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f03c65993b
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>
20 lines
400 B
C
20 lines
400 B
C
#ifndef _LINUX_PATH_H
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#define _LINUX_PATH_H
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struct dentry;
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struct vfsmount;
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struct path {
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struct vfsmount *mnt;
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struct dentry *dentry;
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};
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extern void path_get(struct path *);
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extern void path_put(struct path *);
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static inline int path_equal(const struct path *path1, const struct path *path2)
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{
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return path1->mnt == path2->mnt && path1->dentry == path2->dentry;
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}
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#endif /* _LINUX_PATH_H */
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