On 10/25/24 14:26, Lorenzo Stoakes wrote:
> Rather than trying to merge again when ostensibly allocating a new VMA,
> instead defer until the VMA is added and attempt to merge the existing
> range.
>
> This way we have no complicated unwinding logic midway through the process
> of mapping the VMA.
>
> In addition this removes limitations on the VMA not being able to be the
> first in the virtual memory address space which was previously implicitly
> required.
>
> In theory, for this very same reason, we should unconditionally attempt
> merge here, however this is likely to have a performance impact so it is
> better to avoid this given the unlikely outcome of a merge.
>
> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> ---
> mm/vma.c | 55 ++++++++++++++-----------------------------------------
> 1 file changed, 14 insertions(+), 41 deletions(-)
>
> diff --git a/mm/vma.c b/mm/vma.c
> index 7c690be67910..7194f9449c60 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -19,6 +19,7 @@ struct mmap_state {
> struct file *file;
>
> unsigned long charged;
> + bool retry_merge;
>
> struct vm_area_struct *prev;
> struct vm_area_struct *next;
> @@ -2278,8 +2279,9 @@ static int __mmap_prepare(struct mmap_state *map, struct list_head *uf)
> return 0;
> }
>
> +
> static int __mmap_new_file_vma(struct mmap_state *map,
> - struct vm_area_struct **vmap, bool *mergedp)
> + struct vm_area_struct **vmap)
AFAICS **vmap could become *vma now
> {
> struct vma_iterator *vmi = map->vmi;
> struct vm_area_struct *vma = *vmap;
