[PATCH v4 9/9] nilfs2: integrate sysfs support into driver

[Vyacheslav Dubeyko]

From: Vyacheslav Dubeyko <Vyacheslav.Dubeyko-***@public.gmane.org>
Subject: [PATCH v4 9/9] nilfs2: integrate sysfs support into driver

This patch integrates creation of sysfs groups and
attributes into NILFS file system driver.

It was found the issue with nilfs_sysfs_{create/delete}_snapshot_group
functions by Michael L. Semon <mlsemon35-***@public.gmane.org> in the first
version of the patch:

[ 4928.585682] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:579
[ 4928.585693] in_atomic(): 1, irqs_disabled(): 0, pid: 32676, name: umount.nilfs2
[ 4928.585698] 2 locks held by umount.nilfs2/32676:
[ 4928.585703] #0: (&type->s_umount_key#21){++++..}, at: [<790c18e2>] deactivate_super+0x37/0x58
[ 4928.585732] #1: (&(&nilfs->ns_cptree_lock)->rlock){+.+...}, at: [<791bf659>] nilfs_put_root+0x23/0x5a
[ 4928.585749] Preemption disabled at:[<791bf659>] nilfs_put_root+0x23/0x5a

[ 4928.585766] CPU: 0 PID: 32676 Comm: umount.nilfs2 Not tainted 3.14.0+ #2
[ 4928.585771] Hardware name: Dell Computer Corporation Dimension 2350/07W080, BIOS A01 12/17/2002
[ 4928.585777] 00000000 00000000 93cdddf8 793ff0bd c14dd780 93cdde20 7904bf38 794d5224
[ 4928.585795] 791bf659 791bf659 00007fa4 c14dda00 00000000 78025360 79552b80 93cdde68
[ 4928.585811] 7940136e 00000000 00000002 c14dd780 79552d10 c14ddc00 93cdde68 00000246
[ 4928.585828] Call Trace:
[ 4928.585842] [<793ff0bd>] dump_stack+0x4b/0x75
[ 4928.585854] [<7904bf38>] __might_sleep+0x111/0x16f
[ 4928.585862] [<791bf659>] ? nilfs_put_root+0x23/0x5a
[ 4928.585870] [<791bf659>] ? nilfs_put_root+0x23/0x5a
[ 4928.585880] [<7940136e>] mutex_lock_nested+0x1e/0x3ad
[ 4928.585893] [<7911186e>] ? sysfs_remove_dir+0x25/0x62
[ 4928.585901] [<7910fdb8>] kernfs_remove+0x12/0x26
[ 4928.585908] [<79111886>] sysfs_remove_dir+0x3d/0x62
[ 4928.585918] [<792953bb>] kobject_del+0x13/0x38
[ 4928.585926] [<791cabd4>] nilfs_sysfs_delete_snapshot_group+0xb/0xd
[ 4928.585934] [<791bf660>] nilfs_put_root+0x2a/0x5a
[ 4928.585942] [<791c3827>] nilfs_detach_log_writer+0x1ab/0x2c1
[ 4928.585953] [<7906c283>] ? call_rcu+0x17/0x19
[ 4928.585963] [<790d5c4b>] ? dispose_list+0x27/0x31
[ 4928.585973] [<791b4312>] nilfs_put_super+0x13/0x68
[ 4928.585980] [<790c1bc8>] generic_shutdown_super+0x60/0xd1
[ 4928.585988] [<790c29dd>] kill_block_super+0x1d/0x60
[ 4928.585996] [<790c188e>] deactivate_locked_super+0x22/0x3f
[ 4928.586096] [<790c18e9>] deactivate_super+0x3e/0x58
[ 4928.586107] [<790d95af>] mntput_no_expire+0xe2/0x141
[ 4928.586115] [<790d94db>] ? mntput_no_expire+0xe/0x141
[ 4928.586123] [<790dabed>] SyS_oldumount+0x70/0xa5
[ 4928.586131] [<794050ff>] syscall_call+0x7/0xb

The reason of the issue was placement of
nilfs_sysfs_{create/delete}_snapshot_group() call under
nilfs->ns_cptree_lock protection. But this protection is
unnecessary and wrong solution. The second version of the
patch fixes this issue.

Reported-by: Michael L. Semon <mlsemon35-***@public.gmane.org>
Signed-off-by: Vyacheslav Dubeyko <Vyacheslav.Dubeyko-***@public.gmane.org>
CC: Vyacheslav Dubeyko <slava-***@public.gmane.org>
CC: Ryusuke Konishi <konishi.ryusuke-***@public.gmane.org>
Tested-by: Michael L. Semon <mlsemon35-***@public.gmane.org>
---
fs/nilfs2/Makefile | 2 +-
fs/nilfs2/nilfs.h | 8 ++++++++
fs/nilfs2/super.c | 9 ++++++++-
fs/nilfs2/the_nilfs.c | 16 +++++++++++++++-
4 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/fs/nilfs2/Makefile b/fs/nilfs2/Makefile
index 85c9873..fc603e0 100644
--- a/fs/nilfs2/Makefile
+++ b/fs/nilfs2/Makefile
@@ -2,4 +2,4 @@ obj-$(CONFIG_NILFS2_FS) += nilfs2.o
nilfs2-y := inode.o file.o dir.o super.o namei.o page.o mdt.o \
btnode.o bmap.o btree.o direct.o dat.o recovery.o \
the_nilfs.o segbuf.o segment.o cpfile.o sufile.o \
- ifile.o alloc.o gcinode.o ioctl.o
+ ifile.o alloc.o gcinode.o ioctl.o sysfs.o
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 9bc72de..0696161 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -320,6 +320,14 @@ int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *);
int nilfs_init_gcinode(struct inode *inode);
void nilfs_remove_all_gcinodes(struct the_nilfs *nilfs);

+/* sysfs.c */
+int __init nilfs_sysfs_init(void);
+void nilfs_sysfs_exit(void);
+int nilfs_sysfs_create_device_group(struct super_block *);
+void nilfs_sysfs_delete_device_group(struct the_nilfs *);
+int nilfs_sysfs_create_snapshot_group(struct nilfs_root *);
+void nilfs_sysfs_delete_snapshot_group(struct nilfs_root *);
+
/*
* Inodes and files operations
*/
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 8c532b2..c519927 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1452,13 +1452,19 @@ static int __init init_nilfs_fs(void)
if (err)
goto fail;

- err = register_filesystem(&nilfs_fs_type);
+ err = nilfs_sysfs_init();
if (err)
goto free_cachep;

+ err = register_filesystem(&nilfs_fs_type);
+ if (err)
+ goto deinit_sysfs_entry;
+
printk(KERN_INFO "NILFS version 2 loaded\n");
return 0;

+deinit_sysfs_entry:
+ nilfs_sysfs_exit();
free_cachep:
nilfs_destroy_cachep();
fail:
@@ -1468,6 +1474,7 @@ fail:
static void __exit exit_nilfs_fs(void)
{
nilfs_destroy_cachep();
+ nilfs_sysfs_exit();
unregister_filesystem(&nilfs_fs_type);
}

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 59d5008..9da25fe 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -98,6 +98,7 @@ void destroy_nilfs(struct the_nilfs *nilfs)
{
might_sleep();
if (nilfs_init(nilfs)) {
+ nilfs_sysfs_delete_device_group(nilfs);
brelse(nilfs->ns_sbh[0]);
brelse(nilfs->ns_sbh[1]);
}
@@ -641,6 +642,10 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data)
if (err)
goto failed_sbh;

+ err = nilfs_sysfs_create_device_group(sb);
+ if (err)
+ goto failed_sbh;
+
set_nilfs_init(nilfs);
err = 0;
out:
@@ -741,12 +746,13 @@ nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
{
struct rb_node **p, *parent;
struct nilfs_root *root, *new;
+ int err;

root = nilfs_lookup_root(nilfs, cno);
if (root)
return root;

- new = kmalloc(sizeof(*root), GFP_KERNEL);
+ new = kzalloc(sizeof(*root), GFP_KERNEL);
if (!new)
return NULL;

@@ -783,6 +789,12 @@ nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)

spin_unlock(&nilfs->ns_cptree_lock);

+ err = nilfs_sysfs_create_snapshot_group(new);
+ if (err) {
+ kfree(new);
+ new = NULL;
+ }
+
return new;
}

@@ -791,6 +803,8 @@ void nilfs_put_root(struct nilfs_root *root)
if (atomic_dec_and_test(&root->count)) {
struct the_nilfs *nilfs = root->nilfs;

+ nilfs_sysfs_delete_snapshot_group(root);
+
spin_lock(&nilfs->ns_cptree_lock);
rb_erase(&root->rb_node, &nilfs->ns_cptree);
spin_unlock(&nilfs->ns_cptree_lock);