[PATCH v2 2/2] ocfs2: add trimfs lock to avoid duplicated trims in cluster

From: Gang He
Date: Thu Dec 14 2017 - 00:15:35 EST


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.

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@xxxxxxxx>
---
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);
--
1.8.5.6