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author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-02-01 02:08:56 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-02-01 02:08:56 +0300 |
commit | fc8744adc870a8d4366908221508bb113d8b72ee (patch) | |
tree | 755f4c4a1cc30567fde4e60c9cc5e6a889c360b0 /mm/mmap.c | |
parent | 33bfad54b58cf05cfe6678c3ec9235d4bc8db4c2 (diff) | |
download | linux-fc8744adc870a8d4366908221508bb113d8b72ee.tar.xz |
Stop playing silly games with the VM_ACCOUNT flag
The mmap_region() code would temporarily set the VM_ACCOUNT flag for
anonymous shared mappings just to inform shmem_zero_setup() that it
should enable accounting for the resulting shm object. It would then
clear the flag after calling ->mmap (for the /dev/zero case) or doing
shmem_zero_setup() (for the MAP_ANON case).
This just resulted in vma merge issues, but also made for just
unnecessary confusion. Use the already-existing VM_NORESERVE flag for
this instead, and let shmem_{zero|file}_setup() just figure it out from
that.
This also happens to make it obvious that the new DRI2 GEM layer uses a
non-reserving backing store for its object allocation - which is quite
possibly not intentional. But since I didn't want to change semantics
in this patch, I left it alone, and just updated the caller to use the
new flag semantics.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r-- | mm/mmap.c | 48 |
1 files changed, 25 insertions, 23 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index c581df14d0de..214b6a258eeb 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1090,6 +1090,15 @@ int vma_wants_writenotify(struct vm_area_struct *vma) mapping_cap_account_dirty(vma->vm_file->f_mapping); } +/* + * We account for memory if it's a private writeable mapping, + * and VM_NORESERVE wasn't set. + */ +static inline int accountable_mapping(unsigned int vm_flags) +{ + return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE; +} + unsigned long mmap_region(struct file *file, unsigned long addr, unsigned long len, unsigned long flags, unsigned int vm_flags, unsigned long pgoff, @@ -1117,23 +1126,24 @@ munmap_back: if (!may_expand_vm(mm, len >> PAGE_SHIFT)) return -ENOMEM; - if (flags & MAP_NORESERVE) + /* + * Set 'VM_NORESERVE' if we should not account for the + * memory use of this mapping. We only honor MAP_NORESERVE + * if we're allowed to overcommit memory. + */ + if ((flags & MAP_NORESERVE) && sysctl_overcommit_memory != OVERCOMMIT_NEVER) + vm_flags |= VM_NORESERVE; + if (!accountable) vm_flags |= VM_NORESERVE; - if (accountable && (!(flags & MAP_NORESERVE) || - sysctl_overcommit_memory == OVERCOMMIT_NEVER)) { - if (vm_flags & VM_SHARED) { - /* Check memory availability in shmem_file_setup? */ - vm_flags |= VM_ACCOUNT; - } else if (vm_flags & VM_WRITE) { - /* - * Private writable mapping: check memory availability - */ - charged = len >> PAGE_SHIFT; - if (security_vm_enough_memory(charged)) - return -ENOMEM; - vm_flags |= VM_ACCOUNT; - } + /* + * Private writable mapping: check memory availability + */ + if (accountable_mapping(vm_flags)) { + charged = len >> PAGE_SHIFT; + if (security_vm_enough_memory(charged)) + return -ENOMEM; + vm_flags |= VM_ACCOUNT; } /* @@ -1184,14 +1194,6 @@ munmap_back: goto free_vma; } - /* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform - * shmem_zero_setup (perhaps called through /dev/zero's ->mmap) - * that memory reservation must be checked; but that reservation - * belongs to shared memory object, not to vma: so now clear it. - */ - if ((vm_flags & (VM_SHARED|VM_ACCOUNT)) == (VM_SHARED|VM_ACCOUNT)) - vma->vm_flags &= ~VM_ACCOUNT; - /* Can addr have changed?? * * Answer: Yes, several device drivers can do it in their |