Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753415AbZLAEPv (ORCPT ); Mon, 30 Nov 2009 23:15:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753148AbZLAEPu (ORCPT ); Mon, 30 Nov 2009 23:15:50 -0500 Received: from filer.fsl.cs.sunysb.edu ([130.245.126.2]:51149 "EHLO filer.fsl.cs.sunysb.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752907AbZLAEPt (ORCPT ); Mon, 30 Nov 2009 23:15:49 -0500 Date: Mon, 30 Nov 2009 23:15:23 -0500 Message-Id: <200912010415.nB14FNBV030439@agora.fsl.cs.sunysb.edu> From: Erez Zadok To: Valerie Aurora Cc: Jan Blunck , Alexander Viro , Christoph Hellwig , Andy Whitcroft , Scott James Remnant , Sandu Popa Marius , Jan Rekorajski , "J. R. Okajima" , Arnd Bergmann , Vladimir Dronnikov , Felix Fietkau , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 31/41] fallthru: Support for fallthru entries in union mount lookup In-reply-to: Your message of "Wed, 21 Oct 2009 12:19:29 PDT." <1256152779-10054-32-git-send-email-vaurora@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7996 Lines: 221 In message <1256152779-10054-32-git-send-email-vaurora@redhat.com>, Valerie Aurora writes: > A fallthru directory entry overrides the opaque flag for its parent > directory (for this directory entry only). Before, we stopped > building the union stack when we encountered an opaque directory; now > we include directories below opaque directories in the union stack and > check for opacity during lookup. > > Signed-off-by: Jan Blunck > Signed-off-by: Valerie Aurora > --- > fs/dcache.c | 7 +++---- > fs/namei.c | 59 +++++++++++++++++++++++++++++++++++++++++++++-------------- > 2 files changed, 48 insertions(+), 18 deletions(-) > > diff --git a/fs/dcache.c b/fs/dcache.c > index d80a3bb..ca8a661 100644 > --- a/fs/dcache.c > +++ b/fs/dcache.c > @@ -1086,7 +1086,7 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name) > static void __d_instantiate(struct dentry *dentry, struct inode *inode) > { > if (inode) { > - dentry->d_flags &= ~DCACHE_WHITEOUT; > + dentry->d_flags &= ~(DCACHE_WHITEOUT|DCACHE_FALLTHRU); > list_add(&dentry->d_alias, &inode->i_dentry); > } > dentry->d_inode = inode; > @@ -1638,9 +1638,8 @@ void d_delete(struct dentry * dentry) > > static void __d_rehash(struct dentry * entry, struct hlist_head *list) > { > - > - entry->d_flags &= ~DCACHE_UNHASHED; > - hlist_add_head_rcu(&entry->d_hash, list); > + entry->d_flags &= ~DCACHE_UNHASHED; > + hlist_add_head_rcu(&entry->d_hash, list); > } > > static void _d_rehash(struct dentry * entry) > diff --git a/fs/namei.c b/fs/namei.c > index 8d95eb1..61e94aa 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -416,6 +416,28 @@ static struct dentry *cache_lookup(struct dentry *parent, struct qstr *name, > return dentry; > } > > +/* > + * Theory of operation for opaque, whiteout, and fallthru: > + * > + * whiteout: Unconditionally stop lookup here - ENOENT > + * > + * opaque: Don't lookup in directories lower in the union stack > + * > + * fallthru: While looking up an entry, ignore the opaque flag for the > + * current directory only. > + * > + * A union stack is a linked list of directory dentries which appear > + * in the same place in the namespace. When constructing the union > + * stack, we include directories below opaque directories so that we > + * can properly handle fallthrus. All non-fallthru lookups have to > + * check for the opaque flag on the parent directory and obey it. > + * > + * In general, the code pattern is to lookup the the topmost entry > + * first (either the first visible non-negative dentry or a negative > + * dentry in the topmost layer of the union), then build the union > + * stack for the newly looked-up entry (if it is a directory). > + */ Excellent comment; even better said and clearer that the UM design doc. It's almost a pity such excellent description is buried in the middle of namei.c. > + > /** > * __cache_lookup_topmost - lookup the topmost (non-)negative dentry > * > @@ -445,6 +467,10 @@ static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name, > if (!dentry || (dentry->d_inode || d_is_whiteout(dentry))) > return !dentry; > > + /* Keep going through opaque directories if we found a fallthru */ > + if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry)) > + return !dentry; > + > /* look for the first non-negative or whiteout dentry */ > > while (follow_union_down(&nd->path.mnt, &nd->path.dentry)) { > @@ -470,6 +496,10 @@ static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name, > if (dentry->d_inode || d_is_whiteout(dentry)) > goto out_dput; > > + /* Stop the lookup on opaque parent and non-fallthru child */ > + if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry)) There's a lot of repetition of this condition: IS_OPAQUE(dentry->d_inode) && !d_is_fallthru(dentry) in this patch. Perhaps this should be macro'ized? #define CANT_GO_ON(d) (IS_OPAQUE((d)->d_inode) && !d_is_fallthru((d))) // :-) > + goto out_dput; > + > dput(dentry); > } > > @@ -528,9 +558,6 @@ static int __cache_lookup_build_union(struct nameidata *nd, struct qstr *name, > path_put(&last); > last.dentry = dentry; > last.mnt = mntget(nd->path.mnt); > - > - if (IS_OPAQUE(last.dentry->d_inode)) > - break; > } > > if (last.dentry != path->dentry) > @@ -570,8 +597,7 @@ static int cache_lookup_union(struct nameidata *nd, struct qstr *name, > > /* only directories can be part of a union stack */ > if (!path->dentry->d_inode || > - !S_ISDIR(path->dentry->d_inode->i_mode) || > - IS_OPAQUE(path->dentry->d_inode)) > + !S_ISDIR(path->dentry->d_inode->i_mode)) > goto out; > > /* Build the union stack for this part */ > @@ -738,6 +764,9 @@ static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name, > if (path->dentry->d_inode || d_is_whiteout(path->dentry)) > return 0; > > + if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry)) > + return 0; > + > while (follow_union_down(&nd->path.mnt, &nd->path.dentry)) { > name->hash = full_name_hash(name->name, name->len); > if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) { > @@ -758,6 +787,9 @@ static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name, > goto out; > } > > + if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry)) > + goto out; > + > dput(next.dentry); > } > out: > @@ -817,9 +849,6 @@ static int __real_lookup_build_union(struct nameidata *nd, struct qstr *name, > path_put(&last); > last.dentry = next.dentry; > last.mnt = mntget(next.mnt); > - > - if (IS_OPAQUE(last.dentry->d_inode)) > - break; > } > > if (last.dentry != path->dentry) > @@ -841,8 +870,7 @@ static int real_lookup_union(struct nameidata *nd, struct qstr *name, > > /* only directories can be part of a union stack */ > if (!path->dentry->d_inode || > - !S_ISDIR(path->dentry->d_inode->i_mode) || > - IS_OPAQUE(path->dentry->d_inode)) > + !S_ISDIR(path->dentry->d_inode->i_mode)) > goto out; > > /* Build the union stack for this part */ > @@ -1128,7 +1156,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name, > { > int err; > > - if (IS_MNT_UNION(nd->path.mnt) && !IS_OPAQUE(nd->path.dentry->d_inode)) > + if (IS_MNT_UNION(nd->path.mnt)) > goto need_union_lookup; > > path->dentry = __d_lookup(nd->path.dentry, name); > @@ -1679,6 +1707,9 @@ static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name, > if (path->dentry->d_inode || d_is_whiteout(path->dentry)) > return 0; > > + if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry)) > + return 0; > + > while (follow_union_down(&nd->path.mnt, &nd->path.dentry)) { > name->hash = full_name_hash(name->name, name->len); > if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) { > @@ -1701,6 +1732,9 @@ static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name, > goto out; > } > > + if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry)) > + goto out; > + > dput(next.dentry); > } > out: > @@ -1755,9 +1789,6 @@ static int __hash_lookup_build_union(struct nameidata *nd, struct qstr *name, > path_put(&last); > last.dentry = next.dentry; > last.mnt = mntget(next.mnt); > - > - if (IS_OPAQUE(last.dentry->d_inode)) > - break; > } > > if (last.dentry != path->dentry) > -- > 1.6.3.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Erez. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/