lookup_and_lock() combines locking the directory and performing a lookup prior to a change to the directory. Abstracting this prepares for changing the locking requirements. done_lookup_and_lock() provides the inverse of putting the dentry and unlocking. For "silly_rename" we will need to lookup_and_lock() in a directory that is already locked. For this purpose we add LOOKUP_PARENT_LOCKED. Like lookup_len_qstr(), lookup_and_lock() returns -ENOENT if LOOKUP_CREATE was NOT given and the name cannot be found,, and returns -EEXIST if LOOKUP_EXCL WAS given and the name CAN be found. These functions replace all uses of lookup_one_qstr() in namei.c except for those used for rename. The name might seem backwards as the lock happens before the lookup. A future patch will change this so that only a shared lock is taken before the lookup, and an exclusive lock on the dentry is taken after a successful lookup. So the order "lookup" then "lock" will make sense. This functionality is exported as lookup_and_lock_one() which takes a name and len rather than a qstr. Signed-off-by: NeilBrown <neilb@xxxxxxx> --- fs/namei.c | 102 ++++++++++++++++++++++++++++-------------- include/linux/namei.h | 15 ++++++- 2 files changed, 83 insertions(+), 34 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 69610047f6c6..3c0feca081a2 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1715,6 +1715,41 @@ struct dentry *lookup_one_qstr(const struct qstr *name, } EXPORT_SYMBOL(lookup_one_qstr); +static struct dentry *lookup_and_lock_nested(const struct qstr *last, + struct dentry *base, + unsigned int lookup_flags, + unsigned int subclass) +{ + struct dentry *dentry; + + if (!(lookup_flags & LOOKUP_PARENT_LOCKED)) + inode_lock_nested(base->d_inode, subclass); + + dentry = lookup_one_qstr(last, base, lookup_flags); + if (IS_ERR(dentry) && !(lookup_flags & LOOKUP_PARENT_LOCKED)) { + inode_unlock(base->d_inode); + } + return dentry; +} + +static struct dentry *lookup_and_lock(const struct qstr *last, + struct dentry *base, + unsigned int lookup_flags) +{ + return lookup_and_lock_nested(last, base, lookup_flags, + I_MUTEX_PARENT); +} + +void done_lookup_and_lock(struct dentry *base, struct dentry *dentry, + unsigned int lookup_flags) +{ + d_lookup_done(dentry); + dput(dentry); + if (!(lookup_flags & LOOKUP_PARENT_LOCKED)) + inode_unlock(base->d_inode); +} +EXPORT_SYMBOL(done_lookup_and_lock); + /** * lookup_fast - do fast lockless (but racy) lookup of a dentry * @nd: current nameidata @@ -2754,12 +2789,9 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct path_put(path); return ERR_PTR(-EINVAL); } - inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); - d = lookup_one_qstr(&last, path->dentry, 0); - if (IS_ERR(d)) { - inode_unlock(path->dentry->d_inode); + d = lookup_and_lock(&last, path->dentry, 0); + if (IS_ERR(d)) path_put(path); - } return d; } @@ -3053,6 +3085,22 @@ struct dentry *lookup_positive_unlocked(const char *name, } EXPORT_SYMBOL(lookup_positive_unlocked); +struct dentry *lookup_and_lock_one(struct mnt_idmap *idmap, + const char *name, int len, struct dentry *base, + unsigned int lookup_flags) +{ + struct qstr this; + int err; + + if (!idmap) + idmap = &nop_mnt_idmap; + err = lookup_one_common(idmap, name, base, len, &this); + if (err) + return ERR_PTR(err); + return lookup_and_lock(&this, base, lookup_flags); +} +EXPORT_SYMBOL(lookup_and_lock_one); + #ifdef CONFIG_UNIX98_PTYS int path_pts(struct path *path) { @@ -4071,7 +4119,6 @@ static struct dentry *filename_create(int dfd, struct filename *name, unsigned int reval_flag = lookup_flags & LOOKUP_REVAL; unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL; int type; - int err2; int error; error = filename_parentat(dfd, name, reval_flag, path, &last, &type); @@ -4083,36 +4130,30 @@ static struct dentry *filename_create(int dfd, struct filename *name, * (foo/., foo/.., /////) */ if (unlikely(type != LAST_NORM)) - goto out; + goto put; /* don't fail immediately if it's r/o, at least try to report other errors */ - err2 = mnt_want_write(path->mnt); + error = mnt_want_write(path->mnt); /* * Do the final lookup. Suppress 'create' if there is a trailing * '/', and a directory wasn't requested. */ if (last.name[last.len] && !want_dir) create_flags &= ~LOOKUP_CREATE; - inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); - dentry = lookup_one_qstr(&last, path->dentry, - reval_flag | create_flags); + dentry = lookup_and_lock(&last, path->dentry, reval_flag | create_flags); if (IS_ERR(dentry)) - goto unlock; + goto drop; - if (unlikely(err2)) { - error = err2; + if (unlikely(error)) goto fail; - } return dentry; fail: - d_lookup_done(dentry); - dput(dentry); + done_lookup_and_lock(path->dentry, dentry, reval_flag | create_flags); dentry = ERR_PTR(error); -unlock: - inode_unlock(path->dentry->d_inode); - if (!err2) +drop: + if (!error) mnt_drop_write(path->mnt); -out: +put: path_put(path); return dentry; } @@ -4130,14 +4171,13 @@ EXPORT_SYMBOL(kern_path_create); void done_path_create(struct path *path, struct dentry *dentry) { - dput(dentry); - inode_unlock(path->dentry->d_inode); + done_lookup_and_lock(path->dentry, dentry, LOOKUP_CREATE); mnt_drop_write(path->mnt); path_put(path); } EXPORT_SYMBOL(done_path_create); -inline struct dentry *user_path_create(int dfd, const char __user *pathname, +struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, unsigned int lookup_flags) { struct filename *filename = getname(pathname); @@ -4510,19 +4550,18 @@ int do_rmdir(int dfd, struct filename *name) if (error) goto exit2; - inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); - dentry = lookup_one_qstr(&last, path.dentry, lookup_flags); + dentry = lookup_and_lock(&last, path.dentry, lookup_flags); error = PTR_ERR(dentry); if (IS_ERR(dentry)) goto exit3; + error = security_path_rmdir(&path, dentry); if (error) goto exit4; error = vfs_rmdir(mnt_idmap(path.mnt), path.dentry->d_inode, dentry); exit4: - dput(dentry); + done_lookup_and_lock(path.dentry, dentry, lookup_flags); exit3: - inode_unlock(path.dentry->d_inode); mnt_drop_write(path.mnt); exit2: path_put(&path); @@ -4639,11 +4678,9 @@ int do_unlinkat(int dfd, struct filename *name) if (error) goto exit2; retry_deleg: - inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT); - dentry = lookup_one_qstr(&last, path.dentry, lookup_flags); + dentry = lookup_and_lock(&last, path.dentry, lookup_flags); error = PTR_ERR(dentry); if (!IS_ERR(dentry)) { - /* Why not before? Because we want correct error value */ if (last.name[last.len]) goto slashes; @@ -4655,9 +4692,8 @@ int do_unlinkat(int dfd, struct filename *name) error = vfs_unlink(mnt_idmap(path.mnt), path.dentry->d_inode, dentry, &delegated_inode); exit3: - dput(dentry); + done_lookup_and_lock(path.dentry, dentry, lookup_flags); } - inode_unlock(path.dentry->d_inode); if (inode) iput(inode); /* truncate the inode here */ inode = NULL; diff --git a/include/linux/namei.h b/include/linux/namei.h index 0d81e571a159..76c587a5ec3a 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -29,7 +29,11 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT}; #define LOOKUP_RCU BIT(8) /* RCU pathwalk mode; semi-internal */ #define LOOKUP_CACHED BIT(9) /* Only do cached lookup */ #define LOOKUP_PARENT BIT(10) /* Looking up final parent in path */ -/* 5 spare bits for pathwalk */ +#define LOOKUP_PARENT_LOCKED BIT(11) /* filesystem sets this for nested + * "lookup_and_lock_one" when it knows + * parent is sufficiently locked. + */ +/* 4 spare bits for pathwalk */ /* These tell filesystem methods that we are dealing with the final component... */ #define LOOKUP_OPEN BIT(16) /* ... in open */ @@ -82,6 +86,15 @@ struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap, const char *name, struct dentry *base, int len); +struct dentry *lookup_and_lock_one(struct mnt_idmap *idmap, + const char *name, int len, struct dentry *base, + unsigned int lookup_flags); +struct dentry *__lookup_and_lock_one(struct mnt_idmap *idmap, + const char *name, int len, struct dentry *base, + unsigned int lookup_flags); +void done_lookup_and_lock(struct dentry *base, struct dentry *dentry, + unsigned int lookup_flags); +void __done_lookup_and_lock(struct dentry *dentry); extern int follow_down_one(struct path *); extern int follow_down(struct path *path, unsigned int flags); -- 2.47.1