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new helper: lookup_positive_unlocked()

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Most of the callers of lookup_one_len_unlocked() treat negatives are
ERR_PTR(-ENOENT).  Provide a helper that would do just that.  Note
that a pinned positive dentry remains positive - it's ->d_inode is
stable, etc.; a pinned _negative_ dentry can become positive at any
point as long as you are not holding its parent at least shared.
So using lookup_one_len_unlocked() needs to be careful;
lookup_positive_unlocked() is safer and that's what the callers
end up open-coding anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2019-10-31 01:21:58 -04:00
parent d41efb522e
commit 6c2d4798a8
9 changed files with 35 additions and 47 deletions
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fs/debugfs/inode.c
+1 -5
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@@ -299,13 +299,9 @@ struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
if (!parent)
parent = debugfs_mount->mnt_root;
dentry = lookup_one_len_unlocked(name, parent, strlen(name));
dentry = lookup_positive_unlocked(name, parent, strlen(name));
if (IS_ERR(dentry))
return NULL;
if (!d_really_is_positive(dentry)) {
dput(dentry);
return NULL;
}
return dentry;
}
EXPORT_SYMBOL_GPL(debugfs_lookup);