In preparation for dax_insert_entry() to start taking page and pgmap
references ensure that page->pgmap is valid by holding the
dax_read_lock() over both dax_direct_access() and dax_insert_entry().
I.e. the code that wants to elevate the reference count of a pgmap page
from 0 -> 1 must ensure that the pgmap is not exiting and will not start
exiting until the proper references have been taken.
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
fs/dax.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 1d4f0072e58d..6990a6e7df9f 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1107,10 +1107,9 @@ static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos,
size_t size, void **kaddr, pfn_t *pfnp)
{
pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
- int id, rc = 0;
long length;
+ int rc = 0;
- id = dax_read_lock();
length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
DAX_ACCESS, kaddr, pfnp);
if (length < 0) {
@@ -1135,7 +1134,6 @@ static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos,
if (!*kaddr)
rc = -EFAULT;
out:
- dax_read_unlock(id);
return rc;
}
@@ -1588,7 +1586,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT;
bool write = iter->flags & IOMAP_WRITE;
unsigned long entry_flags = pmd ? DAX_PMD : 0;
- int err = 0;
+ int err = 0, id;
pfn_t pfn;
void *kaddr;
@@ -1608,11 +1606,15 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS;
}
+ id = dax_read_lock();
err = dax_iomap_direct_access(iomap, pos, size, &kaddr, &pfn);
- if (err)
+ if (err) {
+ dax_read_unlock(id);
return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);
+ }
*entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, entry_flags);
+ dax_read_unlock(id);
if (write &&
srcmap->type != IOMAP_HOLE && srcmap->addr != iomap->addr) {
