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fsdax: zero the edges if source is HOLE or UNWRITTEN

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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: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Shiyang Ruan 2022-12-01 15:28:53 +00:00 committed by Andrew Morton
parent f80e166888
commit 708dfad2eb
1 changed files with 49 additions and 30 deletions
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79
fs/dax.c
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@ -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)
@ -1101,35 +1102,50 @@ 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;
ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
if (ret)
return ret;
if (!zero_edge) {
ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL);
if (ret)
return ret;
}
if (copy_all) {
ret = copy_mc_to_kernel(daddr, saddr, length);
return ret ? -EIO : 0;
if (zero_edge)
memset(daddr, 0, size);
else
ret = copy_mc_to_kernel(daddr, saddr, length);
goto out;
}
/* Copy the head part of the range */
if (head_off) {
ret = copy_mc_to_kernel(daddr, saddr, head_off);
if (ret)
return -EIO;
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 */
@ -1137,12 +1153,19 @@ static int dax_iomap_cow_copy(loff_t pos, uint64_t length, size_t align_size,
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 (ret)
return -EIO;
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,
kaddr);
if (ret < 0)
return ret;
dax_flush(iomap->dax_dev, kaddr, PAGE_SIZE);
} else
if (iomap->flags & IOMAP_F_SHARED)
ret = dax_iomap_copy_around(pos, size, PAGE_SIZE, srcmap,
kaddr);
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);
}