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step_into(): lose inode argument

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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 <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2022-07-03 22:07:32 -04:00
parent 03fa86e9f7
commit a4f5b52167
1 changed files with 9 additions and 6 deletions
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15
fs/namei.c
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@ -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;