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[PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end()

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Currently iomap_end() doesn't do anything for DAX page faults for both ext2
and XFS.  ext2_iomap_end() just checks for a write underrun, and
xfs_file_iomap_end() checks to see if it needs to finish a delayed
allocation.  However, in the future iomap_end() calls might be needed to
make sure we have balanced allocations, locks, etc.  So, add calls to
iomap_end() with appropriate error handling to dax_iomap_fault().

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/dax.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 7737954..6edd89b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1165,6 +1165,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct iomap iomap = { 0 };
 	unsigned flags = 0;
 	int error, major = 0;
+	int locked_status = 0;
 	void *entry;
 
 	/*
@@ -1194,7 +1195,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		goto unlock_entry;
 	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 		error = -EIO;		/* fs corruption? */
-		goto unlock_entry;
+		goto finish_iomap;
 	}
 
 	sector = dax_iomap_sector(&iomap, pos);
@@ -1216,13 +1217,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		}
 
 		if (error)
-			goto unlock_entry;
+			goto finish_iomap;
 		if (!radix_tree_exceptional_entry(entry)) {
 			vmf->page = entry;
-			return VM_FAULT_LOCKED;
+			locked_status = VM_FAULT_LOCKED;
+		} else {
+			vmf->entry = entry;
+			locked_status = VM_FAULT_DAX_LOCKED;
 		}
-		vmf->entry = entry;
-		return VM_FAULT_DAX_LOCKED;
+		goto finish_iomap;
 	}
 
 	switch (iomap.type) {
@@ -1237,8 +1240,10 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
-		if (!(vmf->flags & FAULT_FLAG_WRITE))
-			return dax_load_hole(mapping, entry, vmf);
+		if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+			locked_status = dax_load_hole(mapping, entry, vmf);
+			break;
+		}
 		/*FALLTHRU*/
 	default:
 		WARN_ON_ONCE(1);
@@ -1246,14 +1251,30 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		break;
 	}
 
+ finish_iomap:
+	if (ops->iomap_end) {
+		if (error) {
+			/* keep previous error */
+			ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
+					&iomap);
+		} else {
+			error = ops->iomap_end(inode, pos, PAGE_SIZE,
+					PAGE_SIZE, flags, &iomap);
+		}
+	}
  unlock_entry:
-	put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+	if (!locked_status || error)
+		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
 	if (error == -ENOMEM)
 		return VM_FAULT_OOM | major;
 	/* -EBUSY is fine, somebody else faulted on the same PTE */
 	if (error < 0 && error != -EBUSY)
 		return VM_FAULT_SIGBUS | major;
+	if (locked_status) {
+		WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
+		return locked_status;
+	}
 	return VM_FAULT_NOPAGE | major;
 }
 EXPORT_SYMBOL_GPL(dax_iomap_fault);
-- 
2.9.0

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[PATCH v6 00/17] re-enable DAX PMD support Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 13/17] dax: move RADIX_DAX_* defines to dax.h Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 11/17] dax: add dax_iomap_sector() helper function Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 10/17] dax: correct dax iomap code namespace Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in dax.c Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
    Re: [PATCH v6 14/17] dax: move put_(un)locked_mapping_entry() in  dax.c Jan Kara <jack@suse.cz> - 2016-10-13 17:20 +0200
  [PATCH v6 16/17] xfs: use struct iomap based DAX PMD fault path Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 05/17] dax: make 'wait_table' global variable static Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 07/17] dax: consistent variable naming for DAX entries Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 08/17] dax: coordinate locking for offsets in PMD range Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 02/17] ext4: tell DAX the size of allocation holes Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 01/17] ext4: allow DAX writeback for hole punch Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
  [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200
    Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD Jan Kara <jack@suse.cz> - 2016-10-13 17:50 +0200
    Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2016-10-17 08:00 +0200
      Re: [PATCH v6 17/17] dax: remove "depends on BROKEN" from FS_DAX_PMD Jan Kara <jack@suse.cz> - 2016-10-17 11:20 +0200
  [PATCH v6 06/17] dax: remove the last BUG_ON() from fs/dax.c Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-10-13 01:00 +0200

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