lkml.org 
[lkml]   [2022]   [Jun]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v10 13/69] mm/mmap: use maple tree for unmapped_area{_topdown}
    On 21.06.22 22:46, Liam Howlett wrote:
    > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
    >
    > The maple tree code was added to find the unmapped area in a previous
    > commit and was checked against what the rbtree returned, but the actual
    > result was never used. Start using the maple tree implementation and
    > remove the rbtree code.
    >
    > Add kernel documentation comment for these functions.
    >
    > Link: https://lkml.kernel.org/r/20220504010716.661115-15-Liam.Howlett@oracle.com
    > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
    > Cc: Catalin Marinas <catalin.marinas@arm.com>
    > Cc: David Howells <dhowells@redhat.com>
    > Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
    > Cc: SeongJae Park <sj@kernel.org>
    > Cc: Vlastimil Babka <vbabka@suse.cz>
    > Cc: Will Deacon <will@kernel.org>
    > Cc: Davidlohr Bueso <dave@stgolabs.net>
    > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    > ---
    > mm/mmap.c | 253 +++++++-----------------------------------------------
    > 1 file changed, 32 insertions(+), 221 deletions(-)
    >
    > diff --git a/mm/mmap.c b/mm/mmap.c
    > index 08845a0317bf..b91d22329418 100644
    > --- a/mm/mmap.c
    > +++ b/mm/mmap.c
    > @@ -2053,250 +2053,61 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
    > return error;
    > }
    >
    > +/* unmapped_area() Find an area between the low_limit and the high_limit with

    /**
    * unmapped_area() - ...

    > + * the correct alignment and offset, all from @info. Note: current->mm is used
    > + * for the search.
    > + *
    > + * @info: The unmapped area information including the range (low_limit -
    > + * hight_limit), the alignment offset and mask.
    > + *
    > + * Return: A memory address or -ENOMEM.
    > + */
    > static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
    > {

    ...

    >
    > +/* unmapped_area_topdown() Find an area between the low_limit and the

    \Dito

    > + * high_limit with * the correct alignment and offset at the highest available
    > + * address, all from * @info. Note: current->mm is used for the search.

    I'm confused about the "*" in the text, but maybe I'm just tired :)

    > + *
    > + * @info: The unmapped area information including the range (low_limit -
    > + * hight_limit), the alignment offset and mask.
    > + *
    > + * Return: A memory address or -ENOMEM.
    > + */
    > static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
    > {

    [...]

    > -found:
    > - /* We found a suitable gap. Clip it with the original high_limit. */
    > - if (gap_end > info->high_limit)
    > - gap_end = info->high_limit;
    > -
    > -found_highest:
    > - /* Compute highest gap address at the desired alignment */
    > - gap_end -= info->length;
    > - gap_end -= (gap_end - info->align_offset) & info->align_mask;
    > -
    > - VM_BUG_ON(gap_end < info->low_limit);
    > - VM_BUG_ON(gap_end < gap_start);

    Can we leave some of these in, please? (same applies to other function)

    I keep getting confused by align_offset. vs align_mask. I *think* this
    is correct, but some checks that we stay in limits and actually have
    proper alignment would be reasonable.


    --
    Thanks,

    David / dhildenb

    \
     
     \ /
      Last update: 2022-06-23 20:26    [W:3.742 / U:0.444 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site