From: ebiederm@xmission.com (Eric W. Biederman)
To: Greg Kroah-Hartman <gregkh@suse.de>, Greg KH <greg@kroah.com>
Cc: Tejun Heo <htejun@gmail.com>,
Linux Containers <containers@lists.osdl.org>,
<netdev@vger.kernel.org>,
cornelia.huck@de.ibm.com, stern@rowland.harvard.edu,
kay.sievers@vrfy.org, <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
David Miller <davem@davemloft.net>
Subject: [PATCH 02/10] sysfs: Support for preventing unmounts.
Date: Sat, 01 Dec 2007 02:13:59 -0700 [thread overview]
Message-ID: <m1wsry7p60.fsf_-_@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <m11wa693t0.fsf@ebiederm.dsl.xmission.com> (Eric W. Biederman's message of "Sat, 01 Dec 2007 02:12:27 -0700")
To support mounting multiple instances of sysfs occassionally I
need to walk through all of the currently present sysfs super blocks.
To allow this iteration this patch adds sysfs_grab_supers and
sysfs_release_supers. While a piece of code is in a section
surrounded by these no more sysfs super blocks will be either created
or destroyed.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
fs/sysfs/mount.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++-----
fs/sysfs/sysfs.h | 10 +++++++
2 files changed, 81 insertions(+), 8 deletions(-)
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 7416826..ef5f7ae 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -41,47 +41,110 @@ struct sysfs_dirent sysfs_root = {
static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
{
- struct inode *inode;
- struct dentry *root;
+ struct sysfs_super_info *info = NULL;
+ struct inode *inode = NULL;
+ struct dentry *root = NULL;
+ int error;
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = SYSFS_MAGIC;
sb->s_op = &sysfs_ops;
sb->s_time_gran = 1;
- sysfs_sb = sb;
+ if (!sysfs_sb)
+ sysfs_sb = sb;
+
+ error = -ENOMEM;
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info)
+ goto out_err;
/* get root inode, initialize and unlock it */
+ error = -ENOMEM;
inode = sysfs_get_inode(&sysfs_root);
if (!inode) {
pr_debug("sysfs: could not get root inode\n");
- return -ENOMEM;
+ goto out_err;
}
/* instantiate and link root dentry */
+ error = -ENOMEM;
root = d_alloc_root(inode);
if (!root) {
pr_debug("%s: could not get root dentry!\n",__FUNCTION__);
- iput(inode);
- return -ENOMEM;
+ goto out_err;
}
root->d_fsdata = &sysfs_root;
sb->s_root = root;
+ sb->s_fs_info = info;
return 0;
+
+out_err:
+ dput(root);
+ iput(inode);
+ kfree(info);
+ if (sysfs_sb == sb)
+ sysfs_sb = NULL;
+ return error;
}
static int sysfs_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
- return get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
+ int rc;
+ mutex_lock(&sysfs_rename_mutex);
+ rc = get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
+ mutex_unlock(&sysfs_rename_mutex);
+ return rc;
}
-static struct file_system_type sysfs_fs_type = {
+struct file_system_type sysfs_fs_type = {
.name = "sysfs",
.get_sb = sysfs_get_sb,
.kill_sb = kill_anon_super,
};
+void sysfs_grab_supers(void)
+{
+ /* must hold sysfs_rename_mutex */
+ struct super_block *sb;
+ /* Loop until I have taken s_umount on all sysfs superblocks */
+restart:
+ spin_lock(&sb_lock);
+ list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+ if (sysfs_info(sb)->grabbed)
+ continue;
+ /* Wait for unmount activity to complete. */
+ if (sb->s_count < S_BIAS) {
+ sb->s_count += 1;
+ spin_unlock(&sb_lock);
+ down_read(&sb->s_umount);
+ drop_super(sb);
+ goto restart;
+ }
+ atomic_inc(&sb->s_active);
+ sysfs_info(sb)->grabbed = 1;
+ }
+ spin_unlock(&sb_lock);
+}
+
+void sysfs_release_supers(void)
+{
+ /* must hold sysfs_rename_mutex */
+ struct super_block *sb;
+restart:
+ spin_lock(&sb_lock);
+ list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+ if (!sysfs_info(sb)->grabbed)
+ continue;
+ sysfs_info(sb)->grabbed = 0;
+ spin_unlock(&sb_lock);
+ deactivate_super(sb);
+ goto restart;
+ }
+ spin_unlock(&sb_lock);
+}
+
int __init sysfs_init(void)
{
int err = -ENOMEM;
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index ff17f8d..3308759 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -85,12 +85,22 @@ struct sysfs_addrm_cxt {
int cnt;
};
+struct sysfs_super_info {
+ int grabbed;
+};
+
+#define sysfs_info(SB) ((struct sysfs_super_info *)(SB)->s_fs_info)
+
/*
* mount.c
*/
extern struct sysfs_dirent sysfs_root;
extern struct super_block *sysfs_sb;
extern struct kmem_cache *sysfs_dir_cachep;
+extern struct file_system_type sysfs_fs_type;
+
+void sysfs_grab_supers(void);
+void sysfs_release_supers(void);
/*
* dir.c
--
1.5.3.rc6.17.g1911
next prev parent reply other threads:[~2007-12-01 9:16 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-01 9:06 [PATCH 0/10] sysfs network namespace support Eric W. Biederman
2007-12-01 9:12 ` [PATCH 01/10] sysfs: Make sysfs_mount static again Eric W. Biederman
2007-12-01 9:13 ` Eric W. Biederman [this message]
2007-12-01 9:16 ` [PATCH 03/10] sysfs: sysfs_get_dentry add a sb parameter Eric W. Biederman
2007-12-01 9:18 ` [PATCH 04/10] sysfs: Implement __sysfs_get_dentry Eric W. Biederman
2007-12-01 9:23 ` [PATCH 05/10] sysfs: Rename Support multiple superblocks Eric W. Biederman
2007-12-01 9:25 ` [PATCH 06/10] sysfs: sysfs_chmod_file handle " Eric W. Biederman
2007-12-01 9:28 ` [PATCH 07/10] sysfs: Implement sysfs tagged directory support Eric W. Biederman
2007-12-01 9:30 ` [PATCH 08/10] sysfs: Implement sysfs_delete_link and sysfs_rename_link Eric W. Biederman
2007-12-01 9:33 ` [PATCH 09/10] driver core: Implement tagged directory support for device classes Eric W. Biederman
2007-12-01 9:35 ` [PATCH 10/10] net: Enable tagging for net_class directories in sysfs Eric W. Biederman
2007-12-01 13:10 ` namespace support requires network modules to say "GPL" Mark Lord
2007-12-01 13:13 ` Mark Lord
2007-12-01 19:17 ` Stephen Hemminger
2007-12-01 19:23 ` Alan Cox
2007-12-01 19:38 ` Stephen Hemminger
2007-12-01 19:45 ` Alan Cox
2007-12-01 20:13 ` Eric W. Biederman
2007-12-01 20:21 ` Mark Lord
2007-12-01 20:29 ` Arjan van de Ven
2007-12-01 22:12 ` Mark Lord
2007-12-01 23:13 ` Eric W. Biederman
2007-12-01 23:24 ` Jiri Slaby
2007-12-02 1:14 ` Eric W. Biederman
2007-12-01 23:51 ` Mark Lord
2007-12-02 1:08 ` Eric W. Biederman
2007-12-01 20:52 ` Eric W. Biederman
2007-12-01 22:13 ` Mark Lord
2007-12-03 0:02 ` David Schwartz
2007-12-03 0:14 ` Alan Cox
2007-12-01 19:54 ` Eric W. Biederman
2007-12-02 0:30 ` Stephen Hemminger
2007-12-02 2:02 ` Eric W. Biederman
2007-12-02 3:34 ` Mark Lord
2007-12-02 4:23 ` Stephen Hemminger
2007-12-02 19:28 ` Ben Greear
2007-12-02 20:03 ` Patrick McHardy
2007-12-02 20:43 ` Adrian Bunk
2007-12-02 21:59 ` Patrick McHardy
2007-12-03 1:14 ` Adrian Bunk
2007-12-03 8:33 ` Denis V. Lunev
2007-12-03 17:35 ` Eric W. Biederman
2007-12-03 18:19 ` Ben Greear
2007-12-03 18:57 ` Daniel Lezcano
2007-12-04 15:19 ` Daniel Lezcano
2007-12-04 18:03 ` Eric W. Biederman
2007-12-04 18:44 ` Ben Greear
2007-12-04 19:17 ` Eric W. Biederman
2007-12-04 19:35 ` Ben Greear
2007-12-04 20:09 ` Eric W. Biederman
2007-12-05 6:14 ` David Miller
2007-12-05 6:01 ` David Miller
2007-12-04 17:59 ` Eric W. Biederman
2007-12-04 18:57 ` Ben Greear
2007-12-04 20:01 ` Eric W. Biederman
2007-12-05 6:07 ` David Miller
2007-12-03 8:24 ` Romano Giannetti
2007-12-03 15:34 ` Arjan van de Ven
2007-12-03 18:03 ` Eric W. Biederman
2007-12-03 18:13 ` David Miller
2007-12-02 13:51 ` Alan Cox
2007-12-02 19:56 ` Valdis.Kletnieks
2007-12-21 3:07 ` [PATCH 0/10] sysfs network namespace support Greg KH
2007-12-21 13:04 ` Eric W. Biederman
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