Re: [PATCH v8] coredump: Add bit 9 of coredump_filter for pre-exit files before dumping

[Randy Dunlap]

Hi,

On 8/7/26 10:27 PM, Xin Zhao wrote:
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index db6167bef..aee03858b 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -1927,7 +1927,7 @@ will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
>  of memory types. If a bit of the bitmask is set, memory segments of the
>  corresponding memory type are dumped, otherwise they are not dumped.
>  
> -The following 9 memory types are supported:
> +The following 10 memory types are supported:
>  
>    - (bit 0) anonymous private memory
>    - (bit 1) anonymous shared memory
> @@ -1939,6 +1939,7 @@ The following 9 memory types are supported:
>    - (bit 6) hugetlb shared memory
>    - (bit 7) DAX private memory
>    - (bit 8) DAX shared memory
> +  - (bit 9) fd list
>  
>    Note that MMIO pages such as frame buffer are never dumped and vDSO pages
>    are always dumped regardless of the bitmask status.
> @@ -1946,13 +1947,19 @@ The following 9 memory types are supported:
>    Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
>    only affected by bit 5-6, and DAX is only affected by bits 7-8.
>  
> -The default value of coredump_filter is 0x33; this means all anonymous memory
> -segments, ELF header pages and hugetlb private memory are dumped.
> +  Note that bit 9 is set by default because tools like systemd-coredump go
> +  through the fds. If you do not set bit 9, files that are not referenced by
> +  any VMA are released before dumping core. Some file release logic, such as
> +  exiting flock or releasing references to shared buffers is executed much
> +  earlier.
> +
> +The default value of coredump_filter is 0x233; this means all anonymous memory
> +segments, ELF header pages, hugetlb private memory and fd list are dumped.
>  
>  If you don't want to dump all shared memory segments attached to pid 1234,
> -write 0x31 to the process's proc file::
> +write 0x231 to the process's proc file::
>  
> -  $ echo 0x31 > /proc/1234/coredump_filter
> +  $ echo 0x231 > /proc/1234/coredump_filter
>  
>  When a new process is created, the process inherits the bitmask status from its
>  parent. It is useful to set up coredump_filter before the program runs.

The proc.rst update LGTM. Thanks.

Acked-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> # for proc.rst

-- 
~Randy