Commit 1c8f4220 authored by Souptick Joarder's avatar Souptick Joarder Committed by Linus Torvalds
Browse files

mm: change return type to vm_fault_t 

The plan for these patches is to introduce the typedef, initially just
as documentation ("These functions should return a VM_FAULT_ status").
We'll trickle the patches to individual drivers/filesystems in through
the maintainers, as far as possible.  Then we'll change the typedef to
an unsigned int and break the compilation of any unconverted
drivers/filesystems.

vmf_insert_page(), vmf_insert_mixed() and vmf_insert_pfn() are three
newly added functions.  The various drivers/filesystems where return
value of fault(), huge_fault(), page_mkwrite() and pfn_mkwrite() get
converted, will need them.  These functions will return correct
VM_FAULT_ code based on err value.

We've had bugs before where drivers returned -EFOO.  And we have this
silly inefficiency where vm_insert_xxx() return an errno which (afaict)
every driver then converts into a VM_FAULT code.  In many cases drivers
failed to return correct VM_FAULT code value despite of vm_insert_xxx()
fails.  We have indentified and clean up all those existing bugs and
silly inefficiencies in driver/filesystems by adding these three new
inline wrappers.  As mentioned above, we will trickle those patches to
individual drivers/filesystems in through maintainers after these three
wrapper functions are merged.

Eventually we can convert vm_insert_xxx() into vmf_insert_xxx() and
remove these inline wrappers, but these are a good intermediate step.

Link: http://lkml.kernel.org/r/20180310162351.GA7422@jordon-HP-15-Notebook-PC


Signed-off-by: default avatarSouptick Joarder <jrdr.linux@gmail.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d46078b2

include/linux/mm.h

+43 −4
Original line number Diff line number Diff line
@@ -386,18 +386,19 @@ struct vm_operations_struct { 
	void (*close)(struct vm_area_struct * area);

	int (*split)(struct vm_area_struct * area, unsigned long addr);

	int (*mremap)(struct vm_area_struct * area);

	int (*fault)(struct vm_fault *vmf);

	int (*huge_fault)(struct vm_fault *vmf, enum page_entry_size pe_size);

	vm_fault_t (*fault)(struct vm_fault *vmf);

	vm_fault_t (*huge_fault)(struct vm_fault *vmf,

			enum page_entry_size pe_size);

	void (*map_pages)(struct vm_fault *vmf,

			pgoff_t start_pgoff, pgoff_t end_pgoff);

	unsigned long (*pagesize)(struct vm_area_struct * area);



	/* notification that a previously read-only page is about to become

	 * writable, if an error is returned it will cause a SIGBUS */

	int (*page_mkwrite)(struct vm_fault *vmf);

	vm_fault_t (*page_mkwrite)(struct vm_fault *vmf);



	/* same as page_mkwrite when using VM_PFNMAP|VM_MIXEDMAP */

	int (*pfn_mkwrite)(struct vm_fault *vmf);

	vm_fault_t (*pfn_mkwrite)(struct vm_fault *vmf);



	/* called by access_process_vm when get_user_pages() fails, typically

	 * for use by special VMAs that can switch between memory and hardware
@@ -2424,6 +2425,44 @@ int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr, 
			pfn_t pfn);

int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);



static inline vm_fault_t vmf_insert_page(struct vm_area_struct *vma,

				unsigned long addr, struct page *page)

{

	int err = vm_insert_page(vma, addr, page);



	if (err == -ENOMEM)

		return VM_FAULT_OOM;

	if (err < 0 && err != -EBUSY)

		return VM_FAULT_SIGBUS;



	return VM_FAULT_NOPAGE;

}



static inline vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma,

				unsigned long addr, pfn_t pfn)

{

	int err = vm_insert_mixed(vma, addr, pfn);



	if (err == -ENOMEM)

		return VM_FAULT_OOM;

	if (err < 0 && err != -EBUSY)

		return VM_FAULT_SIGBUS;



	return VM_FAULT_NOPAGE;

}



static inline vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma,

			unsigned long addr, unsigned long pfn)

{

	int err = vm_insert_pfn(vma, addr, pfn);



	if (err == -ENOMEM)

		return VM_FAULT_OOM;

	if (err < 0 && err != -EBUSY)

		return VM_FAULT_SIGBUS;



	return VM_FAULT_NOPAGE;

}



struct page *follow_page_mask(struct vm_area_struct *vma,

			      unsigned long address, unsigned int foll_flags,

include/linux/mm_types.h

+2 −0
Original line number Diff line number Diff line
@@ -22,6 +22,8 @@ 
#endif

#define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))



typedef int vm_fault_t;



struct address_space;

struct mem_cgroup;

struct hmm;

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