linux-kernel - Re: [PATCH v2] ocfs2: fixing global bitmap allocating failure for discontig type

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Message-ID: <1f3049dc-5536-4a27-8768-b264be062f7c@linux.alibaba.com>
Date: Wed, 2 Apr 2025 19:08:17 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Heming Zhao <heming.zhao@...e.com>, akpm <akpm@...ux-foundation.org>
Cc: ocfs2-devel@...ts.linux.dev, linux-kernel@...r.kernel.org,
 gautham.ananthakrishna@...cle.com
Subject: Re: [PATCH v2] ocfs2: fixing global bitmap allocating failure for
 discontig type



On 2025/4/1 22:26, Heming Zhao wrote:
> The commit 4eb7b93e0310 ("ocfs2: improve write IO performance when
> fragmentation is high") introduced a regression. In the discontiguous
> extent allocation case, ocfs2_cluster_group_search() is comparing with
> the wrong target length, which causes allocation failure.
> 
> Call stack:
> ocfs2_mkdir()
>  ocfs2_reserve_new_inode()
>   ocfs2_reserve_suballoc_bits()
>    ocfs2_block_group_alloc()
>     ocfs2_block_group_alloc_discontig()
>      __ocfs2_claim_clusters()
>       ocfs2_claim_suballoc_bits()
>        ocfs2_search_chain()
>         ocfs2_cluster_group_search()
> 
> Reported-by: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>
> Fixes: 4eb7b93e0310 ("ocfs2: improve write IO performance when fragmentation is high")
> Signed-off-by: Heming Zhao <heming.zhao@...e.com>

Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
Tested-by: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>

> ---
> v1 -> v2: OCFS2_AC_USE_MAIN_DISCONTIG type requires separate handling,
>           with all other types proceeding as before.
> ---
>  fs/ocfs2/suballoc.c | 10 ++++++++--
>  fs/ocfs2/suballoc.h |  1 +
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
> index f7b483f0de2a..fde75f2af37a 100644
> --- a/fs/ocfs2/suballoc.c
> +++ b/fs/ocfs2/suballoc.c
> @@ -698,10 +698,12 @@ static int ocfs2_block_group_alloc(struct ocfs2_super *osb,
>  
>  	bg_bh = ocfs2_block_group_alloc_contig(osb, handle, alloc_inode,
>  					       ac, cl);
> -	if (PTR_ERR(bg_bh) == -ENOSPC)
> +	if (PTR_ERR(bg_bh) == -ENOSPC) {
> +		ac->ac_which = OCFS2_AC_USE_MAIN_DISCONTIG;
>  		bg_bh = ocfs2_block_group_alloc_discontig(handle,
>  							  alloc_inode,
>  							  ac, cl);
> +	}
>  	if (IS_ERR(bg_bh)) {
>  		status = PTR_ERR(bg_bh);
>  		bg_bh = NULL;
> @@ -2365,7 +2367,8 @@ int __ocfs2_claim_clusters(handle_t *handle,
>  	BUG_ON(ac->ac_bits_given >= ac->ac_bits_wanted);
>  
>  	BUG_ON(ac->ac_which != OCFS2_AC_USE_LOCAL
> -	       && ac->ac_which != OCFS2_AC_USE_MAIN);
> +	       && ac->ac_which != OCFS2_AC_USE_MAIN
> +	       && ac->ac_which != OCFS2_AC_USE_MAIN_DISCONTIG);
>  
>  	if (ac->ac_which == OCFS2_AC_USE_LOCAL) {
>  		WARN_ON(min_clusters > 1);
> @@ -2429,6 +2432,9 @@ int ocfs2_claim_clusters(handle_t *handle,
>  {
>  	unsigned int bits_wanted = ac->ac_bits_wanted - ac->ac_bits_given;
>  
> +	if (ac->ac_which == OCFS2_AC_USE_MAIN_DISCONTIG)
> +		bits_wanted = min_clusters;
> +
>  	return __ocfs2_claim_clusters(handle, ac, min_clusters,
>  				      bits_wanted, cluster_start, num_clusters);
>  }
> diff --git a/fs/ocfs2/suballoc.h b/fs/ocfs2/suballoc.h
> index b481b834857d..bcf2ed4a8631 100644
> --- a/fs/ocfs2/suballoc.h
> +++ b/fs/ocfs2/suballoc.h
> @@ -29,6 +29,7 @@ struct ocfs2_alloc_context {
>  #define OCFS2_AC_USE_MAIN  2
>  #define OCFS2_AC_USE_INODE 3
>  #define OCFS2_AC_USE_META  4
> +#define OCFS2_AC_USE_MAIN_DISCONTIG  5
>  	u32    ac_which;
>  
>  	/* these are used by the chain search */