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Commit ce5c5d55 authored by Dave Chinner's avatar Dave Chinner Committed by Dave Chinner
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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: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent e842f290

fs/dax.c

+13 −2
Original line number Diff line number Diff line
@@ -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);

include/linux/fs.h

+4 −1
Original line number Diff line number Diff line
@@ -2630,8 +2630,11 @@ int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t); 
int dax_truncate_page(struct inode *, loff_t from, get_block_t);

int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,

		dax_iodone_t);

int __dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,

		dax_iodone_t);

int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);

#define dax_mkwrite(vma, vmf, gb, iod)		dax_fault(vma, vmf, gb, iod)

#define __dax_mkwrite(vma, vmf, gb, iod)	__dax_fault(vma, vmf, gb, iod)



#ifdef CONFIG_BLOCK

typedef void (dio_submit_t)(int rw, struct bio *bio, struct inode *inode,