From 5b6ca027d85b7438c84b78a54ccdc2e53f2909cd Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 9 Mar 2011 23:04:47 -0500 Subject: reduce vfs_path_lookup() to do_path_lookup() New lookup flag: LOOKUP_ROOT. nd->root is set (and held) by caller, path_init() starts walking from that place and all pathname resolution machinery never drops nd->root if that flag is set. That turns vfs_path_lookup() into a special case of do_path_lookup() *and* gets us down to 3 callers of link_path_walk(), making it finally feasible to rip the handling of trailing symlink out of link_path_walk(). That will not only simply the living hell out of it, but make life much simpler for unionfs merge. Trailing symlink handling will become iterative, which is a good thing for stack footprint in a lot of situations as well. Signed-off-by: Al Viro --- fs/namei.c | 95 ++++++++++++++++++++++++++++---------------------------------- 1 file changed, 43 insertions(+), 52 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 0bebd13e5cb7..8ee7785d5642 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -401,9 +401,11 @@ static int nameidata_drop_rcu(struct nameidata *nd) { struct fs_struct *fs = current->fs; struct dentry *dentry = nd->path.dentry; + int want_root = 0; BUG_ON(!(nd->flags & LOOKUP_RCU)); - if (nd->root.mnt) { + if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { + want_root = 1; spin_lock(&fs->lock); if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry) @@ -414,7 +416,7 @@ static int nameidata_drop_rcu(struct nameidata *nd) goto err; BUG_ON(nd->inode != dentry->d_inode); spin_unlock(&dentry->d_lock); - if (nd->root.mnt) { + if (want_root) { path_get(&nd->root); spin_unlock(&fs->lock); } @@ -427,7 +429,7 @@ static int nameidata_drop_rcu(struct nameidata *nd) err: spin_unlock(&dentry->d_lock); err_root: - if (nd->root.mnt) + if (want_root) spin_unlock(&fs->lock); return -ECHILD; } @@ -454,9 +456,11 @@ static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry { struct fs_struct *fs = current->fs; struct dentry *parent = nd->path.dentry; + int want_root = 0; BUG_ON(!(nd->flags & LOOKUP_RCU)); - if (nd->root.mnt) { + if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { + want_root = 1; spin_lock(&fs->lock); if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry) @@ -476,7 +480,7 @@ static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry parent->d_count++; spin_unlock(&dentry->d_lock); spin_unlock(&parent->d_lock); - if (nd->root.mnt) { + if (want_root) { path_get(&nd->root); spin_unlock(&fs->lock); } @@ -490,7 +494,7 @@ err: spin_unlock(&dentry->d_lock); spin_unlock(&parent->d_lock); err_root: - if (nd->root.mnt) + if (want_root) spin_unlock(&fs->lock); return -ECHILD; } @@ -501,7 +505,8 @@ static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata *nd, struct d if (nd->flags & LOOKUP_RCU) { if (unlikely(nameidata_dentry_drop_rcu(nd, dentry))) { nd->flags &= ~LOOKUP_RCU; - nd->root.mnt = NULL; + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; rcu_read_unlock(); br_read_unlock(vfsmount_lock); return -ECHILD; @@ -525,7 +530,8 @@ static int nameidata_drop_rcu_last(struct nameidata *nd) BUG_ON(!(nd->flags & LOOKUP_RCU)); nd->flags &= ~LOOKUP_RCU; - nd->root.mnt = NULL; + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; spin_lock(&dentry->d_lock); if (!__d_rcu_to_refcount(dentry, nd->seq)) goto err_unlock; @@ -1053,7 +1059,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) failed: nd->flags &= ~LOOKUP_RCU; - nd->root.mnt = NULL; + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; rcu_read_unlock(); br_read_unlock(vfsmount_lock); return -ECHILD; @@ -1310,7 +1317,8 @@ static void terminate_walk(struct nameidata *nd) path_put(&nd->path); } else { nd->flags &= ~LOOKUP_RCU; - nd->root.mnt = NULL; + if (!(nd->flags & LOOKUP_ROOT)) + nd->root.mnt = NULL; rcu_read_unlock(); br_read_unlock(vfsmount_lock); } @@ -1477,6 +1485,25 @@ static int path_init(int dfd, const char *name, unsigned int flags, nd->last_type = LAST_ROOT; /* if there are only slashes... */ nd->flags = flags | LOOKUP_JUMPED; nd->depth = 0; + if (flags & LOOKUP_ROOT) { + struct inode *inode = nd->root.dentry->d_inode; + if (!inode->i_op->lookup) + return -ENOTDIR; + retval = inode_permission(inode, MAY_EXEC); + if (retval) + return retval; + nd->path = nd->root; + nd->inode = inode; + if (flags & LOOKUP_RCU) { + br_read_lock(vfsmount_lock); + rcu_read_lock(); + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); + } else { + path_get(&nd->path); + } + return 0; + } + nd->root.mnt = NULL; if (*name=='/') { @@ -1587,7 +1614,7 @@ static int path_lookupat(int dfd, const char *name, if (base) fput(base); - if (nd->root.mnt) { + if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { path_put(&nd->root); nd->root.mnt = NULL; } @@ -1638,46 +1665,10 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, const char *name, unsigned int flags, struct nameidata *nd) { - int result; - - /* same as do_path_lookup */ - nd->last_type = LAST_ROOT; - nd->flags = flags | LOOKUP_JUMPED; - nd->depth = 0; - - nd->path.dentry = dentry; - nd->path.mnt = mnt; - path_get(&nd->path); - nd->root = nd->path; - path_get(&nd->root); - nd->inode = nd->path.dentry->d_inode; - - current->total_link_count = 0; - - result = link_path_walk(name, nd); - if (!result) - result = handle_reval_path(nd); - if (result == -ESTALE) { - /* nd->path had been dropped */ - current->total_link_count = 0; - nd->path.dentry = dentry; - nd->path.mnt = mnt; - nd->inode = dentry->d_inode; - path_get(&nd->path); - nd->flags = flags | LOOKUP_JUMPED | LOOKUP_REVAL; - - result = link_path_walk(name, nd); - if (!result) - result = handle_reval_path(nd); - } - if (unlikely(!result && !audit_dummy_context() && nd->path.dentry && - nd->inode)) - audit_inode(name, nd->path.dentry); - - path_put(&nd->root); - nd->root.mnt = NULL; - - return result; + nd->root.dentry = dentry; + nd->root.mnt = mnt; + /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */ + return do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, nd); } static struct dentry *__lookup_hash(struct qstr *name, @@ -2320,7 +2311,7 @@ static struct file *path_openat(int dfd, const char *pathname, path_put(&link); } out: - if (nd.root.mnt) + if (nd.root.mnt && !(nd.flags & LOOKUP_ROOT)) path_put(&nd.root); if (base) fput(base); -- cgit v1.2.3-59-g8ed1b