Re: [PATCH v2 1/3] fat: remove cluster allocation size limit

[OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>]

Matheus Alves de Almeida <matheus.aalmeida@inf.ufrgs.br> writes:

> fat_alloc_clusters() currently BUG()s when asked to allocate more than
> MAX_BUF_PER_PAGE / 2 clusters. This limit comes from the buffer_head
> array used to defer syncing and mirroring.
>
> Remove the allocation size limit by doing buffer_head batching like
> fat_free_clusters() does.
>
> Signed-off-by: Matheus Alves de Almeida <matheus.aalmeida@inf.ufrgs.br>

Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Looks good. Thanks.

> ---
>  fs/fat/fatent.c | 44 +++++++++++++++++++++++++++++++-------------
>  1 file changed, 31 insertions(+), 13 deletions(-)
>
> diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
> index f0801d99d..bfab8eab5 100644
> --- a/fs/fat/fatent.c
> +++ b/fs/fat/fatent.c
> @@ -468,6 +468,26 @@ static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
>  	}
>  }
>  
> +static int fat_flush_bhs(struct super_block *sb, struct buffer_head **bhs,
> +			 int *nr_bhs, bool sync)
> +{
> +	int err, i;
> +
> +	if (sync) {
> +		err = fat_sync_bhs(bhs, *nr_bhs);
> +		if (err)
> +			return err;
> +	}
> +	err = fat_mirror_bhs(sb, bhs, *nr_bhs);
> +	if (err)
> +		return err;
> +	for (i = 0; i < *nr_bhs; i++)
> +		brelse(bhs[i]);
> +	*nr_bhs = 0;
> +
> +	return 0;
> +}
> +
>  int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
>  {
>  	struct super_block *sb = inode->i_sb;
> @@ -477,8 +497,6 @@ int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
>  	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
>  	int i, count, err, nr_bhs, idx_clus;
>  
> -	BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));	/* fixed limit */
> -
>  	lock_fat(sbi);
>  	if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
>  	    sbi->free_clusters < nr_cluster) {
> @@ -509,14 +527,21 @@ int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
>  				if (prev_ent.nr_bhs)
>  					ops->ent_put(&prev_ent, entry);
>  
> -				fat_collect_bhs(bhs, &nr_bhs, &fatent);
> -
>  				sbi->prev_free = entry;
>  				if (sbi->free_clusters != -1)
>  					sbi->free_clusters--;
>  
>  				cluster[idx_clus] = entry;
>  				idx_clus++;
> +
> +				if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
> +					err = fat_flush_bhs(sb, bhs, &nr_bhs,
> +							    inode_needs_sync(inode));
> +					if (err)
> +						goto out;
> +				}
> +				fat_collect_bhs(bhs, &nr_bhs, &fatent);
> +
>  				if (idx_clus == nr_cluster)
>  					goto out;
>  
> @@ -606,17 +631,10 @@ int fat_free_clusters(struct inode *inode, int cluster)
>  		}
>  
>  		if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
> -			if (sb->s_flags & SB_SYNCHRONOUS) {
> -				err = fat_sync_bhs(bhs, nr_bhs);
> -				if (err)
> -					goto error;
> -			}
> -			err = fat_mirror_bhs(sb, bhs, nr_bhs);
> +			err = fat_flush_bhs(sb, bhs, &nr_bhs,
> +					    sb->s_flags & SB_SYNCHRONOUS);
>  			if (err)
>  				goto error;
> -			for (i = 0; i < nr_bhs; i++)
> -				brelse(bhs[i]);
> -			nr_bhs = 0;
>  		}
>  		fat_collect_bhs(bhs, &nr_bhs, &fatent);
>  	} while (cluster != FAT_ENT_EOF);

-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>