LinuxLists.cc - [RFC, PATCH, RESEND] fs: push rcu_barrier() from deactivate_locked

2012-06-08 21:40:10

Subject: [RFC, PATCH, RESEND] fs: push rcu_barrier() from deactivate_locked_super() to filesystems

From: "Kirill A. Shutemov" <[email protected]>

Sorry for resend. Original mail had too long cc list.

====
There's no reason to call rcu_barrier() on every deactivate_locked_super().
We only need to make sure that all delayed rcu free inodes are flushed
before we destroy related cache.

Removing rcu_barrier() from deactivate_locked_super() affects some
fas paths. E.g. on my machine exit_group() of a last process in IPC
namespace takes 0.07538s. rcu_barrier() takes 0.05188s of that time.

Signed-off-by: Kirill A. Shutemov <[email protected]>
---
fs/9p/v9fs.c | 5 +++++
fs/adfs/super.c | 5 +++++
fs/affs/super.c | 5 +++++
fs/afs/super.c | 5 +++++
fs/befs/linuxvfs.c | 5 +++++
fs/bfs/inode.c | 5 +++++
fs/btrfs/extent_io.c | 6 ++++++
fs/btrfs/inode.c | 5 +++++
fs/ceph/super.c | 5 +++++
fs/cifs/cifsfs.c | 5 +++++
fs/coda/inode.c | 5 +++++
fs/ecryptfs/main.c | 6 ++++++
fs/efs/super.c | 5 +++++
fs/exofs/super.c | 5 +++++
fs/ext2/super.c | 5 +++++
fs/ext3/super.c | 5 +++++
fs/ext4/super.c | 5 +++++
fs/fat/inode.c | 5 +++++
fs/freevxfs/vxfs_super.c | 5 +++++
fs/fuse/inode.c | 6 ++++++
fs/hfs/super.c | 6 ++++++
fs/hfsplus/super.c | 6 ++++++
fs/hpfs/super.c | 5 +++++
fs/hugetlbfs/inode.c | 5 +++++
fs/isofs/inode.c | 5 +++++
fs/jffs2/super.c | 6 ++++++
fs/jfs/super.c | 6 ++++++
fs/logfs/inode.c | 5 +++++
fs/minix/inode.c | 5 +++++
fs/ncpfs/inode.c | 5 +++++
fs/nfs/inode.c | 5 +++++
fs/nilfs2/super.c | 6 ++++++
fs/ntfs/super.c | 6 ++++++
fs/ocfs2/dlmfs/dlmfs.c | 5 +++++
fs/ocfs2/super.c | 5 +++++
fs/openpromfs/inode.c | 5 +++++
fs/qnx4/inode.c | 5 +++++
fs/qnx6/inode.c | 5 +++++
fs/reiserfs/super.c | 5 +++++
fs/romfs/super.c | 5 +++++
fs/squashfs/super.c | 5 +++++
fs/super.c | 6 ------
fs/sysv/inode.c | 5 +++++
fs/ubifs/super.c | 6 ++++++
fs/udf/super.c | 5 +++++
fs/ufs/super.c | 5 +++++
fs/xfs/xfs_super.c | 5 +++++
47 files changed, 240 insertions(+), 6 deletions(-)

diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index b85efa7..392c5da 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -560,6 +560,11 @@ static int v9fs_init_inode_cache(void)
*/
static void v9fs_destroy_inode_cache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(v9fs_inode_cache);
}

diff --git a/fs/adfs/super.c b/fs/adfs/super.c
index 06fdcc9..f137165 100644
--- a/fs/adfs/super.c
+++ b/fs/adfs/super.c
@@ -276,6 +276,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(adfs_inode_cachep);
}

diff --git a/fs/affs/super.c b/fs/affs/super.c
index 0782653..4fe18a8 100644
--- a/fs/affs/super.c
+++ b/fs/affs/super.c
@@ -129,6 +129,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(affs_inode_cachep);
}

diff --git a/fs/afs/super.c b/fs/afs/super.c
index f02b31e..af69050 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -123,6 +123,11 @@ void __exit afs_fs_exit(void)
BUG();
}

+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(afs_inode_cachep);
_leave("");
}
diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
index e18da23..02f3331 100644
--- a/fs/befs/linuxvfs.c
+++ b/fs/befs/linuxvfs.c
@@ -454,6 +454,11 @@ befs_init_inodecache(void)
static void
befs_destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(befs_inode_cachep);
}

diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
index 9870417..d5fc598 100644
--- a/fs/bfs/inode.c
+++ b/fs/bfs/inode.c
@@ -280,6 +280,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(bfs_inode_cachep);
}

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 2c8f7b2..010623a 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -106,6 +106,12 @@ void extent_io_exit(void)
list_del(&eb->leak_list);
kmem_cache_free(extent_buffer_cache, eb);
}
+
+ /*
+ * Make sure all delayed rcu free are flushed before we
+ * destroy caches.
+ */
+ rcu_barrier();
if (extent_state_cache)
kmem_cache_destroy(extent_state_cache);
if (extent_buffer_cache)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f6ab6f5..971d222 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6976,6 +6976,11 @@ static void init_once(void *foo)

void btrfs_destroy_cachep(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
if (btrfs_inode_cachep)
kmem_cache_destroy(btrfs_inode_cachep);
if (btrfs_trans_handle_cachep)
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index 1e67dd7..ecc251e 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -602,6 +602,11 @@ bad_cap:

static void destroy_caches(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ceph_inode_cachep);
kmem_cache_destroy(ceph_cap_cachep);
kmem_cache_destroy(ceph_dentry_cachep);
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 8b6e344..93ce9b3f 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -975,6 +975,11 @@ cifs_init_inodecache(void)
static void
cifs_destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(cifs_inode_cachep);
}

diff --git a/fs/coda/inode.c b/fs/coda/inode.c
index f181312..0c70460 100644
--- a/fs/coda/inode.c
+++ b/fs/coda/inode.c
@@ -85,6 +85,11 @@ int coda_init_inodecache(void)

void coda_destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(coda_inode_cachep);
}

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 6895493..f6acf8a 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -693,6 +693,12 @@ static void ecryptfs_free_kmem_caches(void)
{
int i;

+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
+
for (i = 0; i < ARRAY_SIZE(ecryptfs_cache_infos); i++) {
struct ecryptfs_cache_info *info;

diff --git a/fs/efs/super.c b/fs/efs/super.c
index e755ec7..2002431 100644
--- a/fs/efs/super.c
+++ b/fs/efs/super.c
@@ -96,6 +96,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(efs_inode_cachep);
}

diff --git a/fs/exofs/super.c b/fs/exofs/super.c
index 4337836..d271f96 100644
--- a/fs/exofs/super.c
+++ b/fs/exofs/super.c
@@ -206,6 +206,11 @@ static int init_inodecache(void)
*/
static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(exofs_inode_cachep);
}

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index b3621cb..de2051c 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -204,6 +204,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ext2_inode_cachep);
}

diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 8c3a44b..bd60e08 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -543,6 +543,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ext3_inode_cachep);
}

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index eb7aa3e..4e2aacb 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1046,6 +1046,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ext4_inode_cachep);
}

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index a3d81eb..35113bc 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -526,6 +526,11 @@ static int __init fat_init_inodecache(void)

static void __exit fat_destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(fat_inode_cachep);
}

diff --git a/fs/freevxfs/vxfs_super.c b/fs/freevxfs/vxfs_super.c
index d4fabd2..fed2c8a 100644
--- a/fs/freevxfs/vxfs_super.c
+++ b/fs/freevxfs/vxfs_super.c
@@ -279,6 +279,11 @@ static void __exit
vxfs_cleanup(void)
{
unregister_filesystem(&vxfs_fs_type);
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(vxfs_inode_cachep);
}

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 1cd6165..9078173 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1171,6 +1171,12 @@ static void fuse_fs_cleanup(void)
{
unregister_filesystem(&fuse_fs_type);
unregister_fuseblk();
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(fuse_inode_cachep);
}

diff --git a/fs/hfs/super.c b/fs/hfs/super.c
index 7b4c537..373a9e5 100644
--- a/fs/hfs/super.c
+++ b/fs/hfs/super.c
@@ -483,6 +483,12 @@ static int __init init_hfs_fs(void)
static void __exit exit_hfs_fs(void)
{
unregister_filesystem(&hfs_fs_type);
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(hfs_inode_cachep);
}

diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index a9bca4b..bde9ecf 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -615,6 +615,12 @@ static int __init init_hfsplus_fs(void)
static void __exit exit_hfsplus_fs(void)
{
unregister_filesystem(&hfsplus_fs_type);
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(hfsplus_inode_cachep);
}

diff --git a/fs/hpfs/super.c b/fs/hpfs/super.c
index 706a12c..3cb1da5 100644
--- a/fs/hpfs/super.c
+++ b/fs/hpfs/super.c
@@ -210,6 +210,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(hpfs_inode_cachep);
}

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index cc9281b..b482175 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -1042,6 +1042,11 @@ static int __init init_hugetlbfs_fs(void)

static void __exit exit_hugetlbfs_fs(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(hugetlbfs_inode_cachep);
kern_unmount(hugetlbfs_vfsmount);
unregister_filesystem(&hugetlbfs_fs_type);
diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c
index 29037c3..f94cde4 100644
--- a/fs/isofs/inode.c
+++ b/fs/isofs/inode.c
@@ -114,6 +114,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(isofs_inode_cachep);
}

diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
index 61ea413..ff48795 100644
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -418,6 +418,12 @@ static void __exit exit_jffs2_fs(void)
unregister_filesystem(&jffs2_fs_type);
jffs2_destroy_slab_caches();
jffs2_compressors_exit();
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(jffs2_inode_cachep);
}

diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 4a82950..2fc7602 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -898,6 +898,12 @@ static void __exit exit_jfs_fs(void)
jfs_proc_clean();
#endif
unregister_filesystem(&jfs_fs_type);
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(jfs_inode_cachep);
}

diff --git a/fs/logfs/inode.c b/fs/logfs/inode.c
index a422f42..3d1b9fa 100644
--- a/fs/logfs/inode.c
+++ b/fs/logfs/inode.c
@@ -401,5 +401,10 @@ int logfs_init_inode_cache(void)

void logfs_destroy_inode_cache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(logfs_inode_cache);
}
diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index 2a503ad..dc8d362 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -100,6 +100,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(minix_inode_cachep);
}

diff --git a/fs/ncpfs/inode.c b/fs/ncpfs/inode.c
index 333df07..0c62c55 100644
--- a/fs/ncpfs/inode.c
+++ b/fs/ncpfs/inode.c
@@ -89,6 +89,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ncp_inode_cachep);
}

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index e605d69..39aae2e 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1566,6 +1566,11 @@ static int __init nfs_init_inodecache(void)

static void nfs_destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(nfs_inode_cachep);
}

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 1099a76..956e5a4 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1386,6 +1386,12 @@ static void nilfs_segbuf_init_once(void *obj)

static void nilfs_destroy_cachep(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
+
if (nilfs_inode_cachep)
kmem_cache_destroy(nilfs_inode_cachep);
if (nilfs_transaction_cachep)
diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c
index b341492..ecc8625 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -3185,6 +3185,12 @@ static void __exit exit_ntfs_fs(void)
ntfs_debug("Unregistering NTFS driver.");

unregister_filesystem(&ntfs_fs_type);
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ntfs_big_inode_cache);
kmem_cache_destroy(ntfs_inode_cache);
kmem_cache_destroy(ntfs_name_cache);
diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index e31d6ae..6934459 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -691,6 +691,11 @@ static void __exit exit_dlmfs_fs(void)
flush_workqueue(user_dlm_worker);
destroy_workqueue(user_dlm_worker);

+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(dlmfs_inode_cache);

bdi_destroy(&dlmfs_backing_dev_info);
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 68f4541..0e91ec2 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -1818,6 +1818,11 @@ static int ocfs2_initialize_mem_caches(void)

static void ocfs2_free_mem_caches(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
if (ocfs2_inode_cachep)
kmem_cache_destroy(ocfs2_inode_cachep);
ocfs2_inode_cachep = NULL;
diff --git a/fs/openpromfs/inode.c b/fs/openpromfs/inode.c
index bc49c97..1b76370 100644
--- a/fs/openpromfs/inode.c
+++ b/fs/openpromfs/inode.c
@@ -463,6 +463,11 @@ static int __init init_openprom_fs(void)
static void __exit exit_openprom_fs(void)
{
unregister_filesystem(&openprom_fs_type);
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(op_inode_cachep);
}

diff --git a/fs/qnx4/inode.c b/fs/qnx4/inode.c
index 552e994..9534b4f 100644
--- a/fs/qnx4/inode.c
+++ b/fs/qnx4/inode.c
@@ -391,6 +391,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(qnx4_inode_cachep);
}

diff --git a/fs/qnx6/inode.c b/fs/qnx6/inode.c
index e44012d..3cba5d2 100644
--- a/fs/qnx6/inode.c
+++ b/fs/qnx6/inode.c
@@ -652,6 +652,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(qnx6_inode_cachep);
}

diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c
index 651ce76..ad39139 100644
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -603,6 +603,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(reiserfs_inode_cachep);
}

diff --git a/fs/romfs/super.c b/fs/romfs/super.c
index e64f6b5..f901eaf 100644
--- a/fs/romfs/super.c
+++ b/fs/romfs/super.c
@@ -648,6 +648,11 @@ error_register:
static void __exit exit_romfs_fs(void)
{
unregister_filesystem(&romfs_fs_type);
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(romfs_inode_cachep);
}

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 29cd014..260e392 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -425,6 +425,11 @@ static int __init init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(squashfs_inode_cachep);
}

diff --git a/fs/super.c b/fs/super.c
index cf00177..2d962aa 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -256,12 +256,6 @@ void deactivate_locked_super(struct super_block *s)

/* caches are now gone, we can safely kill the shrinker now */
unregister_shrinker(&s->s_shrink);
-
- /*
- * We need to call rcu_barrier so all the delayed rcu free
- * inodes are flushed before we release the fs module.
- */
- rcu_barrier();
put_filesystem(fs);
put_super(s);
} else {
diff --git a/fs/sysv/inode.c b/fs/sysv/inode.c
index 08d0b25..a08341c 100644
--- a/fs/sysv/inode.c
+++ b/fs/sysv/inode.c
@@ -376,5 +376,10 @@ int __init sysv_init_icache(void)

void sysv_destroy_icache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(sysv_inode_cachep);
}
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 5862dd9..e8ae748 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -2302,6 +2302,12 @@ static void __exit ubifs_exit(void)
dbg_debugfs_exit();
ubifs_compressors_exit();
unregister_shrinker(&ubifs_shrinker_info);
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ubifs_inode_slab);
unregister_filesystem(&ubifs_fs_type);
}
diff --git a/fs/udf/super.c b/fs/udf/super.c
index ac8a348..ebe9f52 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -170,6 +170,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(udf_inode_cachep);
}

diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index 302f340..f655c1d 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -1449,6 +1449,11 @@ static int init_inodecache(void)

static void destroy_inodecache(void)
{
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
kmem_cache_destroy(ufs_inode_cachep);
}

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 0d9de41..bbcbf2a 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1582,6 +1582,11 @@ xfs_init_zones(void)
STATIC void
xfs_destroy_zones(void)
{
+ /*
+ * Make sure all delayed rcu free are flushed before we
+ * destroy caches.
+ */
+ rcu_barrier();
kmem_zone_destroy(xfs_ili_zone);
kmem_zone_destroy(xfs_inode_zone);
kmem_zone_destroy(xfs_efi_zone);
--
1.7.10

2012-06-08 22:06:44

by Linus Torvalds

[permalink] [raw]

Subject: Re: [RFC, PATCH] fs: push rcu_barrier() from deactivate_locked_super() to filesystems

On Fri, Jun 8, 2012 at 3:00 PM, Kirill A. Shutemov
<[email protected]> wrote:
>
> IIUC, moving rcu_barrier() up should help, but I can't say that I fully
> understand SLAB_DESTROY_BY_RCU semantics.

.. hmm. I think you may be right. Even if we do move it up, we
probably shouldn't use it.

We don't even want SLAB_DESTROY_BY_RCU, since we do the delayed RCU
free for other reasons anyway, so it would duplicate the RCU delaying
and cause problems. I forgot about that little complication.

We could have a separate "RCU_BARRIER_ON_DESTROY" thing, but that's
just silly too.

Maybe your patch is the right thing.

Linus

2012-06-08 21:59:36

On Fri, Jun 08, 2012 at 03:31:20PM -0700, Andrew Morton wrote:
> On Fri, 8 Jun 2012 23:27:34 +0100
> Al Viro <[email protected]> wrote:
>
> > On Fri, Jun 08, 2012 at 03:25:50PM -0700, Andrew Morton wrote:
> >
> > > A neater implementation might be to add a kmem_cache* argument to
> > > unregister_filesystem(). If that is non-NULL, unregister_filesystem()
> > > does the rcu_barrier() and destroys the cache. That way we get to
> > > delete (rather than add) a bunch of code from all filesystems and new
> > > and out-of-tree filesystems cannot forget to perform the rcu_barrier().
> >
> > There's often enough more than one cache, so that one is no-go.
>
> kmem_cache** ;)
>
> Which filesystems have multiple inode caches?

Multiple inode caches? No.
Multiple caches with call_rcu() free? See btrfs or gfs2.

--
Kirill A. Shutemov

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2012-06-08 23:26:59

On Fri, Jun 08, 2012 at 03:02:53PM -0700, Andrew Morton wrote:
> On Sat, 9 Jun 2012 00:41:03 +0300
> "Kirill A. Shutemov" <[email protected]> wrote:
>
> > There's no reason to call rcu_barrier() on every deactivate_locked_super().
> > We only need to make sure that all delayed rcu free inodes are flushed
> > before we destroy related cache.
> >
> > Removing rcu_barrier() from deactivate_locked_super() affects some
> > fas paths. E.g. on my machine exit_group() of a last process in IPC
> > namespace takes 0.07538s. rcu_barrier() takes 0.05188s of that time.
>
> What an unpleasant patch. Is final-process-exiting-ipc-namespace a
> sufficiently high-frequency operation to justify the change?

> I don't really understand what's going on here. Are you saying that
> there is some filesystem against which we run deactivate_locked_super()
> during exit_group(), and that this filesystem doesn't use rcu-freeing
> of inodes? The description needs this level of detail, please.

I think the rcu_barrier() is in wrong place. We need it to safely destroy
inode cache. deactivate_locked_super() is part of umount() path, but all
filesystems I've checked have inode cache for whole filesystem, not
per-mount.

> The implementation would be less unpleasant if we could do the
> rcu_barrier() in kmem_cache_destroy(). I can't see a way of doing that
> without adding a dedicated slab flag, which would require editing all
> the filesystems anyway.

I think rcu_barrier() for all kmem_cache_destroy() would be too expensive.

> (kmem_cache_destroy() already has an rcu_barrier(). Can we do away
> with the private rcu games in the vfs and switch to
> SLAB_DESTROY_BY_RCU?)

--
Kirill A. Shutemov

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2012-06-11 09:14:47

by Kirill A. Shutemov

[permalink] [raw]

Subject: Re: [RFC, PATCH, RESEND] fs: push rcu_barrier() from deactivate_locked_super() to filesystems

On Sat, Jun 09, 2012 at 12:25:57AM -0700, Andrew Morton wrote:
> And... it seems that I misread what's going on. The individual
> filesystems are doing the rcu freeing of their inodes, so it is
> appropriate that they also call rcu_barrier() prior to running
> kmem_cache_free(). Which is what Kirill's patch does. oops.

Ack? ;)

--
Kirill A. Shutemov

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