From: Jia He <justin.he@arm.com>
To: Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Jonathan Corbet <corbet@lwn.net>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@ftp.linux.org.uk>
Cc: Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ira Weiny <ira.weiny@intel.com>,
Eric Biggers <ebiggers@google.com>,
"Ahmed S. Darwish" <a.darwish@linutronix.de>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Jia He <justin.he@arm.com>
Subject: [PATCH RFC 1/3] fs: introduce helper d_path_fast()
Date: Sat, 8 May 2021 20:25:28 +0800 [thread overview]
Message-ID: <20210508122530.1971-2-justin.he@arm.com> (raw)
In-Reply-To: <20210508122530.1971-1-justin.he@arm.com>
This helper is similar to d_path except for not taking seqlock/spinlock.
Signed-off-by: Jia He <justin.he@arm.com>
---
fs/d_path.c | 50 ++++++++++++++++++++++++++++++++----------
include/linux/dcache.h | 1 +
2 files changed, 39 insertions(+), 12 deletions(-)
diff --git a/fs/d_path.c b/fs/d_path.c
index a69e2cd36e6e..985a5754a9f5 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -61,7 +61,7 @@ static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
* @root: root vfsmnt/dentry
* @buffer: pointer to the end of the buffer
* @buflen: pointer to buffer length
- *
+ * @need_lock: not ignoring renames and changes to the mount tree
* The function will first try to write out the pathname without taking any
* lock other than the RCU read lock to make sure that dentries won't go away.
* It only checks the sequence number of the global rename_lock as any change
@@ -74,7 +74,7 @@ static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
*/
static int prepend_path(const struct path *path,
const struct path *root,
- char **buffer, int *buflen)
+ char **buffer, int *buflen, bool need_lock)
{
struct dentry *dentry;
struct vfsmount *vfsmnt;
@@ -86,7 +86,8 @@ static int prepend_path(const struct path *path,
rcu_read_lock();
restart_mnt:
- read_seqbegin_or_lock(&mount_lock, &m_seq);
+ if (need_lock)
+ read_seqbegin_or_lock(&mount_lock, &m_seq);
seq = 0;
rcu_read_lock();
restart:
@@ -96,7 +97,8 @@ static int prepend_path(const struct path *path,
dentry = path->dentry;
vfsmnt = path->mnt;
mnt = real_mount(vfsmnt);
- read_seqbegin_or_lock(&rename_lock, &seq);
+ if (need_lock)
+ read_seqbegin_or_lock(&rename_lock, &seq);
while (dentry != root->dentry || vfsmnt != root->mnt) {
struct dentry * parent;
@@ -136,19 +138,21 @@ static int prepend_path(const struct path *path,
}
if (!(seq & 1))
rcu_read_unlock();
- if (need_seqretry(&rename_lock, seq)) {
+ if (need_lock && need_seqretry(&rename_lock, seq)) {
seq = 1;
goto restart;
}
- done_seqretry(&rename_lock, seq);
+ if (need_lock)
+ done_seqretry(&rename_lock, seq);
if (!(m_seq & 1))
rcu_read_unlock();
- if (need_seqretry(&mount_lock, m_seq)) {
+ if (need_lock && need_seqretry(&mount_lock, m_seq)) {
m_seq = 1;
goto restart_mnt;
}
- done_seqretry(&mount_lock, m_seq);
+ if (need_lock)
+ done_seqretry(&mount_lock, m_seq);
if (error >= 0 && bptr == *buffer) {
if (--blen < 0)
@@ -185,7 +189,7 @@ char *__d_path(const struct path *path,
int error;
prepend(&res, &buflen, "\0", 1);
- error = prepend_path(path, root, &res, &buflen);
+ error = prepend_path(path, root, &res, &buflen, true);
if (error < 0)
return ERR_PTR(error);
@@ -202,7 +206,7 @@ char *d_absolute_path(const struct path *path,
int error;
prepend(&res, &buflen, "\0", 1);
- error = prepend_path(path, &root, &res, &buflen);
+ error = prepend_path(path, &root, &res, &buflen, true);
if (error > 1)
error = -EINVAL;
@@ -225,7 +229,7 @@ static int path_with_deleted(const struct path *path,
return error;
}
- return prepend_path(path, root, buf, buflen);
+ return prepend_path(path, root, buf, buflen, true);
}
static int prepend_unreachable(char **buffer, int *buflen)
@@ -291,6 +295,28 @@ char *d_path(const struct path *path, char *buf, int buflen)
}
EXPORT_SYMBOL(d_path);
+/**
+ * d_path_fast - fast return the path of a dentry
+ * This helper is similar to d_path other than taking seqlock/spinlock.
+ */
+char *d_path_fast(const struct path *path, char *buf, int buflen)
+{
+ char *res = buf + buflen;
+ struct path root;
+ int error;
+
+ rcu_read_lock();
+ get_fs_root_rcu(current->fs, &root);
+ prepend(&res, &buflen, "\0", 1);
+ error = prepend_path(path, &root, &res, &buflen, false);
+ rcu_read_unlock();
+
+ if (error < 0)
+ res = ERR_PTR(error);
+ return res;
+}
+EXPORT_SYMBOL(d_path_fast);
+
/*
* Helper function for dentry_operations.d_dname() members
*/
@@ -445,7 +471,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
int buflen = PATH_MAX;
prepend(&cwd, &buflen, "\0", 1);
- error = prepend_path(&pwd, &root, &cwd, &buflen);
+ error = prepend_path(&pwd, &root, &cwd, &buflen, true);
rcu_read_unlock();
if (error < 0)
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c1e48014106f..9a00fb90824f 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -300,6 +300,7 @@ char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
extern char *__d_path(const struct path *, const struct path *, char *, int);
extern char *d_absolute_path(const struct path *, char *, int);
extern char *d_path(const struct path *, char *, int);
+extern char *d_path_fast(const struct path *, char *, int);
extern char *dentry_path_raw(struct dentry *, char *, int);
extern char *dentry_path(struct dentry *, char *, int);
--
2.17.1
next prev parent reply other threads:[~2021-05-08 12:29 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-08 12:25 [PATCH RFC 0/3] make '%pD' print full path for file Jia He
2021-05-08 12:25 ` Jia He [this message]
2021-05-08 15:30 ` [PATCH RFC 1/3] fs: introduce helper d_path_fast() Linus Torvalds
2021-05-08 19:13 ` Al Viro
2021-05-08 20:39 ` Linus Torvalds
2021-05-08 21:05 ` Al Viro
2021-05-08 22:17 ` Linus Torvalds
2021-05-08 22:46 ` Al Viro
2021-05-08 22:48 ` Linus Torvalds
2021-05-08 23:15 ` Al Viro
2021-05-08 23:18 ` Al Viro
2021-05-09 22:58 ` Eric W. Biederman
2021-05-10 12:51 ` Christian Brauner
2021-05-10 7:20 ` Christian Brauner
2021-05-08 22:42 ` Linus Torvalds
2021-05-08 22:47 ` Linus Torvalds
2021-05-09 2:28 ` Al Viro
2021-05-09 2:53 ` Linus Torvalds
2021-05-19 0:43 ` [PATCHSET] d_path cleanups Al Viro
2021-05-19 0:48 ` [PATCH 01/14] d_path: "\0" is {0,0}, not {0} Al Viro
2021-05-19 0:48 ` [PATCH 02/14] d_path: saner calling conventions for __dentry_path() Al Viro
2021-06-25 9:32 ` Justin He
2021-07-07 4:52 ` Justin He
2021-05-19 0:48 ` [PATCH 03/14] d_path: regularize handling of root dentry in __dentry_path() Al Viro
2021-07-07 4:50 ` Justin He
2021-05-19 0:48 ` [PATCH 04/14] d_path: get rid of path_with_deleted() Al Viro
2021-05-19 0:48 ` [PATCH 05/14] getcwd(2): saner logics around prepend_path() call Al Viro
2021-07-07 7:41 ` Justin He
2021-05-19 0:48 ` [PATCH 06/14] d_path: don't bother with return value of prepend() Al Viro
2021-06-24 6:13 ` Justin He
2021-05-19 0:48 ` [PATCH 07/14] d_path: lift -ENAMETOOLONG handling into callers of prepend_path() Al Viro
2021-06-25 9:18 ` Justin He
2021-06-28 5:20 ` Justin He
2021-05-19 0:48 ` [PATCH 08/14] d_path: make prepend_name() boolean Al Viro
2021-05-20 9:12 ` Justin He
2021-05-20 9:19 ` Andy Shevchenko
2021-05-20 14:53 ` Petr Mladek
2021-05-20 19:35 ` Al Viro
2021-07-07 7:43 ` Justin He
2021-05-19 0:48 ` [PATCH 09/14] d_path: introduce struct prepend_buffer Al Viro
2021-06-23 13:28 ` Justin He
2021-06-24 9:29 ` Enrico Weigelt, metux IT consult
2021-06-25 0:43 ` Justin He
2021-06-28 16:42 ` Enrico Weigelt, metux IT consult
2021-06-28 17:10 ` Andy Shevchenko
2021-05-19 0:48 ` [PATCH 10/14] d_path: prepend_path(): get rid of vfsmnt Al Viro
2021-05-19 0:48 ` [PATCH 11/14] d_path: prepend_path(): lift resetting b in case when we'd return 3 out of loop Al Viro
2021-05-19 0:48 ` [PATCH 12/14] d_path: prepend_path(): lift the inner loop into a new helper Al Viro
2021-05-19 8:07 ` Andy Shevchenko
2021-05-19 15:55 ` Al Viro
2021-07-07 7:52 ` Justin He
2021-05-19 0:49 ` [PATCH 13/14] d_path: prepend_path() is unlikely to return non-zero Al Viro
2021-06-25 8:00 ` Justin He
2021-06-25 17:58 ` Al Viro
2021-06-28 3:28 ` Justin He
2021-06-28 4:14 ` Al Viro
2021-06-28 4:36 ` Justin He
2021-06-28 4:37 ` Justin He
2021-05-19 0:49 ` [PATCH 14/14] getcwd(2): clean up error handling Al Viro
2021-07-07 8:03 ` Justin He
2021-06-24 6:05 ` [PATCH 01/14] d_path: "\0" is {0,0}, not {0} Justin He
2021-05-19 2:39 ` [PATCHSET] d_path cleanups Linus Torvalds
2021-06-22 14:00 ` Justin He
2021-05-09 2:20 ` [PATCH RFC 1/3] fs: introduce helper d_path_fast() Al Viro
2021-05-09 4:58 ` Al Viro
2021-05-10 16:16 ` Eric W. Biederman
2021-05-10 15:07 ` Justin He
2021-05-10 17:03 ` Linus Torvalds
2021-05-08 12:25 ` [PATCH RFC 2/3] lib/vsprintf.c: make %pD print full path for file Jia He
2021-05-10 3:46 ` Sergey Senozhatsky
2021-05-10 13:04 ` Petr Mladek
2021-05-10 14:25 ` Justin He
2021-05-27 7:20 ` Justin He
2021-05-27 9:14 ` Petr Mladek
2021-05-08 12:25 ` [PATCH RFC 3/3] s390/hmcdrv: remove the redundant directory path in debug message Jia He
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