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authorDave Chinner <dchinner@redhat.com>2015-06-04 09:18:18 +1000
committerDave Chinner <david@fromorbit.com>2015-06-04 09:18:18 +1000
commitce5c5d554dc47a4fb4360c84b72231fea081e7a0 (patch)
tree93915bd75b2061c36dfbffd10a8efd22e0d7282b /fs/dax.c
parente842f2903908934187af7232fb5b21da527d1757 (diff)
dax: expose __dax_fault for filesystems with locking constraints
Some filesystems cannot call dax_fault() directly because they have different locking and/or allocation constraints in the page fault IO path. To handle this, we need to follow the same model as the generic block_page_mkwrite code, where the internals are exposed via __block_page_mkwrite() so that filesystems can wrap the correct locking and operations around the outside. This is loosely based on a patch originally from Matthew Willcox. Unlike the original patch, it does not change ext4 code, error returns or unwritten extent conversion handling. It also adds a __dax_mkwrite() wrapper for .page_mkwrite implementations to do the right thing, too. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/dax.c')
-rw-r--r--fs/dax.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/fs/dax.c b/fs/dax.c
index 4bb5b7cd5dfd..99b5fbc38992 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -312,7 +312,17 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
return error;
}
-static int do_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+/**
+ * __dax_fault - handle a page fault on a DAX file
+ * @vma: The virtual memory area where the fault occurred
+ * @vmf: The description of the fault
+ * @get_block: The filesystem method used to translate file offsets to blocks
+ *
+ * When a page fault occurs, filesystems may call this helper in their
+ * fault handler for DAX files. __dax_fault() assumes the caller has done all
+ * the necessary locking for the page fault to proceed successfully.
+ */
+int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
get_block_t get_block, dax_iodone_t complete_unwritten)
{
struct file *file = vma->vm_file;
@@ -443,6 +453,7 @@ static int do_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
}
goto out;
}
+EXPORT_SYMBOL(__dax_fault);
/**
* dax_fault - handle a page fault on a DAX file
@@ -463,7 +474,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
sb_start_pagefault(sb);
file_update_time(vma->vm_file);
}
- result = do_dax_fault(vma, vmf, get_block, complete_unwritten);
+ result = __dax_fault(vma, vmf, get_block, complete_unwritten);
if (vmf->flags & FAULT_FLAG_WRITE)
sb_end_pagefault(sb);