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SubjectRe: [Ocfs2-devel] [PATCH v2 2/2] ocfs2: add trimfs lock to avoid duplicated trims in cluster
Hi Gang,

On 2017/12/14 13:14, Gang He wrote:
> As you know, ocfs2 has support trim the underlying disk via
> fstrim command. But there is a problem, ocfs2 is a shared disk
> cluster file system, if the user configures a scheduled fstrim
> job on each file system node, this will trigger multiple nodes
> trim a shared disk simultaneously, it is very wasteful for CPU
> and IO consumption, also might negatively affect the lifetime
> of poor-quality SSD devices.
> Then, we introduce a trimfs dlm lock to communicate with each
> other in this case, which will make only one fstrim command to
> do the trimming on a shared disk among the cluster, the fstrim
> commands from the other nodes should wait for the first fstrim
> to finish and returned success directly, to avoid running a the
> same trim on the shared disk again.
>
For the same purpose, can we take global bitmap meta lock EXMODE instead of
add a new trimfs dlm lock?

Thanks,
Alex

> Compare with first version, I change the fstrim commands' returned
> value and behavior in case which meets a fstrim command is running
> on a shared disk.
>
> Signed-off-by: Gang He <ghe@suse.com>
> ---
> fs/ocfs2/alloc.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
> index ab5105f..5c9c3e2 100644
> --- a/fs/ocfs2/alloc.c
> +++ b/fs/ocfs2/alloc.c
> @@ -7382,6 +7382,7 @@ int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range)
> struct buffer_head *gd_bh = NULL;
> struct ocfs2_dinode *main_bm;
> struct ocfs2_group_desc *gd = NULL;
> + struct ocfs2_trim_fs_info info, *pinfo = NULL;
>
> start = range->start >> osb->s_clustersize_bits;
> len = range->len >> osb->s_clustersize_bits;
> @@ -7419,6 +7420,42 @@ int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range)
>
> trace_ocfs2_trim_fs(start, len, minlen);
>
> + ocfs2_trim_fs_lock_res_init(osb);
> + ret = ocfs2_trim_fs_lock(osb, NULL, 1);
> + if (ret < 0) {
> + if (ret != -EAGAIN) {
> + mlog_errno(ret);
> + ocfs2_trim_fs_lock_res_uninit(osb);
> + goto out_unlock;
> + }
> +
> + mlog(ML_NOTICE, "Wait for trim on device (%s) to "
> + "finish, which is running from another node.\n",
> + osb->dev_str);
> + ret = ocfs2_trim_fs_lock(osb, &info, 0);
> + if (ret < 0) {
> + mlog_errno(ret);
> + ocfs2_trim_fs_lock_res_uninit(osb);
> + goto out_unlock;
> + }
> +
> + if (info.tf_valid && info.tf_success &&
> + info.tf_start == start && info.tf_len == len &&
> + info.tf_minlen == minlen) {
> + /* Avoid sending duplicated trim to a shared device */
> + mlog(ML_NOTICE, "The same trim on device (%s) was "
> + "just done from node (%u), return.\n",
> + osb->dev_str, info.tf_nodenum);
> + range->len = info.tf_trimlen;
> + goto out_trimunlock;
> + }
> + }
> +
> + info.tf_nodenum = osb->node_num;
> + info.tf_start = start;
> + info.tf_len = len;
> + info.tf_minlen = minlen;
> +
> /* Determine first and last group to examine based on start and len */
> first_group = ocfs2_which_cluster_group(main_bm_inode, start);
> if (first_group == osb->first_cluster_group_blkno)
> @@ -7463,6 +7500,13 @@ int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range)
> group += ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg);
> }
> range->len = trimmed * sb->s_blocksize;
> +
> + info.tf_trimlen = range->len;
> + info.tf_success = (ret ? 0 : 1);
> + pinfo = &info;
> +out_trimunlock:
> + ocfs2_trim_fs_unlock(osb, pinfo);
> + ocfs2_trim_fs_lock_res_uninit(osb);
> out_unlock:
> ocfs2_inode_unlock(main_bm_inode, 0);
> brelse(main_bm_bh);
>

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