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dax: expose __dax_fault for filesystems with locking constraints

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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>
This commit is contained in:
Dave Chinner 2015-06-04 09:18:18 +10:00 committed by Dave Chinner
parent e842f29039
commit ce5c5d554d
2 changed files with 17 additions and 3 deletions
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15
fs/dax.c
View File

@ -312,7 +312,17 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
return error; 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) get_block_t get_block, dax_iodone_t complete_unwritten)
{ {
struct file *file = vma->vm_file; 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; goto out;
} }
EXPORT_SYMBOL(__dax_fault);
/** /**
* dax_fault - handle a page fault on a DAX file * 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); sb_start_pagefault(sb);
file_update_time(vma->vm_file); 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) if (vmf->flags & FAULT_FLAG_WRITE)
sb_end_pagefault(sb); sb_end_pagefault(sb);

5
include/linux/fs.h
View File

@ -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_truncate_page(struct inode *, loff_t from, get_block_t);
int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t, int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,
dax_iodone_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 *); 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)
#define __dax_mkwrite(vma, vmf, gb, iod) __dax_fault(vma, vmf, gb, iod)
#ifdef CONFIG_BLOCK #ifdef CONFIG_BLOCK
typedef void (dio_submit_t)(int rw, struct bio *bio, struct inode *inode, typedef void (dio_submit_t)(int rw, struct bio *bio, struct inode *inode,