lkml.org 
[lkml]   [2015]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH 8/9] XFS: allow follow_link to often succeed in RCU-walk.
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 */



\
 
 \ /
  Last update: 2015-03-05 06:41    [W:1.244 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site