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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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5590ff0d55
Here is a series of patches which introduce in total 13 new system calls which take a file descriptor/filename pair instead of a single file name. These functions, openat etc, have been discussed on numerous occasions. They are needed to implement race-free filesystem traversal, they are necessary to implement a virtual per-thread current working directory (think multi-threaded backup software), etc. We have in glibc today implementations of the interfaces which use the /proc/self/fd magic. But this code is rather expensive. Here are some results (similar to what Jim Meyering posted before). The test creates a deep directory hierarchy on a tmpfs filesystem. Then rm -fr is used to remove all directories. Without syscall support I get this: real 0m31.921s user 0m0.688s sys 0m31.234s With syscall support the results are much better: real 0m20.699s user 0m0.536s sys 0m20.149s The interfaces are for obvious reasons currently not much used. But they'll be used. coreutils (and Jeff's posixutils) are already using them. Furthermore, code like ftw/fts in libc (maybe even glob) will also start using them. I expect a patch to make follow soon. Every program which is walking the filesystem tree will benefit. Signed-off-by: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@ftp.linux.org.uk> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
97 lines
2.9 KiB
C
97 lines
2.9 KiB
C
#ifndef _LINUX_NAMEI_H
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#define _LINUX_NAMEI_H
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#include <linux/linkage.h>
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struct vfsmount;
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struct open_intent {
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int flags;
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int create_mode;
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struct file *file;
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};
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enum { MAX_NESTED_LINKS = 5 };
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struct nameidata {
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struct dentry *dentry;
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struct vfsmount *mnt;
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struct qstr last;
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unsigned int flags;
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int last_type;
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unsigned depth;
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char *saved_names[MAX_NESTED_LINKS + 1];
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/* Intent data */
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union {
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struct open_intent open;
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} intent;
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};
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/*
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* Type of the last component on LOOKUP_PARENT
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*/
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enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
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/*
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* The bitmask for a lookup event:
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* - follow links at the end
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* - require a directory
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* - ending slashes ok even for nonexistent files
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* - internal "there are more path compnents" flag
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* - locked when lookup done with dcache_lock held
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* - dentry cache is untrusted; force a real lookup
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*/
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#define LOOKUP_FOLLOW 1
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#define LOOKUP_DIRECTORY 2
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#define LOOKUP_CONTINUE 4
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#define LOOKUP_PARENT 16
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#define LOOKUP_NOALT 32
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#define LOOKUP_REVAL 64
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/*
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* Intent data
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*/
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#define LOOKUP_OPEN (0x0100)
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#define LOOKUP_CREATE (0x0200)
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#define LOOKUP_ACCESS (0x0400)
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extern int FASTCALL(__user_walk(const char __user *, unsigned, struct nameidata *));
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extern int FASTCALL(__user_walk_fd(int dfd, const char __user *, unsigned, struct nameidata *));
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#define user_path_walk(name,nd) \
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__user_walk_fd(AT_FDCWD, name, LOOKUP_FOLLOW, nd)
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#define user_path_walk_link(name,nd) \
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__user_walk_fd(AT_FDCWD, name, 0, nd)
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extern int FASTCALL(path_lookup(const char *, unsigned, struct nameidata *));
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extern int FASTCALL(path_walk(const char *, struct nameidata *));
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extern int FASTCALL(link_path_walk(const char *, struct nameidata *));
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extern void path_release(struct nameidata *);
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extern void path_release_on_umount(struct nameidata *);
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extern int __user_path_lookup_open(const char __user *, unsigned lookup_flags, struct nameidata *nd, int open_flags);
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extern int path_lookup_open(int dfd, const char *name, unsigned lookup_flags, struct nameidata *, int open_flags);
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extern struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
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int (*open)(struct inode *, struct file *));
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extern struct file *nameidata_to_filp(struct nameidata *nd, int flags);
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extern void release_open_intent(struct nameidata *);
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extern struct dentry * lookup_one_len(const char *, struct dentry *, int);
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extern __deprecated_for_modules struct dentry * lookup_hash(struct nameidata *);
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extern int follow_down(struct vfsmount **, struct dentry **);
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extern int follow_up(struct vfsmount **, struct dentry **);
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extern struct dentry *lock_rename(struct dentry *, struct dentry *);
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extern void unlock_rename(struct dentry *, struct dentry *);
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static inline void nd_set_link(struct nameidata *nd, char *path)
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{
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nd->saved_names[nd->depth] = path;
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}
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static inline char *nd_get_link(struct nameidata *nd)
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{
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return nd->saved_names[nd->depth];
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}
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#endif /* _LINUX_NAMEI_H */
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