On 08/30/2013 10:42 PM, Al Viro wrote:
On Sat, Aug 31, 2013 at 03:35:16AM +0100, Al Viro wrote:
Aha... OK, I see what's going on. We end up with shm_mnt *not* marked
as long-living vfsmount, even though it lives forever. See if the
following helps; if it does (and I very much expect it to), we want to
put it in -stable. As it is, you get slow path in mntput() each time
a file created by shmem_file_setup() gets closed. For no reason whatsoever...
We still want MS_NOUSER on shm_mnt, so we'd better make sure that
shmem_fill_super() sets it on the internal instance... Fixed variant
follows:
Signed-off-by: Al Viro<viro@xxxxxxxxxxxxxxxxxx>
diff --git a/mm/shmem.c b/mm/shmem.c
index e43dc55..5261498 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2615,13 +2615,15 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
* tmpfs instance, limiting inodes to one per page of lowmem;
* but the internal instance is left unlimited.
*/
- if (!(sb->s_flags& MS_NOUSER)) {
+ if (!(sb->s_flags& MS_KERNMOUNT)) {
sbinfo->max_blocks = shmem_default_max_blocks();
sbinfo->max_inodes = shmem_default_max_inodes();
if (shmem_parse_options(data, sbinfo, false)) {
err = -EINVAL;
goto failed;
}
+ } else {
+ sb->s_flags |= MS_NOUSER;
}
sb->s_export_op =&shmem_export_ops;
sb->s_flags |= MS_NOSEC;
@@ -2831,8 +2833,7 @@ int __init shmem_init(void)
goto out2;
}
- shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
- shmem_fs_type.name, NULL);
+ shm_mnt = kern_mount(&shmem_fs_type);
if (IS_ERR(shm_mnt)) {
error = PTR_ERR(shm_mnt);
printk(KERN_ERR "Could not kern_mount tmpfs\n");
Yes, that patch worked. It eliminated the lglock as a bottleneck in the
AIM7 workload. The lg_global_lock did not show up in the perf profile,
whereas the lg_local_lock was only 0.07%.
Regards,
Longman
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