From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
dax_iomap_cow copies a page before presenting for mmap.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
fs/dax.c | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)
diff --git a/fs/dax.c b/fs/dax.c
index e254535dd830..21ee3df6f02c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1269,6 +1269,33 @@ static bool dax_fault_is_synchronous(unsigned long flags,
&& (iomap->flags & IOMAP_F_DIRTY);
}
+static int dax_iomap_cow(struct iomap *iomap, loff_t pos, pfn_t *pfn)
+{
+ void *daddr;
+ pgoff_t pgoff;
+ long rc;
+ int id;
+ sector_t sector;
+
+ pos = round_down(pos, PAGE_SIZE);
+
+ sector = round_down(iomap->addr + iomap->offset - pos, PAGE_SIZE) >> 9;
+ rc = bdev_dax_pgoff(iomap->bdev, sector, PAGE_SIZE, &pgoff);
+ if (rc)
+ return rc;
+
+ id = dax_read_lock();
+ rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &daddr, pfn);
+ if (rc < 0)
+ goto out;
+
+ dax_to_dax_copy(iomap, pos, daddr, PAGE_SIZE);
+
+out:
+ dax_read_unlock(id);
+ return rc;
+}
+
static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
int *iomap_errp, const struct iomap_ops *ops)
{
@@ -1372,7 +1399,11 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
major = VM_FAULT_MAJOR;
}
- error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
+
+ if (iomap.flags & IOMAP_F_COW)
+ error = dax_iomap_cow(&iomap, pos, &pfn);
+ else
+ error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
if (error < 0)
goto error_finish_iomap;
--
2.16.4
