linux-ext4 - [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap

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Message-Id: <20161012225022.15507-13-ross.zwisler@linux.intel.com>
Date:   Wed, 12 Oct 2016 16:50:17 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org,
        linux-xfs@...r.kernel.org
Subject: [PATCH v6 12/17] dax: dax_iomap_fault() needs to call iomap_end()

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@...ux.intel.com>
Suggested-by: Jan Kara <jack@...e.cz>
Reviewed-by: Jan Kara <jack@...e.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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