[PATCH v2 07/18] fsdax: Update dax_insert_entry() calling convention to return an error

Dan Williams
2022-09-16T03:36:25Z

In preparation for teaching dax_insert_entry() to take live @pgmap
references, enable it to return errors. Given the observation that all
callers overwrite the passed in entry with the return value, just update
@entry in place and convert the return code to a vm_fault_t status.

Cc: Matthew Wilcox <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
fs/dax.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 616bac4b7df3..8382aab0d2f7 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -887,14 +887,15 @@ static bool dax_fault_is_cow(const struct iomap_iter *iter)
* already in the tree, we will skip the insertion and just dirty the PMD as
* appropriate.
*/
-static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
- const struct iomap_iter *iter, void *entry, pfn_t pfn,
- unsigned long flags)
+static vm_fault_t dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
+ const struct iomap_iter *iter, void **pentry,
+ pfn_t pfn, unsigned long flags)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
void *new_entry = dax_make_entry(pfn, flags);
bool dirty = !dax_fault_is_synchronous(iter, vmf->vma);
bool cow = dax_fault_is_cow(iter);
+ void *entry = *pentry;

if (dirty)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
@@ -940,7 +941,8 @@ static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
xas_set_mark(xas, PAGECACHE_TAG_TOWRITE);

xas_unlock_irq(xas);
- return entry;
+ *pentry = entry;
+ return 0;
}

static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
@@ -1188,9 +1190,12 @@ static vm_fault_t dax_load_hole(struct xa_state *xas, struct vm_fault *vmf,
pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr));
vm_fault_t ret;

- *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, DAX_ZERO_PAGE);
+ ret = dax_insert_entry(xas, vmf, iter, entry, pfn, DAX_ZERO_PAGE);
+ if (ret)
+ goto out;

ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
+out:
trace_dax_load_hole(inode, vmf, ret);
return ret;
}
@@ -1207,6 +1212,7 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
struct page *zero_page;
spinlock_t *ptl;
pmd_t pmd_entry;
+ vm_fault_t ret;
pfn_t pfn;

zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);
@@ -1215,8 +1221,10 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, struct vm_fault *vmf,
goto fallback;

pfn = page_to_pfn_t(zero_page);
- *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn,
- DAX_PMD | DAX_ZERO_PAGE);
+ ret = dax_insert_entry(xas, vmf, iter, entry, pfn,
+ DAX_PMD | DAX_ZERO_PAGE);
+ if (ret)
+ return ret;

if (arch_needs_pgtable_deposit()) {
pgtable = pte_alloc_one(vma->vm_mm);
@@ -1568,6 +1576,7 @@ 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;
+ vm_fault_t ret;
int err = 0;
pfn_t pfn;
void *kaddr;
@@ -1592,7 +1601,9 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf,
if (err)
return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);

- *entry = dax_insert_entry(xas, vmf, iter, *entry, pfn, entry_flags);
+ ret = dax_insert_entry(xas, vmf, iter, entry, pfn, entry_flags);
+ if (ret)
+ return ret;

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