From: Miklos Szeredi Add a unique ID to each vfsmount using the IDR infrastructure. The identifiers are reused after the vfsmount is freed. Signed-off-by: Miklos Szeredi --- fs/namespace.c | 34 ++++++++++++++++++++++++++++++++++ include/linux/mount.h | 1 + 2 files changed, 35 insertions(+) Index: vfs-2.6/fs/namespace.c =================================================================== --- vfs-2.6.orig/fs/namespace.c 2008-03-26 21:37:06.000000000 +0100 +++ vfs-2.6/fs/namespace.c 2008-03-26 21:37:40.000000000 +0100 @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include "pnode.h" @@ -39,6 +40,7 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); static int event; +static DEFINE_IDA(mnt_id_ida); static struct list_head *mount_hashtable __read_mostly; static struct kmem_cache *mnt_cache __read_mostly; @@ -58,10 +60,41 @@ static inline unsigned long hash(struct #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) +static int mnt_alloc_id(struct vfsmount *mnt) +{ + int res; + + retry: + spin_lock(&vfsmount_lock); + res = ida_get_new(&mnt_id_ida, &mnt->mnt_id); + spin_unlock(&vfsmount_lock); + if (res == -EAGAIN) { + if (ida_pre_get(&mnt_id_ida, GFP_KERNEL)) + goto retry; + res = -ENOMEM; + } + return res; +} + +static void mnt_free_id(struct vfsmount *mnt) +{ + spin_lock(&vfsmount_lock); + ida_remove(&mnt_id_ida, mnt->mnt_id); + spin_unlock(&vfsmount_lock); +} + struct vfsmount *alloc_vfsmnt(const char *name) { struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); if (mnt) { + int err; + + err = mnt_alloc_id(mnt); + if (err) { + kmem_cache_free(mnt_cache, mnt); + return NULL; + } + atomic_set(&mnt->mnt_count, 1); INIT_LIST_HEAD(&mnt->mnt_hash); INIT_LIST_HEAD(&mnt->mnt_child); @@ -353,6 +386,7 @@ EXPORT_SYMBOL(simple_set_mnt); void free_vfsmnt(struct vfsmount *mnt) { kfree(mnt->mnt_devname); + mnt_free_id(mnt); kmem_cache_free(mnt_cache, mnt); } Index: vfs-2.6/include/linux/mount.h =================================================================== --- vfs-2.6.orig/include/linux/mount.h 2008-03-26 21:37:06.000000000 +0100 +++ vfs-2.6/include/linux/mount.h 2008-03-26 21:37:40.000000000 +0100 @@ -56,6 +56,7 @@ struct vfsmount { struct list_head mnt_slave; /* slave list entry */ struct vfsmount *mnt_master; /* slave is on master->mnt_slave_list */ struct mnt_namespace *mnt_ns; /* containing namespace */ + int mnt_id; /* mount identifier */ /* * We put mnt_count & mnt_expiry_mark at the end of struct vfsmount * to let these frequently modified fields in a separate cache line -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/