On Fri, May 14, 2021 at 03:46:57PM +0000, Trond Myklebust wrote: > On Fri, 2021-05-14 at 11:58 +0800, Nick Huang wrote: > > From: Yu Hsiang Huang <nickhuang@xxxxxxxxxxxx> > > > > Truncation of an unlinked inode may take a long time for I/O waiting, > > and > > it doesn't have to prevent access to the directory. Thus, let > > truncation > > occur outside the directory's mutex, just like do_unlinkat() does. > > > > Signed-off-by: Yu Hsiang Huang <nickhuang@xxxxxxxxxxxx> > > Signed-off-by: Bing Jing Chang <bingjingc@xxxxxxxxxxxx> > > Signed-off-by: Robbie Ko <robbieko@xxxxxxxxxxxx> > > --- > > fs/nfsd/vfs.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > > index 15adf1f6ab21..39948f130712 100644 > > --- a/fs/nfsd/vfs.c > > +++ b/fs/nfsd/vfs.c > > @@ -1859,6 +1859,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct > > svc_fh *fhp, int type, > > { > > struct dentry *dentry, *rdentry; > > struct inode *dirp; > > + struct inode *rinode; > > __be32 err; > > int host_err; > > > > @@ -1887,6 +1888,8 @@ nfsd_unlink(struct svc_rqst *rqstp, struct > > svc_fh *fhp, int type, > > host_err = -ENOENT; > > goto out_drop_write; > > } > > + rinode = d_inode(rdentry); > > + ihold(rinode); > > > > if (!type) > > type = d_inode(rdentry)->i_mode & S_IFMT; > > @@ -1902,6 +1905,8 @@ nfsd_unlink(struct svc_rqst *rqstp, struct > > svc_fh *fhp, int type, > > if (!host_err) > > host_err = commit_metadata(fhp); > > Why leave the commit_metadata() call under the lock? If you're > concerned about latency, then it makes more sense to call fh_unlock() > before flushing those metadata updates to disk. > > This is, BTW, an optimisation that appears to be possible in several > other cases in fs/nfsd/vfs.c. I'm tentatively applying the original patch plus the following. Create and rename code are two other places where we have commit_metadata() calls that could probably be moved out from under locks but they looked slightly more complicated. --b. commit ec79990df716 Author: J. Bruce Fields <bfields@xxxxxxxxxx> Date: Fri May 14 18:21:37 2021 -0400 nfsd: move some commit_metadata()s outside the inode lock The commit may be time-consuming and there's no need to hold the lock for it. More of these are possible, these were just some easy ones. Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 39948f130712..d73d3c9126fc 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1613,9 +1613,9 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp, host_err = vfs_symlink(&init_user_ns, d_inode(dentry), dnew, path); err = nfserrno(host_err); + fh_unlock(fhp); if (!err) err = nfserrno(commit_metadata(fhp)); - fh_unlock(fhp); fh_drop_write(fhp); @@ -1680,6 +1680,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp, if (d_really_is_negative(dold)) goto out_dput; host_err = vfs_link(dold, &init_user_ns, dirp, dnew, NULL); + fh_unlock(ffhp); if (!host_err) { err = nfserrno(commit_metadata(ffhp)); if (!err) @@ -1902,10 +1903,10 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, host_err = vfs_rmdir(&init_user_ns, dirp, rdentry); } + fh_unlock(fhp); if (!host_err) host_err = commit_metadata(fhp); dput(rdentry); - fh_unlock(fhp); iput(rinode); /* truncate the inode here */ out_drop_write: