via dax_iomap_actor() and its usage of copy_to_iter().

In preparation for creating a copy_to_iter() variant that can handle
machine checks, teach memcpy_mcsafe() to return the number of bytes
remaining rather than -EFAULT when an exception occurs.

Co-developed-by: Tony Luck <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/152539238119.31796.14318473522414462886.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Dan Williams 2018-05-03 17:06:21 -07:00 • committed by Ingo Molnar
commit 60622d6822
5 changed files with 26 additions and 15 deletions
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3
drivers/nvdimm/claim.c
View file

@ -276,7 +276,8 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
if (rw == READ) {
if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align)))
return -EIO;
return memcpy_mcsafe(buf, nsio->addr + offset, size);
if (memcpy_mcsafe(buf, nsio->addr + offset, size) != 0)
return -EIO;
}
if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) {

6
drivers/nvdimm/pmem.c
View file

@ -101,15 +101,15 @@ static blk_status_t read_pmem(struct page *page, unsigned int off,
void *pmem_addr, unsigned int len)
{
unsigned int chunk;
int rc;
unsigned long rem;
void *mem;
while (len) {
mem = kmap_atomic(page);
chunk = min_t(unsigned int, len, PAGE_SIZE);
rc = memcpy_mcsafe(mem + off, pmem_addr, chunk);
rem = memcpy_mcsafe(mem + off, pmem_addr, chunk);
kunmap_atomic(mem);
if (rc)
if (rem)
return BLK_STS_IOERR;
len -= chunk;
off = 0;