dax, iomap: Add support for synchronous faults
Add a flag to iomap interface informing the caller that inode needs
fdstasync(2) for returned extent to become persistent and use it in DAX
fault code so that we don't map such extents into page tables
immediately. Instead we propagate the information that fdatasync(2) is
necessary from dax_iomap_fault() with a new VM_FAULT_NEEDDSYNC flag.
Filesystem fault handler is then responsible for calling fdatasync(2)
and inserting pfn into page tables.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/fs/dax.c b/fs/dax.c
index efc210f..bb9ff90 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1091,6 +1091,7 @@
unsigned flags = IOMAP_FAULT;
int error, major = 0;
bool write = vmf->flags & FAULT_FLAG_WRITE;
+ bool sync;
int vmf_ret = 0;
void *entry;
pfn_t pfn;
@@ -1169,6 +1170,8 @@
goto finish_iomap;
}
+ sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY);
+
switch (iomap.type) {
case IOMAP_MAPPED:
if (iomap.flags & IOMAP_F_NEW) {
@@ -1182,12 +1185,27 @@
entry = dax_insert_mapping_entry(mapping, vmf, entry,
dax_iomap_sector(&iomap, pos),
- 0, write);
+ 0, write && !sync);
if (IS_ERR(entry)) {
error = PTR_ERR(entry);
goto error_finish_iomap;
}
+ /*
+ * If we are doing synchronous page fault and inode needs fsync,
+ * we can insert PTE into page tables only after that happens.
+ * Skip insertion for now and return the pfn so that caller can
+ * insert it after fsync is done.
+ */
+ if (sync) {
+ if (WARN_ON_ONCE(!pfnp)) {
+ error = -EIO;
+ goto error_finish_iomap;
+ }
+ *pfnp = pfn;
+ vmf_ret = VM_FAULT_NEEDDSYNC | major;
+ goto finish_iomap;
+ }
trace_dax_insert_mapping(inode, vmf, entry);
if (write)
error = vm_insert_mixed_mkwrite(vma, vaddr, pfn);
@@ -1287,6 +1305,7 @@
struct address_space *mapping = vma->vm_file->f_mapping;
unsigned long pmd_addr = vmf->address & PMD_MASK;
bool write = vmf->flags & FAULT_FLAG_WRITE;
+ bool sync;
unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
struct inode *inode = mapping->host;
int result = VM_FAULT_FALLBACK;
@@ -1371,6 +1390,8 @@
if (iomap.offset + iomap.length < pos + PMD_SIZE)
goto finish_iomap;
+ sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY);
+
switch (iomap.type) {
case IOMAP_MAPPED:
error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
@@ -1379,10 +1400,24 @@
entry = dax_insert_mapping_entry(mapping, vmf, entry,
dax_iomap_sector(&iomap, pos),
- RADIX_DAX_PMD, write);
+ RADIX_DAX_PMD, write && !sync);
if (IS_ERR(entry))
goto finish_iomap;
+ /*
+ * If we are doing synchronous page fault and inode needs fsync,
+ * we can insert PMD into page tables only after that happens.
+ * Skip insertion for now and return the pfn so that caller can
+ * insert it after fsync is done.
+ */
+ if (sync) {
+ if (WARN_ON_ONCE(!pfnp))
+ goto finish_iomap;
+ *pfnp = pfn;
+ result = VM_FAULT_NEEDDSYNC;
+ goto finish_iomap;
+ }
+
trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
write);