From: NeilBrown <neilb@suse.de>
To: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 8/9] XFS: allow follow_link to often succeed in RCU-walk.
Date: Thu, 05 Mar 2015 16:21:21 +1100 [thread overview]
Message-ID: <20150305052121.23906.99853.stgit@notabene.brown> (raw)
In-Reply-To: <20150305051530.23906.65097.stgit@notabene.brown>
If LOOKUP_RCU is set, use GFP_ATOMIC rather than GFP_KERNEL,
and try to get the ilock without blocking.
When these succeed, follow_link() can succeed without dropping
out of RCU-walk.
Signed-off-by: NeilBrown <neilb@suse.de>
---
fs/xfs/xfs_ioctl.c | 2 +-
fs/xfs/xfs_iops.c | 15 ++++++++++-----
fs/xfs/xfs_symlink.c | 11 +++++++++--
fs/xfs/xfs_symlink.h | 2 +-
4 files changed, 21 insertions(+), 9 deletions(-)
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index ac4feae45eb3..29d95a1b76c0 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -303,7 +303,7 @@ xfs_readlink_by_handle(
goto out_dput;
}
- error = xfs_readlink(XFS_I(dentry->d_inode), link);
+ error = xfs_readlink(XFS_I(dentry->d_inode), link, 0);
if (error)
goto out_kfree;
error = readlink_copy(hreq->ohandle, olen, link);
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 23cea798b777..2abab666df46 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -415,15 +415,20 @@ xfs_vn_follow_link(
struct nameidata *nd)
{
char *link;
- int error = -ENOMEM;
+ int error;
- if (nd_is_rcu(nd))
- return ERR_PTR(-ECHILD);
- link = kmalloc(MAXPATHLEN+1, GFP_KERNEL);
+ if (nd_is_rcu(nd)) {
+ error = -ECHILD;
+ link = kmalloc(MAXPATHLEN+1, GFP_ATOMIC);
+ } else {
+ error = -ENOMEM;
+ link = kmalloc(MAXPATHLEN+1, GFP_KERNEL);
+ }
if (!link)
goto out_err;
- error = xfs_readlink(XFS_I(dentry->d_inode), link);
+ error = xfs_readlink(XFS_I(dentry->d_inode), link,
+ nd_is_rcu(nd));
if (unlikely(error))
goto out_kfree;
diff --git a/fs/xfs/xfs_symlink.c b/fs/xfs/xfs_symlink.c
index 25791df6f638..87b5b2ba3d38 100644
--- a/fs/xfs/xfs_symlink.c
+++ b/fs/xfs/xfs_symlink.c
@@ -123,7 +123,8 @@ xfs_readlink_bmap(
int
xfs_readlink(
struct xfs_inode *ip,
- char *link)
+ char *link,
+ int rcu)
{
struct xfs_mount *mp = ip->i_mount;
xfs_fsize_t pathlen;
@@ -134,7 +135,11 @@ xfs_readlink(
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
- xfs_ilock(ip, XFS_ILOCK_SHARED);
+ if (rcu) {
+ if (xfs_ilock_nowait(ip, XFS_ILOCK_SHARED) == 0)
+ return -ECHILD;
+ } else
+ xfs_ilock(ip, XFS_ILOCK_SHARED);
pathlen = ip->i_d.di_size;
if (!pathlen)
@@ -153,6 +158,8 @@ xfs_readlink(
if (ip->i_df.if_flags & XFS_IFINLINE) {
memcpy(link, ip->i_df.if_u1.if_data, pathlen);
link[pathlen] = '\0';
+ } else if (rcu) {
+ error = -ECHILD;
} else {
error = xfs_readlink_bmap(ip, link);
}
diff --git a/fs/xfs/xfs_symlink.h b/fs/xfs/xfs_symlink.h
index e75245d09116..a71d26643e20 100644
--- a/fs/xfs/xfs_symlink.h
+++ b/fs/xfs/xfs_symlink.h
@@ -21,7 +21,7 @@
int xfs_symlink(struct xfs_inode *dp, struct xfs_name *link_name,
const char *target_path, umode_t mode, struct xfs_inode **ipp);
-int xfs_readlink(struct xfs_inode *ip, char *link);
+int xfs_readlink(struct xfs_inode *ip, char *link, int rcu);
int xfs_inactive_symlink(struct xfs_inode *ip);
#endif /* __XFS_SYMLINK_H */
next prev parent reply other threads:[~2015-03-05 5:21 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-05 5:21 [PATCH 0/9] Support follow_link in RCU-walk NeilBrown
2015-03-05 5:21 ` [PATCH 5/9] VFS/namei: enhance follow_link to support RCU-walk NeilBrown
2015-03-05 5:21 ` [PATCH 3/9] VFS/namei: new flag to support RCU symlinks: LOOKUP_LINK_RCU NeilBrown
2015-03-05 5:21 ` [PATCH 1/9] FS: make all ->follow_link handlers aware for LOOKUP_RCU NeilBrown
2015-03-05 5:21 ` [PATCH 9/9] NFS: support LOOKUP_RCU in nfs_follow_link NeilBrown
2015-03-05 5:21 ` [PATCH 6/9] VFS/namei: enable RCU-walk when following symlinks NeilBrown
2015-03-05 5:21 ` [PATCH 2/9] VFS/namei: use terminate_walk when symlink lookup fails NeilBrown
2015-03-05 5:21 ` [PATCH 7/9] VFS/namei: handle LOOKUP_RCU in page_follow_link_light NeilBrown
2015-03-05 5:21 ` NeilBrown [this message]
2015-03-05 5:21 ` [PATCH 4/9] VFS/namei: abort RCU-walk on symlink if atime needs updating NeilBrown
2015-03-05 6:05 ` [PATCH 0/9] Support follow_link in RCU-walk Al Viro
2015-03-05 13:52 ` John Stoffel
2015-03-05 16:00 ` Al Viro
2015-03-05 17:17 ` John Stoffel
2015-03-05 21:08 ` NeilBrown
2015-03-09 2:21 ` NeilBrown
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