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authorTejun Heo <tj@kernel.org>2019-11-04 15:54:30 -0800
committerTejun Heo <tj@kernel.org>2019-11-12 08:18:04 -0800
commit40430452fd5da1509177ac597b394614cd3a121f (patch)
tree0d1b300c769f24ac59de54981bb9e785b90a111b /include/linux/kernfs.h
parent33c5ac9175195c36a0b7005aaf503a2e81f117a1 (diff)
kernfs: use 64bit inos if ino_t is 64bit
Each kernfs_node is identified with a 64bit ID. The low 32bit is exposed as ino and the high gen. While this already allows using inos as keys by looking up with wildcard generation number of 0, it's adding unnecessary complications for 64bit ino archs which can directly use kernfs_node IDs as inos to uniquely identify each cgroup instance. This patch exposes IDs directly as inos on 64bit ino archs. The conversion is mostly straight-forward. * 32bit ino archs behave the same as before. 64bit ino archs now use the whole 64bit ID as ino and the generation number is fixed at 1. * 64bit inos still use the same idr allocator which gurantees that the lower 32bits identify the current live instance uniquely and the high 32bits are incremented whenever the low bits wrap. As the upper 32bits are no longer used as gen and we don't wanna start ino allocation with 33rd bit set, the initial value for highbits allocation is changed to 0 on 64bit ino archs. * blktrace exposes two 32bit numbers - (INO,GEN) pair - to identify the issuing cgroup. Userland builds FILEID_INO32_GEN fids from these numbers to look up the cgroups. To remain compatible with the behavior, always output (LOW32,HIGH32) which will be constructed back to the original 64bit ID by __kernfs_fh_to_dentry(). Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Namhyung Kim <namhyung@kernel.org>
Diffstat (limited to 'include/linux/kernfs.h')
-rw-r--r--include/linux/kernfs.h20
1 files changed, 14 insertions, 6 deletions
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 38267cc9420c..dded2e5a9f42 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -141,8 +141,8 @@ struct kernfs_node {
void *priv;
/*
- * 64bit unique ID. Lower 32bits carry the inode number and lower
- * generation.
+ * 64bit unique ID. On 64bit ino setups, id is the ino. On 32bit,
+ * the low 32bits are ino and upper generation.
*/
u64 id;
@@ -177,8 +177,8 @@ struct kernfs_root {
/* private fields, do not use outside kernfs proper */
struct idr ino_idr;
- u32 last_ino;
- u32 next_generation;
+ u32 last_id_lowbits;
+ u32 id_highbits;
struct kernfs_syscall_ops *syscall_ops;
/* list of kernfs_super_info of this root, protected by kernfs_mutex */
@@ -284,12 +284,20 @@ static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
static inline ino_t kernfs_id_ino(u64 id)
{
- return (u32)id;
+ /* id is ino if ino_t is 64bit; otherwise, low 32bits */
+ if (sizeof(ino_t) >= sizeof(u64))
+ return id;
+ else
+ return (u32)id;
}
static inline u32 kernfs_id_gen(u64 id)
{
- return id >> 32;
+ /* gen is fixed at 1 if ino_t is 64bit; otherwise, high 32bits */
+ if (sizeof(ino_t) >= sizeof(u64))
+ return 1;
+ else
+ return id >> 32;
}
static inline ino_t kernfs_ino(struct kernfs_node *kn)