linux-toradex.git/mm/memory.c, branch v4.20

mm: Fix warning in insert_pfn()

2018-10-31T15:54:17+00:00

In DAX mode a write pagefault can race with write(2) in the following
way:

CPU0                            CPU1
                                write fault for mapped zero page (hole)
dax_iomap_rw()
  iomap_apply()
    xfs_file_iomap_begin()
      - allocates blocks
    dax_iomap_actor()
      invalidate_inode_pages2_range()
        - invalidates radix tree entries in given range
                                dax_iomap_pte_fault()
                                  grab_mapping_entry()
                                    - no entry found, creates empty
                                  ...
                                  xfs_file_iomap_begin()
                                    - finds already allocated block
                                  ...
                                  vmf_insert_mixed_mkwrite()
                                    - WARNs and does nothing because there
                                      is still zero page mapped in PTE
        unmap_mapping_pages()

This race results in WARN_ON from insert_pfn() and is occasionally
triggered by fstest generic/344. Note that the race is otherwise
harmless as before write(2) on CPU0 is finished, we will invalidate page
tables properly and thus user of mmap will see modified data from
write(2) from that point on. So just restrict the warning only to the
case when the PFN in PTE is not zero page.

Link: http://lkml.kernel.org/r/20180824154542.26872-1-jack@suse.cz
Signed-off-by: Jan Kara 
Reviewed-by: Andrew Morton 
Cc: Ross Zwisler 
Cc: Dan Williams 
Cc: Dave Jiang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory.c: recheck page table entry with page table lock held

2018-10-26T23:26:35+00:00

We clear the pte temporarily during read/modify/write update of the pte.
If we take a page fault while the pte is cleared, the application can get
SIGBUS.  One such case is with remap_pfn_range without a backing
vm_ops->fault callback.  do_fault will return SIGBUS in that case.

cpu 0		 				cpu1
mprotect()
ptep_modify_prot_start()/pte cleared.
.
.						page fault.
.
.
prep_modify_prot_commit()

Fix this by taking page table lock and rechecking for pte_none.

[aneesh.kumar@linux.ibm.com: fix crash observed with syzkaller run]
  Link: http://lkml.kernel.org/r/87va6bwlfg.fsf@linux.ibm.com
Link: http://lkml.kernel.org/r/20180926031858.9692-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V 
Acked-by: Kirill A. Shutemov 
Cc: Willem de Bruijn 
Cc: Eric Dumazet 
Cc: Ido Schimmel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: convert insert_pfn() to vm_fault_t

2018-10-26T23:25:20+00:00

All callers convert its errno into a vm_fault_t, so convert it to return a
vm_fault_t directly.

Link: http://lkml.kernel.org/r/20180828145728.11873-11-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Reviewed-by: Andrew Morton 
Cc: Nicolas Pitre 
Cc: Souptick Joarder 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: convert __vm_insert_mixed() to vm_fault_t

2018-10-26T23:25:20+00:00

Both of its callers currently convert its errno return into a vm_fault_t,
so move the conversion into __vm_insert_mixed().

Link: http://lkml.kernel.org/r/20180828145728.11873-10-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Reviewed-by: Andrew Morton 
Cc: Nicolas Pitre 
Cc: Souptick Joarder 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: inline vm_insert_pfn_prot() into caller

2018-10-26T23:25:20+00:00

vm_insert_pfn_prot() is only called from vmf_insert_pfn_prot(), so inline
it and convert some of the errnos into vm_fault codes earlier.

Link: http://lkml.kernel.org/r/20180828145728.11873-9-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Reviewed-by: Andrew Morton 
Cc: Nicolas Pitre 
Cc: Souptick Joarder 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: remove vm_insert_pfn()

2018-10-26T23:25:20+00:00

All callers are now converted to vmf_insert_pfn() so convert
vmf_insert_pfn() from being a compatibility wrapper around vm_insert_pfn()
to being a compatibility wrapper around vmf_insert_pfn_prot().

Link: http://lkml.kernel.org/r/20180828145728.11873-8-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Reviewed-by: Andrew Morton 
Cc: Nicolas Pitre 
Cc: Souptick Joarder 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: make vm_insert_pfn_prot() static

2018-10-26T23:25:19+00:00

Now this is no longer used outside mm/memory.c, make it static.

Link: http://lkml.kernel.org/r/20180828145728.11873-6-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Reviewed-by: Andrew Morton 
Cc: Nicolas Pitre 
Cc: Souptick Joarder 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: introduce vmf_insert_pfn_prot()

2018-10-26T23:25:19+00:00

Like vm_insert_pfn_prot(), but returns a vm_fault_t instead of an errno.
Also unexport vm_insert_pfn_prot as it has no modular users.

Link: http://lkml.kernel.org/r/20180828145728.11873-4-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Reviewed-by: Andrew Morton 
Cc: Nicolas Pitre 
Cc: Souptick Joarder 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: remove vm_insert_mixed()

2018-10-26T23:25:19+00:00

All callers are now converted to vmf_insert_mixed() so convert
vmf_insert_mixed() from being a compatibility wrapper into the real
function.

Link: http://lkml.kernel.org/r/20180828145728.11873-3-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Reviewed-by: Andrew Morton 
Cc: Nicolas Pitre 
Cc: Souptick Joarder 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory: Move mmu_gather and TLB invalidation code into its own file

2018-09-07T14:19:25+00:00

In preparation for maintaining the mmu_gather code as its own entity,
move the implementation out of memory.c and into its own file.

Cc: "Kirill A. Shutemov" 
Cc: Andrew Morton 
Cc: Michal Hocko 
Signed-off-by: Peter Zijlstra 
Signed-off-by: Will Deacon