linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: NeilBrown <neilb@suse.de>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 20/20] NFS: support LOOKUP_RCU in nfs_follow_link.
Date: Mon, 23 Mar 2015 13:37:40 +1100	[thread overview]
Message-ID: <20150323023740.8161.58517.stgit@notabene.brown> (raw)
In-Reply-To: <20150323023258.8161.32467.stgit@notabene.brown>

If the inode is valid and the page has been read in,
then we can follow a link in RCU-walk.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/nfs/inode.c         |   21 +++++++++++++++++++++
 fs/nfs/symlink.c       |   20 ++++++++++++++++++--
 include/linux/nfs_fs.h |    1 +
 3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index d42dff6d5e98..430899a789c6 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1162,6 +1162,27 @@ int nfs_revalidate_mapping_protected(struct inode *inode, struct address_space *
 	return __nfs_revalidate_mapping(inode, mapping, true);
 }
 
+int nfs_revalidate_mapping_rcu(struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	unsigned long *bitlock = &nfsi->flags;
+	int ret = 0;
+
+	if (IS_SWAPFILE(inode))
+		goto out;
+	if (nfs_mapping_need_revalidate_inode(inode)) {
+		ret = -ECHILD;
+		goto out;
+	}
+	spin_lock(&inode->i_lock);
+	if (test_bit(NFS_INO_INVALIDATING, bitlock) ||
+	    (nfsi->cache_validity & NFS_INO_INVALID_DATA))
+		ret = -ECHILD;
+	spin_unlock(&inode->i_lock);
+out:
+	return ret;
+}
+
 static unsigned long nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c
index 32bbac1bb4bc..1c0a94b3d12e 100644
--- a/fs/nfs/symlink.c
+++ b/fs/nfs/symlink.c
@@ -49,8 +49,24 @@ static void *nfs_follow_link(struct dentry *dentry, struct inode *inode,
 	struct page *page;
 	void *err;
 
-	if (flags & LOOKUP_RCU)
-		return ERR_PTR(-ECHILD);
+	if (flags & LOOKUP_RCU) {
+		err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
+		if (err)
+			goto read_failed;
+		page = find_get_page(inode->i_mapping, 0);
+		if (page &&
+		    (!PageUptodate(page) || PageHighMem(page))) {
+			put_page(page);
+			page = NULL;
+		}
+		if (!page) {
+			err = ERR_PTR(-ECHILD);
+			goto read_failed;
+		}
+		nd_set_link(page_address(page));
+		page = (void *)((unsigned long)page | 1);
+		return page;
+	}
 	err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
 	if (err)
 		goto read_failed;
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index b01ccf371fdc..2eea59456ebb 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -357,6 +357,7 @@ extern int nfs_revalidate_inode_rcu(struct nfs_server *server, struct inode *ino
 extern int __nfs_revalidate_inode(struct nfs_server *, struct inode *);
 extern int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping);
 extern int nfs_revalidate_mapping_protected(struct inode *inode, struct address_space *mapping);
+extern int nfs_revalidate_mapping_rcu(struct inode *inode);
 extern int nfs_setattr(struct dentry *, struct iattr *);
 extern void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr, struct nfs_fattr *);
 extern void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr,

  parent reply	other threads:[~2015-03-23  2:37 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-23  2:37 [PATCH 00/20] Support follow_link in RCU-walk - V3 NeilBrown
2015-03-23  2:37 ` [PATCH 02/20] STAGING/lustre: limit follow_link recursion using stack space NeilBrown
2015-04-18  3:01   ` Al Viro
2015-04-19 20:57     ` Andreas Dilger
2015-04-19 21:33       ` Al Viro
2015-04-20  2:29         ` Al Viro
2015-03-23  2:37 ` [PATCH 03/20] VFS: replace {, total_}link_count in task_struct with pointer to nameidata NeilBrown
2015-03-23  2:37 ` [PATCH 01/20] Documentation: remove outdated information from automount-support.txt NeilBrown
2015-03-23  2:37 ` [PATCH 10/20] security: make inode_follow_link RCU-walk aware NeilBrown
2015-03-23  2:37 ` [PATCH 04/20] ovl: rearrange ovl_follow_link to it doesn't need to call ->put_link NeilBrown
2015-03-23  2:37 ` [PATCH 07/20] VFS: remove nameidata args from ->follow_link NeilBrown
2015-03-23  2:37 ` [PATCH 06/20] SECURITY: remove nameidata arg from inode_follow_link NeilBrown
2015-03-23  2:37 ` [PATCH 05/20] VFS: replace nameidata arg to ->put_link with a char* NeilBrown
2015-03-23  2:37 ` [PATCH 09/20] security/selinux: pass 'flags' arg to avc_audit() and avc_has_perm_flags() NeilBrown
2015-03-23  2:37 ` [PATCH 11/20] VFS/namei: use terminate_walk when symlink lookup fails NeilBrown
2015-03-23  2:37 ` [PATCH 08/20] VFS: make all ->follow_link handlers aware for LOOKUP_RCU NeilBrown
2015-03-23  2:37 ` [PATCH 13/20] VFS/namei: abort RCU-walk on symlink if atime needs updating NeilBrown
2015-03-23  2:37 ` [PATCH 14/20] VFS/namei: add 'inode' arg to put_link() NeilBrown
2015-04-17 16:25   ` Al Viro
2015-04-17 19:09     ` Al Viro
2015-04-18  8:09       ` Al Viro
2015-03-23  2:37 ` [PATCH 16/20] VFS/namei: enable RCU-walk when following symlinks NeilBrown
2015-03-23  2:37 ` [PATCH 19/20] XFS: allow follow_link to often succeed in RCU-walk NeilBrown
2015-03-23  2:37 ` NeilBrown [this message]
2015-03-23  2:37 ` [PATCH 18/20] xfs: use RCU to free 'struct xfs_mount' NeilBrown
2015-03-23  2:37 ` [PATCH 17/20] VFS/namei: handle LOOKUP_RCU in page_follow_link_light NeilBrown
2015-03-23  2:37 ` [PATCH 12/20] VFS/namei: new flag to support RCU symlinks: LOOKUP_LINK_RCU NeilBrown
2015-03-23  2:37 ` [PATCH 15/20] VFS/namei: enhance follow_link to support RCU-walk NeilBrown
2015-03-25 23:23 ` [PATCH 00/20] Support follow_link in RCU-walk - V3 NeilBrown

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20150323023740.8161.58517.stgit@notabene.brown \
    --to=neilb@suse.de \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=viro@ZenIV.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).