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| author |   Al Viro <viro@zeniv.linux.org.uk> | 2011-01-14 22:30:21 -0500 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2011-01-16 13:47:07 -0500 |
| commit | f03c65993b98eeb909a4012ce7833c5857d74755 (patch) | |
| tree | a6dd5e353889b7fe4ab87c54170d09443d788fec /include | |
| parent | fix old umount_tree() breakage (diff) | |
| download | linux-dev-f03c65993b98eeb909a4012ce7833c5857d74755.tar.xz linux-dev-f03c65993b98eeb909a4012ce7833c5857d74755.zip | |
sanitize vfsmount refcounting changes
Instead of splitting refcount between (per-cpu) mnt_count
and (SMP-only) mnt_longrefs, make all references contribute
to mnt_count again and keep track of how many are longterm
ones.
Accounting rules for longterm count:
* 1 for each fs_struct.root.mnt
* 1 for each fs_struct.pwd.mnt
* 1 for having non-NULL ->mnt_ns
* decrement to 0 happens only under vfsmount lock exclusive
That allows nice common case for mntput() - since we can't drop the
final reference until after mnt_longterm has reached 0 due to the rules
above, mntput() can grab vfsmount lock shared and check mnt_longterm.
If it turns out to be non-zero (which is the common case), we know
that this is not the final mntput() and can just blindly decrement
percpu mnt_count. Otherwise we grab vfsmount lock exclusive and
do usual decrement-and-check of percpu mnt_count.
For fs_struct.c we have mnt_make_longterm() and mnt_make_shortterm();
namespace.c uses the latter in places where we don't already hold
vfsmount lock exclusive and opencodes a few remaining spots where
we need to manipulate mnt_longterm.
Note that we mostly revert the code outside of fs/namespace.c back
to what we used to have; in particular, normal code doesn't need
to care about two kinds of references, etc. And we get to keep
the optimization Nick's variant had bought us...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mount.h | 4 | ||||
| -rw-r--r-- | include/linux/path.h | 2 |
2 files changed, 1 insertions, 5 deletions
diff --git a/include/linux/mount.h b/include/linux/mount.h index af4765ea8fde..604f122a2326 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -60,7 +60,7 @@ struct vfsmount { struct super_block *mnt_sb; /* pointer to superblock */ #ifdef CONFIG_SMP struct mnt_pcp __percpu *mnt_pcp; - atomic_t mnt_longrefs; + atomic_t mnt_longterm; /* how many of the refs are longterm */ #else int mnt_count; int mnt_writers; @@ -96,8 +96,6 @@ extern int mnt_clone_write(struct vfsmount *mnt); extern void mnt_drop_write(struct vfsmount *mnt); extern void mntput(struct vfsmount *mnt); extern struct vfsmount *mntget(struct vfsmount *mnt); -extern void mntput_long(struct vfsmount *mnt); -extern struct vfsmount *mntget_long(struct vfsmount *mnt); extern void mnt_pin(struct vfsmount *mnt); extern void mnt_unpin(struct vfsmount *mnt); extern int __mnt_is_readonly(struct vfsmount *mnt); diff --git a/include/linux/path.h b/include/linux/path.h index a581e8c06533..edc98dec6266 100644 --- a/include/linux/path.h +++ b/include/linux/path.h @@ -10,9 +10,7 @@ struct path { }; extern void path_get(struct path *); -extern void path_get_long(struct path *); extern void path_put(struct path *); -extern void path_put_long(struct path *); static inline int path_equal(const struct path *path1, const struct path *path2) { |