| Message ID | 07433b0f16a152bffb8cee34934a5c040e8e2ad6.1722404078.git.baolin.wang@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] mm: shmem: avoid allocating huge pages larger than MAX_PAGECACHE_ORDER for shmem | expand |
On 31.07.24 07:46, Baolin Wang wrote: > In the shmem_suitable_orders() function, xa_find() is used to check for > conflicts in the pagecache to select suitable huge orders. However, when > checking each huge order in every loop, the aligned index is calculated > from the previous iteration, which may cause suitable huge orders to be > missed. > > We should use the original index each time in the loop to calculate a > new aligned index for checking conflicts to avoid this issue. > > Fixes: e7a2ab7b3bb5 ("mm: shmem: add mTHP support for anonymous shmem") > Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> > --- > mm/shmem.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index a4332a97558c..6e9836b1bd1d 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1686,6 +1686,7 @@ static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault > unsigned long orders) > { > struct vm_area_struct *vma = vmf->vma; > + pgoff_t aligned_index; > unsigned long pages; > int order; > > @@ -1697,9 +1698,9 @@ static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault > order = highest_order(orders); > while (orders) { > pages = 1UL << order; > - index = round_down(index, pages); > - if (!xa_find(&mapping->i_pages, &index, > - index + pages - 1, XA_PRESENT)) > + aligned_index = round_down(index, pages); > + if (!xa_find(&mapping->i_pages, &aligned_index, > + aligned_index + pages - 1, XA_PRESENT)) > break; > order = next_order(&orders, order); > } Acked-by: David Hildenbrand <david@redhat.com>
diff --git a/mm/shmem.c b/mm/shmem.c index a4332a97558c..6e9836b1bd1d 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1686,6 +1686,7 @@ static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault unsigned long orders) { struct vm_area_struct *vma = vmf->vma; + pgoff_t aligned_index; unsigned long pages; int order; @@ -1697,9 +1698,9 @@ static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault order = highest_order(orders); while (orders) { pages = 1UL << order; - index = round_down(index, pages); - if (!xa_find(&mapping->i_pages, &index, - index + pages - 1, XA_PRESENT)) + aligned_index = round_down(index, pages); + if (!xa_find(&mapping->i_pages, &aligned_index, + aligned_index + pages - 1, XA_PRESENT)) break; order = next_order(&orders, order); }
In the shmem_suitable_orders() function, xa_find() is used to check for conflicts in the pagecache to select suitable huge orders. However, when checking each huge order in every loop, the aligned index is calculated from the previous iteration, which may cause suitable huge orders to be missed. We should use the original index each time in the loop to calculate a new aligned index for checking conflicts to avoid this issue. Fixes: e7a2ab7b3bb5 ("mm: shmem: add mTHP support for anonymous shmem") Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> --- mm/shmem.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)