bbddca8e8f
We need information about exports when crossing mountpoints during lookup or NFSv4 readdir. If we don't already have that information cached, we may have to ask (and wait for) rpc.mountd. In both cases we currently hold the i_mutex on the parent of the directory we're asking rpc.mountd about. We've seen situations where rpc.mountd performs some operation on that directory that tries to take the i_mutex again, resulting in deadlock. With some care, we may be able to avoid that in rpc.mountd. But it seems better just to avoid holding a mutex while waiting on userspace. It appears that lookup_one_len is pretty much the only operation that needs the i_mutex. So we could just drop the i_mutex elsewhere and do something like mutex_lock() lookup_one_len() mutex_unlock() In many cases though the lookup would have been cached and not required the i_mutex, so it's more efficient to create a lookup_one_len() variant that only takes the i_mutex when necessary. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
113 lines
3.3 KiB
C
113 lines
3.3 KiB
C
#ifndef _LINUX_NAMEI_H
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#define _LINUX_NAMEI_H
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#include <linux/kernel.h>
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#include <linux/path.h>
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#include <linux/fcntl.h>
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#include <linux/errno.h>
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enum { MAX_NESTED_LINKS = 8 };
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#define MAXSYMLINKS 40
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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 components" flag
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* - dentry cache is untrusted; force a real lookup
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* - suppress terminal automount
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*/
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#define LOOKUP_FOLLOW 0x0001
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#define LOOKUP_DIRECTORY 0x0002
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#define LOOKUP_AUTOMOUNT 0x0004
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#define LOOKUP_PARENT 0x0010
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#define LOOKUP_REVAL 0x0020
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#define LOOKUP_RCU 0x0040
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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_EXCL 0x0400
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#define LOOKUP_RENAME_TARGET 0x0800
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#define LOOKUP_JUMPED 0x1000
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#define LOOKUP_ROOT 0x2000
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#define LOOKUP_EMPTY 0x4000
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extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
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static inline int user_path_at(int dfd, const char __user *name, unsigned flags,
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struct path *path)
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{
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return user_path_at_empty(dfd, name, flags, path, NULL);
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}
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static inline int user_path(const char __user *name, struct path *path)
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{
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return user_path_at_empty(AT_FDCWD, name, LOOKUP_FOLLOW, path, NULL);
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}
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static inline int user_lpath(const char __user *name, struct path *path)
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{
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return user_path_at_empty(AT_FDCWD, name, 0, path, NULL);
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}
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static inline int user_path_dir(const char __user *name, struct path *path)
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{
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return user_path_at_empty(AT_FDCWD, name,
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LOOKUP_FOLLOW | LOOKUP_DIRECTORY, path, NULL);
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}
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extern int kern_path(const char *, unsigned, struct path *);
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extern struct dentry *kern_path_create(int, const char *, struct path *, unsigned int);
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extern struct dentry *user_path_create(int, const char __user *, struct path *, unsigned int);
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extern void done_path_create(struct path *, struct dentry *);
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extern struct dentry *kern_path_locked(const char *, struct path *);
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extern int kern_path_mountpoint(int, const char *, struct path *, unsigned int);
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extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
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extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
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extern int follow_down_one(struct path *);
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extern int follow_down(struct path *);
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extern int follow_up(struct path *);
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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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extern void nd_jump_link(struct path *path);
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static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
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{
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((char *) name)[min(len, maxlen)] = '\0';
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}
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/**
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* retry_estale - determine whether the caller should retry an operation
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* @error: the error that would currently be returned
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* @flags: flags being used for next lookup attempt
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*
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* Check to see if the error code was -ESTALE, and then determine whether
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* to retry the call based on whether "flags" already has LOOKUP_REVAL set.
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*
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* Returns true if the caller should try the operation again.
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*/
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static inline bool
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retry_estale(const long error, const unsigned int flags)
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{
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return error == -ESTALE && !(flags & LOOKUP_REVAL);
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}
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#endif /* _LINUX_NAMEI_H */
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