2a4419b5b2
fs: fs_struct rwlock to spinlock struct fs_struct.lock is an rwlock with the read-side used to protect root and pwd members while taking references to them. Taking a reference to a path typically requires just 2 atomic ops, so the critical section is very small. Parallel read-side operations would have cacheline contention on the lock, the dentry, and the vfsmount cachelines, so the rwlock is unlikely to ever give a real parallelism increase. Replace it with a spinlock to avoid one or two atomic operations in typical path lookup fastpath. Signed-off-by: Nick Piggin <npiggin@kernel.dk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
52 lines
1.1 KiB
C
52 lines
1.1 KiB
C
#ifndef _LINUX_FS_STRUCT_H
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#define _LINUX_FS_STRUCT_H
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#include <linux/path.h>
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struct fs_struct {
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int users;
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spinlock_t lock;
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int umask;
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int in_exec;
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struct path root, pwd;
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};
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extern struct kmem_cache *fs_cachep;
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extern void exit_fs(struct task_struct *);
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extern void set_fs_root(struct fs_struct *, struct path *);
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extern void set_fs_pwd(struct fs_struct *, struct path *);
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extern struct fs_struct *copy_fs_struct(struct fs_struct *);
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extern void free_fs_struct(struct fs_struct *);
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extern void daemonize_fs_struct(void);
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extern int unshare_fs_struct(void);
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static inline void get_fs_root(struct fs_struct *fs, struct path *root)
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{
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spin_lock(&fs->lock);
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*root = fs->root;
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path_get(root);
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spin_unlock(&fs->lock);
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}
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static inline void get_fs_pwd(struct fs_struct *fs, struct path *pwd)
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{
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spin_lock(&fs->lock);
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*pwd = fs->pwd;
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path_get(pwd);
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spin_unlock(&fs->lock);
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}
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static inline void get_fs_root_and_pwd(struct fs_struct *fs, struct path *root,
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struct path *pwd)
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{
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spin_lock(&fs->lock);
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*root = fs->root;
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path_get(root);
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*pwd = fs->pwd;
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path_get(pwd);
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spin_unlock(&fs->lock);
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}
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#endif /* _LINUX_FS_STRUCT_H */
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