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Abstracting this prepares for changing the locking requirements. done_lookup_and_lock() will be called by all callers of lookup_and_lock() to unlock and dput() 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. This is what callers want. These functions replace all uses of lookup_one_qstr_excl() 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 --- fs/namei.c | 118 ++++++++++++++++++++++-------------------- include/linux/namei.h | 3 ++ 2 files changed, 65 insertions(+), 56 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 29f86df4b9dc..371c80902c59 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1703,6 +1703,33 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name, } EXPORT_SYMBOL(lookup_one_qstr_excl); +static struct dentry *lookup_and_lock(const struct qstr *last, + struct dentry *base, + unsigned int lookup_flags) +{ + struct dentry *dentry; + int err; + + inode_lock_nested(base->d_inode, I_MUTEX_PARENT); + dentry = lookup_one_qstr_excl(last, base, lookup_flags); + if (IS_ERR(dentry)) + goto out; + err = -EEXIST; + if ((lookup_flags & LOOKUP_EXCL) && d_is_positive(dentry)) + goto err; + err = -ENOENT; + if (!(lookup_flags & LOOKUP_CREATE) && d_is_negative(dentry)) + goto err; + return dentry; + +err: + dput(dentry); + dentry = ERR_PTR(err); +out: + inode_unlock(base->d_inode); + return dentry; +} + /** * lookup_fast - do fast lockless (but racy) lookup of a dentry * @nd: current nameidata @@ -2741,16 +2768,9 @@ 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_excl(&last, path->dentry, 0); - if (!IS_ERR(d) && d_is_negative(d)) { - dput(d); - d = ERR_PTR(-ENOENT); - } - 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; } @@ -3051,6 +3071,22 @@ 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) { @@ -4080,7 +4116,6 @@ 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); @@ -4092,50 +4127,31 @@ 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 = 0; - inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); - dentry = lookup_one_qstr_excl(&last, path->dentry, - reval_flag | create_flags); + create_flags &= ~LOOKUP_CREATE; + dentry = lookup_and_lock(&last, path->dentry, reval_flag | create_flags); if (IS_ERR(dentry)) - goto unlock; + goto drop; - error = -EEXIST; - if (d_is_positive(dentry)) - goto fail; - - /* - * Special case - lookup gave negative, but... we had foo/bar/ - * From the vfs_mknod() POV we just have a negative dentry - - * all is fine. Let's be bastards - you had / on the end, you've - * been asking for (non-existent) directory. -ENOENT for you. - */ - if (unlikely(!create_flags)) { - error = -ENOENT; - goto fail; - } - 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); 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; } @@ -4555,23 +4571,18 @@ 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_excl(&last, path.dentry, lookup_flags); + dentry = lookup_and_lock(&last, path.dentry, lookup_flags); error = PTR_ERR(dentry); if (IS_ERR(dentry)) goto exit3; - if (!dentry->d_inode) { - error = -ENOENT; - goto exit4; - } + 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); exit3: - inode_unlock(path.dentry->d_inode); mnt_drop_write(path.mnt); exit2: path_put(&path); @@ -4691,13 +4702,11 @@ 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_excl(&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] || d_is_negative(dentry)) + if (last.name[last.len]) goto slashes; inode = dentry->d_inode; ihold(inode); @@ -4707,9 +4716,8 @@ 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); } - inode_unlock(path.dentry->d_inode); if (inode) iput(inode); /* truncate the inode here */ inode = NULL; @@ -4731,9 +4739,7 @@ int do_unlinkat(int dfd, struct filename *name) return error; slashes: - if (d_is_negative(dentry)) - error = -ENOENT; - else if (d_is_dir(dentry)) + if (d_is_dir(dentry)) error = -EISDIR; else error = -ENOTDIR; diff --git a/include/linux/namei.h b/include/linux/namei.h index 898fc8ba37e1..f882874a7b00 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -83,6 +83,9 @@ 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); extern int follow_down_one(struct path *); extern int follow_down(struct path *path, unsigned int flags);