Re: [PATCH 2/2] Limit the size of vmcore-dmesg.txt to 2G

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On Thu, Aug 15, 2019 at 11:37:56AM +0800, Lianbo Jiang wrote:
> With some corrupted vmcore files, the vmcore-dmesg.txt file may grow
> forever till the kdump disk becomes full, and also probably causes
> the disk error messages as follow:
> ...
> sd 0:0:0:0: [sda] tag#6 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
> sd 0:0:0:0: [sda] tag#6 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
> blk_update_request: I/O error, dev sda, sector 134630552
> sd 0:0:0:0: [sda] tag#7 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
> sd 0:0:0:0: [sda] tag#7 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
> blk_update_request: I/O error, dev sda, sector 134630552
> ...
> 
> If vmcore-dmesg.txt occupies the whole disk, the vmcore can not be
> saved, this is also a problem.
> 
> Lets limit the size of vmcore-dmesg.txt to avoid such problems.
> 
> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>

Thanks, this looks good to me.

Please repost this patch with an updated version of Patch 1/2.

> ---
>  vmcore-dmesg/vmcore-dmesg.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
> index ff0d540c9130..5ada3566972b 100644
> --- a/vmcore-dmesg/vmcore-dmesg.c
> +++ b/vmcore-dmesg/vmcore-dmesg.c
> @@ -1,8 +1,18 @@
>  #include <elf_info.h>
>  
> +/* stole this macro from kernel printk.c */
> +#define LOG_BUF_LEN_MAX (uint32_t)(1 << 31)
> +
>  static void write_to_stdout(char *buf, unsigned int nr)
>  {
>  	ssize_t ret;
> +	static uint32_t n_bytes = 0;
> +
> +	n_bytes += nr;
> +	if (n_bytes > LOG_BUF_LEN_MAX) {
> +		fprintf(stderr, "The vmcore-dmesg.txt over 2G in size is not supported.\n");
> +		exit(55);
> +	}
>  
>  	ret = write(STDOUT_FILENO, buf, nr);
>  	if (ret != nr) {
> -- 
> 2.17.1
> 
> 
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> 

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