From: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Subject: 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: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 47 +++++++++++++++++++++++++++++++++----
include/linux/mm_types.h | 2 +
2 files changed, 45 insertions(+), 4 deletions(-)
diff -puN include/linux/mm.h~mm-change-return-type-to-vm_fault_t include/linux/mm.h
--- a/include/linux/mm.h~mm-change-return-type-to-vm_fault_t
+++ a/include/linux/mm.h
@@ -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_ar
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,
diff -puN include/linux/mm_types.h~mm-change-return-type-to-vm_fault_t include/linux/mm_types.h
--- a/include/linux/mm_types.h~mm-change-return-type-to-vm_fault_t
+++ a/include/linux/mm_types.h
@@ -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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