From a4f5b52167a80edec74093fe6fef291a0318f4ba Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 3 Jul 2022 22:07:32 -0400 Subject: step_into(): lose inode argument make handle_mounts() always fetch it. This is just the first step - the callers of step_into() will stop trying to calculate the sucker, etc. The passed value should be equal to dentry->d_inode in all cases; in RCU mode - fetched after we'd sampled ->d_seq. Might as well fetch it here. We do need to validate ->d_seq, which duplicates the check currently done in lookup_fast(); that duplication will go away shortly. After that change handle_mounts() always ignores the initial value of *inode and always sets it on success. Signed-off-by: Al Viro --- fs/namei.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 8dd7874816cc..60e17152374a 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1536,6 +1536,9 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, path->dentry = dentry; if (nd->flags & LOOKUP_RCU) { unsigned int seq = nd->next_seq; + *inode = dentry->d_inode; + if (read_seqcount_retry(&dentry->d_seq, seq)) + return -ECHILD; if (unlikely(!*inode)) return -ENOENT; if (likely(__follow_mount_rcu(nd, path, inode))) @@ -1848,9 +1851,10 @@ all_done: // pure jump * NOTE: dentry must be what nd->next_seq had been sampled from. */ static const char *step_into(struct nameidata *nd, int flags, - struct dentry *dentry, struct inode *inode) + struct dentry *dentry) { struct path path; + struct inode *inode; int err = handle_mounts(nd, dentry, &path, &inode); if (err < 0) @@ -1976,7 +1980,7 @@ static const char *handle_dots(struct nameidata *nd, int type) parent = follow_dotdot(nd, &inode); if (IS_ERR(parent)) return ERR_CAST(parent); - error = step_into(nd, WALK_NOFOLLOW, parent, inode); + error = step_into(nd, WALK_NOFOLLOW, parent); if (unlikely(error)) return error; @@ -2021,7 +2025,7 @@ static const char *walk_component(struct nameidata *nd, int flags) } if (!(flags & WALK_MORE) && nd->depth) put_link(nd); - return step_into(nd, flags, dentry, inode); + return step_into(nd, flags, dentry); } /* @@ -2480,8 +2484,7 @@ static int handle_lookup_down(struct nameidata *nd) if (!(nd->flags & LOOKUP_RCU)) dget(nd->path.dentry); nd->next_seq = nd->seq; - return PTR_ERR(step_into(nd, WALK_NOFOLLOW, - nd->path.dentry, nd->inode)); + return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry)); } /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ @@ -3470,7 +3473,7 @@ static const char *open_last_lookups(struct nameidata *nd, finish_lookup: if (nd->depth) put_link(nd); - res = step_into(nd, WALK_TRAILING, dentry, inode); + res = step_into(nd, WALK_TRAILING, dentry); if (unlikely(res)) nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); return res; -- cgit v1.2.3