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new helper: lookup_positive_unlocked()

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[ Upstream commit 6c2d4798a8d16cf4f3a28c3cd4af4f1dcbbb4d04 ]

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>
Stable-dep-of: 0d5a4f8f775f ("fs: Fix error checking for d_hash_and_lookup()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Al Viro
2019-10-31 01:21:58 -04:00
committed by Greg Kroah-Hartman
parent 5701502619
commit 3c70569e17
9 changed files with 35 additions and 48 deletions
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4
fs/nfsd/nfs3xdr.c
View File

@@ -855,13 +855,11 @@ compose_entry_fh(struct nfsd3_readdirres *cd, struct svc_fh *fhp,
} else
dchild = dget(dparent);
} else
dchild = lookup_one_len_unlocked(name, dparent, namlen);
dchild = lookup_positive_unlocked(name, dparent, namlen);
if (IS_ERR(dchild))
return rv;
if (d_mountpoint(dchild))
goto out;
if (d_really_is_negative(dchild))
goto out;
if (dchild->d_inode->i_ino != ino)
goto out;
rv = fh_compose(fhp, exp, dchild, &cd->fh);

11
fs/nfsd/nfs4xdr.c
View File

@@ -2984,18 +2984,9 @@ nfsd4_encode_dirent_fattr(struct xdr_stream *xdr, struct nfsd4_readdir *cd,
__be32 nfserr;
int ignore_crossmnt = 0;
dentry = lookup_one_len_unlocked(name, cd->rd_fhp->fh_dentry, namlen);
dentry = lookup_positive_unlocked(name, cd->rd_fhp->fh_dentry, namlen);
if (IS_ERR(dentry))
return nfserrno(PTR_ERR(dentry));
if (d_really_is_negative(dentry)) {
/*
* we're not holding the i_mutex here, so there's
* a window where this directory entry could have gone
* away.
*/
dput(dentry);
return nfserr_noent;
}
exp_get(exp);
/*