Messages in this thread | | | Subject | Re: [PATCH v2] mm/mremap: Don't account pages in vma_to_resize() | From | Dmitry Safonov <> | Date | Wed, 21 Jul 2021 14:21:54 +0100 |
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On 7/21/21 2:13 PM, Dmitry Safonov wrote: > All this vm_unacct_memory(charged) dance seems to complicate the life > without a good reason. Furthermore, it seems not always done right on > error-pathes in mremap_to(). > And worse than that: this `charged' difference is sometimes > double-accounted for growing MREMAP_DONTUNMAP mremap()s in move_vma(): > : if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) > > Let's not do this. > Account memory in mremap() fast-path for growing VMAs or in move_vma() > for actually moving things. The same simpler way as it's done by > vm_stat_account(), but with a difference to call > security_vm_enough_memory_mm() before copying/adjusting VMA. > > Originally noticed by Chen Wandun: > https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com
The patch by Chen Wandun still makes sense with this v2. Heh :-)
> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Brian Geffon <bgeffon@google.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Chen Wandun <chenwandun@huawei.com> > Cc: Dan Carpenter <dan.carpenter@oracle.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Dave Jiang <dave.jiang@intel.com> > Cc: Hugh Dickins <hughd@google.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Jason Gunthorpe <jgg@ziepe.ca> > Cc: John Hubbard <jhubbard@nvidia.com> > Cc: Kefeng Wang <wangkefeng.wang@huawei.com> > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Minchan Kim <minchan@kernel.org> > Cc: Ralph Campbell <rcampbell@nvidia.com> > Cc: Russell King <linux@armlinux.org.uk> > Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Vishal Verma <vishal.l.verma@intel.com> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Wei Yongjun <weiyongjun1@huawei.com> > Cc: Will Deacon <will@kernel.org> > Fixes: e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()") > Signed-off-by: Dmitry Safonov <dima@arista.com> > --- > mm/mremap.c | 50 ++++++++++++++++++++++---------------------------- > 1 file changed, 22 insertions(+), 28 deletions(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index 5989d3990020..b90c8e732e29 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -565,6 +565,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, > bool *locked, unsigned long flags, > struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap) > { > + long to_account = new_len - old_len; > struct mm_struct *mm = vma->vm_mm; > struct vm_area_struct *new_vma; > unsigned long vm_flags = vma->vm_flags; > @@ -583,6 +584,9 @@ static unsigned long move_vma(struct vm_area_struct *vma, > if (mm->map_count >= sysctl_max_map_count - 3) > return -ENOMEM; > > + if (unlikely(flags & MREMAP_DONTUNMAP)) > + to_account = new_len; > + > if (vma->vm_ops && vma->vm_ops->may_split) { > if (vma->vm_start != old_addr) > err = vma->vm_ops->may_split(vma, old_addr); > @@ -604,8 +608,8 @@ static unsigned long move_vma(struct vm_area_struct *vma, > if (err) > return err; > > - if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) { > - if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) > + if (vm_flags & VM_ACCOUNT) { > + if (security_vm_enough_memory_mm(mm, to_account >> PAGE_SHIFT)) > return -ENOMEM; > } > > @@ -613,8 +617,8 @@ static unsigned long move_vma(struct vm_area_struct *vma, > new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, > &need_rmap_locks); > if (!new_vma) { > - if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) > - vm_unacct_memory(new_len >> PAGE_SHIFT); > + if (vm_flags & VM_ACCOUNT) > + vm_unacct_memory(to_account >> PAGE_SHIFT); > return -ENOMEM; > } > > @@ -708,8 +712,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, > } > > static struct vm_area_struct *vma_to_resize(unsigned long addr, > - unsigned long old_len, unsigned long new_len, unsigned long flags, > - unsigned long *p) > + unsigned long old_len, unsigned long new_len, unsigned long flags) > { > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > @@ -768,13 +771,6 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, > (new_len - old_len) >> PAGE_SHIFT)) > return ERR_PTR(-ENOMEM); > > - if (vma->vm_flags & VM_ACCOUNT) { > - unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; > - if (security_vm_enough_memory_mm(mm, charged)) > - return ERR_PTR(-ENOMEM); > - *p = charged; > - } > - > return vma; > } > > @@ -787,7 +783,6 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > unsigned long ret = -EINVAL; > - unsigned long charged = 0; > unsigned long map_flags = 0; > > if (offset_in_page(new_addr)) > @@ -830,7 +825,7 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, > old_len = new_len; > } > > - vma = vma_to_resize(addr, old_len, new_len, flags, &charged); > + vma = vma_to_resize(addr, old_len, new_len, flags); > if (IS_ERR(vma)) { > ret = PTR_ERR(vma); > goto out; > @@ -853,7 +848,7 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, > ((addr - vma->vm_start) >> PAGE_SHIFT), > map_flags); > if (IS_ERR_VALUE(ret)) > - goto out1; > + goto out; > > /* We got a new mapping */ > if (!(flags & MREMAP_FIXED)) > @@ -862,12 +857,6 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, > ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf, > uf_unmap); > > - if (!(offset_in_page(ret))) > - goto out; > - > -out1: > - vm_unacct_memory(charged); > - > out: > return ret; > } > @@ -899,7 +888,6 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > unsigned long ret = -EINVAL; > - unsigned long charged = 0; > bool locked = false; > bool downgraded = false; > struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX; > @@ -981,7 +969,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, > /* > * Ok, we need to grow.. > */ > - vma = vma_to_resize(addr, old_len, new_len, flags, &charged); > + vma = vma_to_resize(addr, old_len, new_len, flags); > if (IS_ERR(vma)) { > ret = PTR_ERR(vma); > goto out; > @@ -992,10 +980,18 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, > if (old_len == vma->vm_end - addr) { > /* can we just expand the current mapping? */ > if (vma_expandable(vma, new_len - old_len)) { > - int pages = (new_len - old_len) >> PAGE_SHIFT; > + long pages = (new_len - old_len) >> PAGE_SHIFT; > + > + if (vma->vm_flags & VM_ACCOUNT) { > + if (security_vm_enough_memory_mm(mm, pages)) { > + ret = -ENOMEM; > + goto out; > + } > + } > > if (vma_adjust(vma, vma->vm_start, addr + new_len, > vma->vm_pgoff, NULL)) { > + vm_unacct_memory(pages); > ret = -ENOMEM; > goto out; > } > @@ -1034,10 +1030,8 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, > &locked, flags, &uf, &uf_unmap); > } > out: > - if (offset_in_page(ret)) { > - vm_unacct_memory(charged); > + if (offset_in_page(ret)) > locked = false; > - } > if (downgraded) > mmap_read_unlock(current->mm); > else >
-- Dima
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