smb3: allow controlling length of time directory entries are cached with dir leases

Currently with directory leases we cache directory contents for a fixed period
of time (default 30 seconds) but for many workloads this is too short.  Allow
configuring the maximum amount of time directory entries are cached when a
directory lease is held on that directory. Add module load parm "max_dir_cache"

For example to set the timeout to 10 minutes you would do:

  echo 600 > /sys/module/cifs/parameters/dir_cache_timeout

or to disable caching directory contents:

  echo 0 > /sys/module/cifs/parameters/dir_cache_timeout

Reviewed-by: Bharath SM <bharathsm@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index 73c44e097a69..52612bb52bd7 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -117,6 +117,10 @@ module_param(cifs_max_pending, uint, 0444);
 MODULE_PARM_DESC(cifs_max_pending, "Simultaneous requests to server for "
 				   "CIFS/SMB1 dialect (N/A for SMB3) "
 				   "Default: 32767 Range: 2 to 32767.");
+unsigned int dir_cache_timeout = 30;
+module_param(dir_cache_timeout, uint, 0644);
+MODULE_PARM_DESC(dir_cache_timeout, "Number of seconds to cache directory contents for which we have a lease. Default: 30 "
+				 "Range: 1 to 65000 seconds, 0 to disable caching dir contents");
 #ifdef CONFIG_CIFS_STATS2
 unsigned int slow_rsp_threshold = 1;
 module_param(slow_rsp_threshold, uint, 0644);
@@ -1679,6 +1683,12 @@ init_cifs(void)
 			 CIFS_MAX_REQ);
 	}
 
+	/* Limit max to about 18 hours, and setting to zero disables directory entry caching */
+	if (dir_cache_timeout > 65000) {
+		dir_cache_timeout = 65000;
+		cifs_dbg(VFS, "dir_cache_timeout set to max of 65000 seconds\n");
+	}
+
 	cifsiod_wq = alloc_workqueue("cifsiod", WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
 	if (!cifsiod_wq) {
 		rc = -ENOMEM;