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mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()
Avoid allocating a new VMA when it a vma modification can occur. When a brk() can expand or contract a VMA, then the single store operation will only modify one index of the maple tree instead of causing a node to split or coalesce. This avoids unnecessary allocations/frees of maple tree nodes and VMAs. Move some limit & flag verifications out of the do_brk_flags() function to use only relevant checks in the code path of bkr() and vm_brk_flags(). Set the vma to check if it can expand in vm_brk_flags() if extra criteria are met. Drop userfaultfd from do_brk_flags() path and only use it in vm_brk_flags() path since that is the only place a munmap will happen. Add a wraper for munmap for the brk case called do_brk_munmap(). Link: https://lkml.kernel.org/r/20220906194824.2110408-23-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> Tested-by: Yu Zhao <yuzhao@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett
Andrew Morton
parent
94d815b279
commit
2e7ce7d354
237
mm/mmap.c
237
mm/mmap.c
@ -147,17 +147,40 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
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return next;
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}
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static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
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struct list_head *uf);
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/*
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* check_brk_limits() - Use platform specific check of range & verify mlock
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* limits.
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* @addr: The address to check
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* @len: The size of increase.
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*
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* Return: 0 on success.
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*/
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static int check_brk_limits(unsigned long addr, unsigned long len)
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{
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unsigned long mapped_addr;
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mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
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if (IS_ERR_VALUE(mapped_addr))
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return mapped_addr;
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return mlock_future_check(current->mm, current->mm->def_flags, len);
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}
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static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
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unsigned long newbrk, unsigned long oldbrk,
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struct list_head *uf);
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static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *brkvma,
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unsigned long addr, unsigned long request,
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unsigned long flags);
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SYSCALL_DEFINE1(brk, unsigned long, brk)
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{
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unsigned long newbrk, oldbrk, origbrk;
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *next;
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struct vm_area_struct *brkvma, *next = NULL;
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unsigned long min_brk;
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bool populate;
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bool downgraded = false;
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LIST_HEAD(uf);
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MA_STATE(mas, &mm->mm_mt, 0, 0);
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if (mmap_write_lock_killable(mm))
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return -EINTR;
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@ -199,35 +222,52 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
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/*
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* Always allow shrinking brk.
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* __do_munmap() may downgrade mmap_lock to read.
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* do_brk_munmap() may downgrade mmap_lock to read.
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*/
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if (brk <= mm->brk) {
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int ret;
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/* Search one past newbrk */
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mas_set(&mas, newbrk);
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brkvma = mas_find(&mas, oldbrk);
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BUG_ON(brkvma == NULL);
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if (brkvma->vm_start >= oldbrk)
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goto out; /* mapping intersects with an existing non-brk vma. */
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/*
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* mm->brk must to be protected by write mmap_lock so update it
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* before downgrading mmap_lock. When __do_munmap() fails,
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* mm->brk will be restored from origbrk.
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* mm->brk must be protected by write mmap_lock.
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* do_brk_munmap() may downgrade the lock, so update it
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* before calling do_brk_munmap().
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*/
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mm->brk = brk;
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ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
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if (ret < 0) {
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mm->brk = origbrk;
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goto out;
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} else if (ret == 1) {
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mas.last = oldbrk - 1;
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ret = do_brk_munmap(&mas, brkvma, newbrk, oldbrk, &uf);
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if (ret == 1) {
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downgraded = true;
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}
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goto success;
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goto success;
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} else if (!ret)
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goto success;
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mm->brk = origbrk;
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goto out;
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}
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/* Check against existing mmap mappings. */
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next = find_vma(mm, oldbrk);
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if (check_brk_limits(oldbrk, newbrk - oldbrk))
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goto out;
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/*
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* Only check if the next VMA is within the stack_guard_gap of the
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* expansion area
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*/
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mas_set(&mas, oldbrk);
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next = mas_find(&mas, newbrk - 1 + PAGE_SIZE + stack_guard_gap);
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if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
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goto out;
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brkvma = mas_prev(&mas, mm->start_brk);
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/* Ok, looks good - let it rip. */
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if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
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if (do_brk_flags(&mas, brkvma, oldbrk, newbrk - oldbrk, 0) < 0)
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goto out;
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mm->brk = brk;
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success:
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@ -2762,38 +2802,55 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
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}
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/*
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* this is really a simplified "do_mmap". it only handles
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* anonymous maps. eventually we may be able to do some
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* brk-specific accounting here.
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* brk_munmap() - Unmap a parital vma.
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* @mas: The maple tree state.
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* @vma: The vma to be modified
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* @newbrk: the start of the address to unmap
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* @oldbrk: The end of the address to unmap
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* @uf: The userfaultfd list_head
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*
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* Returns: 1 on success.
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* unmaps a partial VMA mapping. Does not handle alignment, downgrades lock if
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* possible.
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*/
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static int do_brk_flags(unsigned long addr, unsigned long len,
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unsigned long flags, struct list_head *uf)
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static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
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unsigned long newbrk, unsigned long oldbrk,
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struct list_head *uf)
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{
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struct mm_struct *mm = vma->vm_mm;
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int ret;
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arch_unmap(mm, newbrk, oldbrk);
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ret = __do_munmap(mm, newbrk, oldbrk - newbrk, uf, true);
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validate_mm_mt(mm);
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return ret;
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}
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/*
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* do_brk_flags() - Increase the brk vma if the flags match.
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* @mas: The maple tree state.
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* @addr: The start address
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* @len: The length of the increase
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* @vma: The vma,
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* @flags: The VMA Flags
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*
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* Extend the brk VMA from addr to addr + len. If the VMA is NULL or the flags
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* do not match then create a new anonymous VMA. Eventually we may be able to
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* do some brk-specific accounting here.
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*/
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static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
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unsigned long addr, unsigned long len,
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unsigned long flags)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma, *prev;
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pgoff_t pgoff = addr >> PAGE_SHIFT;
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int error;
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unsigned long mapped_addr;
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struct vm_area_struct *prev = NULL;
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validate_mm_mt(mm);
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/* Until we need other flags, refuse anything except VM_EXEC. */
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if ((flags & (~VM_EXEC)) != 0)
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return -EINVAL;
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/*
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* Check against address space limits by the changed size
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* Note: This happens *after* clearing old mappings in some code paths.
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*/
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flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
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mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
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if (IS_ERR_VALUE(mapped_addr))
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return mapped_addr;
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error = mlock_future_check(mm, mm->def_flags, len);
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if (error)
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return error;
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/* Clear old maps, set up prev and uf */
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if (munmap_vma_range(mm, addr, len, &prev, uf))
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return -ENOMEM;
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/* Check against address space limits *after* clearing old maps... */
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if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
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return -ENOMEM;
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@ -2803,30 +2860,54 @@ static int do_brk_flags(unsigned long addr, unsigned long len,
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if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
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return -ENOMEM;
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/* Can we just expand an old private anonymous mapping? */
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vma = vma_merge(mm, prev, addr, addr + len, flags,
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NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX, NULL);
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if (vma)
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goto out;
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/*
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* create a vma struct for an anonymous mapping
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* Expand the existing vma if possible; Note that singular lists do not
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* occur after forking, so the expand will only happen on new VMAs.
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*/
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vma = vm_area_alloc(mm);
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if (!vma) {
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vm_unacct_memory(len >> PAGE_SHIFT);
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return -ENOMEM;
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if (vma &&
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(!vma->anon_vma || list_is_singular(&vma->anon_vma_chain)) &&
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((vma->vm_flags & ~VM_SOFTDIRTY) == flags)) {
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mas->index = vma->vm_start;
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mas->last = addr + len - 1;
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vma_adjust_trans_huge(vma, addr, addr + len, 0);
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if (vma->anon_vma) {
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anon_vma_lock_write(vma->anon_vma);
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anon_vma_interval_tree_pre_update_vma(vma);
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}
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vma->vm_end = addr + len;
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vma->vm_flags |= VM_SOFTDIRTY;
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if (mas_store_gfp(mas, vma, GFP_KERNEL))
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goto mas_expand_failed;
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if (vma->anon_vma) {
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anon_vma_interval_tree_post_update_vma(vma);
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anon_vma_unlock_write(vma->anon_vma);
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}
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khugepaged_enter_vma(vma, flags);
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goto out;
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}
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prev = vma;
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/* create a vma struct for an anonymous mapping */
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vma = vm_area_alloc(mm);
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if (!vma)
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goto vma_alloc_fail;
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vma_set_anonymous(vma);
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vma->vm_start = addr;
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vma->vm_end = addr + len;
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vma->vm_pgoff = pgoff;
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vma->vm_pgoff = addr >> PAGE_SHIFT;
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vma->vm_flags = flags;
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vma->vm_page_prot = vm_get_page_prot(flags);
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if (vma_link(mm, vma, prev))
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goto no_vma_link;
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mas_set_range(mas, vma->vm_start, addr + len - 1);
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if (mas_store_gfp(mas, vma, GFP_KERNEL))
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goto mas_store_fail;
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if (!prev)
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prev = mas_prev(mas, 0);
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__vma_link_list(mm, vma, prev);
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mm->map_count++;
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out:
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perf_event_mmap(vma);
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mm->total_vm += len >> PAGE_SHIFT;
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@ -2837,18 +2918,29 @@ static int do_brk_flags(unsigned long addr, unsigned long len,
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validate_mm_mt(mm);
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return 0;
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no_vma_link:
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mas_store_fail:
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vm_area_free(vma);
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vma_alloc_fail:
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vm_unacct_memory(len >> PAGE_SHIFT);
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return -ENOMEM;
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mas_expand_failed:
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if (vma->anon_vma) {
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anon_vma_interval_tree_post_update_vma(vma);
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anon_vma_unlock_write(vma->anon_vma);
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}
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return -ENOMEM;
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}
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int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma = NULL;
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unsigned long len;
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int ret;
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bool populate;
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LIST_HEAD(uf);
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MA_STATE(mas, &mm->mm_mt, addr, addr);
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len = PAGE_ALIGN(request);
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if (len < request)
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@ -2859,13 +2951,38 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
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if (mmap_write_lock_killable(mm))
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return -EINTR;
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ret = do_brk_flags(addr, len, flags, &uf);
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/* Until we need other flags, refuse anything except VM_EXEC. */
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if ((flags & (~VM_EXEC)) != 0)
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return -EINVAL;
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ret = check_brk_limits(addr, len);
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if (ret)
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goto limits_failed;
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if (find_vma_intersection(mm, addr, addr + len))
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ret = do_munmap(mm, addr, len, &uf);
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if (ret)
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goto munmap_failed;
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vma = mas_prev(&mas, 0);
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if (!vma || vma->vm_end != addr || vma_policy(vma) ||
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!can_vma_merge_after(vma, flags, NULL, NULL,
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addr >> PAGE_SHIFT, NULL_VM_UFFD_CTX, NULL))
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vma = NULL;
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ret = do_brk_flags(&mas, vma, addr, len, flags);
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populate = ((mm->def_flags & VM_LOCKED) != 0);
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mmap_write_unlock(mm);
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userfaultfd_unmap_complete(mm, &uf);
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if (populate && !ret)
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mm_populate(addr, len);
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return ret;
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munmap_failed:
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limits_failed:
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mmap_write_unlock(mm);
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return ret;
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}
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EXPORT_SYMBOL(vm_brk_flags);
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