On Sun, 2023-11-19 at 20:17 -0500, Chuck Lever wrote: > From: Chuck Lever <chuck.lever@xxxxxxxxxx> > > Al Viro notes that normal system calls hold f_pos_lock when calling > ->iterate_shared and ->llseek; however nfsd_readdir() does not take > that mutex when calling these methods. > > It should be safe however because the struct file acquired by > nfsd_readdir() is not visible to other threads. > > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> > --- > fs/nfsd/vfs.c | 20 +++++++++++++++++--- > 1 file changed, 17 insertions(+), 3 deletions(-) > > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index fbbea7498f02..87a5953c6bf0 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -2109,9 +2109,23 @@ static __be32 nfsd_buffered_readdir(struct file *file, struct svc_fh *fhp, > return cdp->err; > } > > -/* > - * Read entries from a directory. > - * The NFSv3/4 verifier we ignore for now. > +/** > + * nfsd_readdir - Read entries from a directory > + * @rqstp: RPC transaction context > + * @fhp: NFS file handle of directory to be read > + * @offsetp: OUT: seek offset of final entry that was read > + * @cdp: OUT: an eof error value > + * @func: entry filler actor > + * > + * This implementation ignores the NFSv3/4 verifier cookie. > + * > + * NB: normal system calls hold file->f_pos_lock when calling > + * ->iterate_shared and ->llseek, but nfsd_readdir() does not. > + * Because the struct file acquired here is not visible to other > + * threads, it's internal state does not need mutex protection. > + * > + * Returns nfs_ok on success, otherwise an nfsstat code is > + * returned. > */ > __be32 > nfsd_readdir(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t *offsetp, > > Good thing to document Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
