Commit 708dfad2 authored by Shiyang Ruan's avatar Shiyang Ruan Committed by Andrew Morton
Browse files

fsdax: zero the edges if source is HOLE or UNWRITTEN 

If srcmap contains invalid data, such as HOLE and UNWRITTEN, the dest page
should be zeroed.  Otherwise, since it's a pmem, old data may remains on
the dest page, the result of CoW will be incorrect.

The function name is also not easy to understand, rename it to
"dax_iomap_copy_around()", which means it copies data around the range.

[akpm@linux-foundation.org: update dax_iomap_copy_around() kerneldoc, per Darrick]
Link: https://lkml.kernel.org/r/1669973145-318-1-git-send-email-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/1669908538-55-4-git-send-email-ruansy.fnst@fujitsu.com


Signed-off-by: default avatarShiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarAllison Henderson <allison.henderson@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f80e1668

fs/dax.c

+49 −30
Original line number Diff line number Diff line
@@ -1092,7 +1092,8 @@ static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos, 
}



/**

 * dax_iomap_cow_copy - Copy the data from source to destination before write

 * dax_iomap_copy_around - Prepare for an unaligned write to a shared/cow page

 * by copying the data before and after the range to be written.

 * @pos:	address to do copy from.

 * @length:	size of copy operation.

 * @align_size:	aligned w.r.t align_size (either PMD_SIZE or PAGE_SIZE)
@@ -1101,48 +1102,70 @@ static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos, 
 *

 * This can be called from two places. Either during DAX write fault (page

 * aligned), to copy the length size data to daddr. Or, while doing normal DAX

 * write operation, dax_iomap_actor() might call this to do the copy of either

 * write operation, dax_iomap_iter() might call this to do the copy of either

 * start or end unaligned address. In the latter case the rest of the copy of

 * aligned ranges is taken care by dax_iomap_actor() itself.

 * aligned ranges is taken care by dax_iomap_iter() itself.

 * If the srcmap contains invalid data, such as HOLE and UNWRITTEN, zero the

 * area to make sure no old data remains.

 */

static int dax_iomap_cow_copy(loff_t pos, uint64_t length, size_t align_size,

static int dax_iomap_copy_around(loff_t pos, uint64_t length, size_t align_size,

		const struct iomap *srcmap, void *daddr)

{

	loff_t head_off = pos & (align_size - 1);

	size_t size = ALIGN(head_off + length, align_size);

	loff_t end = pos + length;

	loff_t pg_end = round_up(end, align_size);

	/* copy_all is usually in page fault case */

	bool copy_all = head_off == 0 && end == pg_end;

	/* zero the edges if srcmap is a HOLE or IOMAP_UNWRITTEN */

	bool zero_edge = srcmap->flags & IOMAP_F_SHARED ||

			 srcmap->type == IOMAP_UNWRITTEN;

	void *saddr = 0;

	int ret = 0;



	if (!zero_edge) {

		ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);

		if (ret)

			return ret;

	}



	if (copy_all) {

		if (zero_edge)

			memset(daddr, 0, size);

		else

			ret = copy_mc_to_kernel(daddr, saddr, length);

		return ret ? -EIO : 0;

		goto out;

	}



	/* Copy the head part of the range */

	if (head_off) {

		if (zero_edge)

			memset(daddr, 0, head_off);

		else {

			ret = copy_mc_to_kernel(daddr, saddr, head_off);

			if (ret)

				return -EIO;

		}

	}



	/* Copy the tail part of the range */

	if (end < pg_end) {

		loff_t tail_off = head_off + length;

		loff_t tail_len = pg_end - end;



		ret = copy_mc_to_kernel(daddr + tail_off, saddr + tail_off,

					tail_len);

		if (zero_edge)

			memset(daddr + tail_off, 0, tail_len);

		else {

			ret = copy_mc_to_kernel(daddr + tail_off,

						saddr + tail_off, tail_len);

			if (ret)

				return -EIO;

		}

	return 0;

	}

out:

	if (zero_edge)

		dax_flush(srcmap->dax_dev, daddr, size);

	return ret ? -EIO : 0;

}



/*
@@ -1241,13 +1264,10 @@ static int dax_memzero(struct iomap_iter *iter, loff_t pos, size_t size) 
	if (ret < 0)

		return ret;

	memset(kaddr + offset, 0, size);

	if (srcmap->addr != iomap->addr) {

		ret = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,

	if (iomap->flags & IOMAP_F_SHARED)

		ret = dax_iomap_copy_around(pos, size, PAGE_SIZE, srcmap,

					    kaddr);

		if (ret < 0)

			return ret;

		dax_flush(iomap->dax_dev, kaddr, PAGE_SIZE);

	} else

	else

		dax_flush(iomap->dax_dev, kaddr + offset, size);

	return ret;

}
@@ -1401,8 +1421,8 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi, 
		}



		if (cow) {

			ret = dax_iomap_cow_copy(pos, length, PAGE_SIZE, srcmap,

						 kaddr);

			ret = dax_iomap_copy_around(pos, length, PAGE_SIZE,

						    srcmap, kaddr);

			if (ret)

				break;

		}
@@ -1547,7 +1567,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf, 
		struct xa_state *xas, void **entry, bool pmd)

{

	const struct iomap *iomap = &iter->iomap;

	const struct iomap *srcmap = &iter->srcmap;

	const struct iomap *srcmap = iomap_iter_srcmap(iter);

	size_t size = pmd ? PMD_SIZE : PAGE_SIZE;

	loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT;

	bool write = iter->flags & IOMAP_WRITE;
@@ -1578,9 +1598,8 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf, 


	*entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, entry_flags);



	if (write &&

	    srcmap->type != IOMAP_HOLE && srcmap->addr != iomap->addr) {

		err = dax_iomap_cow_copy(pos, size, size, srcmap, kaddr);

	if (write && iomap->flags & IOMAP_F_SHARED) {

		err = dax_iomap_copy_around(pos, size, size, srcmap, kaddr);

		if (err)

			return dax_fault_return(err);

	}