linux-kernel - Re: [PATCH 02/17] staging: lustre: fix bug in osc_enter_cache

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Date:   Wed, 7 Mar 2018 20:51:39 +0000
From:   "Dilger, Andreas" <andreas.dilger@...el.com>
To:     NeilBrown <neilb@...e.com>
CC:     "Drokin, Oleg" <oleg.drokin@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        James Simmons <jsimmons@...radead.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH 02/17] staging: lustre: fix bug in osc_enter_cache_try

On Mar 1, 2018, at 16:31, NeilBrown <neilb@...e.com> wrote:
> 
> The lustre-release patch commit bdc5bb52c554 ("LU-4933 osc:
> Automatically increase the max_dirty_mb") changed
> 
> -       if (cli->cl_dirty + PAGE_CACHE_SIZE <= cli->cl_dirty_max &&
> +       if (cli->cl_dirty_pages < cli->cl_dirty_max_pages &&
> 
> When this patch landed in Linux a couple of years later, it landed as
> 
> -       if (cli->cl_dirty + PAGE_SIZE <= cli->cl_dirty_max &&
> +       if (cli->cl_dirty_pages <= cli->cl_dirty_max_pages &&
> 
> which is clearly different ('<=' vs '<'), and allows cl_dirty_pages to
> increase beyond cl_dirty_max_pages - which causes a latter assertion
> to fails.
> 
> Fixes: 3147b268400a ("staging: lustre: osc: Automatically increase the max_dirty_mb")
> Signed-off-by: NeilBrown <neilb@...e.com>

Reviewed-by: Andreas Dilger <andreas.dilger@...el.com>

> ---
> drivers/staging/lustre/lustre/include/obd.h   |    2 +-
> drivers/staging/lustre/lustre/osc/osc_cache.c |    2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lustre/include/obd.h b/drivers/staging/lustre/lustre/include/obd.h
> index 4368f4e9f208..f1233ca7d337 100644
> --- a/drivers/staging/lustre/lustre/include/obd.h
> +++ b/drivers/staging/lustre/lustre/include/obd.h
> @@ -191,7 +191,7 @@ struct client_obd {
> 	struct sptlrpc_flavor    cl_flvr_mgc;   /* fixed flavor of mgc->mgs */
> 
> 	/* the grant values are protected by loi_list_lock below */
> -	unsigned long		 cl_dirty_pages;	/* all _dirty_ in pahges */
> +	unsigned long		 cl_dirty_pages;	/* all _dirty_ in pages */
> 	unsigned long		 cl_dirty_max_pages;	/* allowed w/o rpc */
> 	unsigned long		 cl_dirty_transit;	/* dirty synchronous */
> 	unsigned long		 cl_avail_grant;	/* bytes of credit for ost */
> diff --git a/drivers/staging/lustre/lustre/osc/osc_cache.c b/drivers/staging/lustre/lustre/osc/osc_cache.c
> index 1c70a504ee89..459503727ce3 100644
> --- a/drivers/staging/lustre/lustre/osc/osc_cache.c
> +++ b/drivers/staging/lustre/lustre/osc/osc_cache.c
> @@ -1529,7 +1529,7 @@ static int osc_enter_cache_try(struct client_obd *cli,
> 	if (rc < 0)
> 		return 0;
> 
> -	if (cli->cl_dirty_pages <= cli->cl_dirty_max_pages &&
> +	if (cli->cl_dirty_pages < cli->cl_dirty_max_pages &&
> 	    atomic_long_read(&obd_dirty_pages) + 1 <= obd_max_dirty_pages) {
> 		osc_consume_write_grant(cli, &oap->oap_brw_page);
> 		if (transient) {
> 
> 

Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation