This patch introduces the Q_PATH flag to the quotactl cmd argument.
When given, the path given in the special argument to quotactl will
be the mount path where the filesystem is mounted, instead of a path
to the block device.
This is necessary for filesystems which do not have a block device as
backing store. Particularly this is done for upcoming UBIFS support.
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
fs/quota/quota.c | 66 ++++++++++++++++++++++++++++----------
include/uapi/linux/quota.h | 1 +
2 files changed, 50 insertions(+), 17 deletions(-)
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 6d16b2be5ac4..f653b27a9a4e 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -17,6 +17,7 @@
#include <linux/capability.h>
#include <linux/quotaops.h>
#include <linux/types.h>
+#include <linux/mount.h>
#include <linux/writeback.h>
#include <linux/nospec.h>
#include "compat.h"
@@ -859,25 +860,10 @@ static bool quotactl_cmd_onoff(int cmd)
(cmd == Q_XQUOTAON) || (cmd == Q_XQUOTAOFF);
}
-/*
- * look up a superblock on which quota ops will be performed
- * - use the name of a block device to find the superblock thereon
- */
-static struct super_block *quotactl_block(const char __user *special, int cmd)
+static struct super_block *quotactl_sb(dev_t dev, int cmd)
{
-#ifdef CONFIG_BLOCK
struct super_block *sb;
- struct filename *tmp = getname(special);
bool excl = false, thawed = false;
- int error;
- dev_t dev;
-
- if (IS_ERR(tmp))
- return ERR_CAST(tmp);
- error = lookup_bdev(tmp->name, &dev);
- putname(tmp);
- if (error)
- return ERR_PTR(error);
if (quotactl_cmd_onoff(cmd)) {
excl = true;
@@ -901,12 +887,50 @@ static struct super_block *quotactl_block(const char __user *special, int cmd)
goto retry;
}
return sb;
+}
+
+/*
+ * look up a superblock on which quota ops will be performed
+ * - use the name of a block device to find the superblock thereon
+ */
+static struct super_block *quotactl_block(const char __user *special, int cmd)
+{
+#ifdef CONFIG_BLOCK
+ struct filename *tmp = getname(special);
+ int error;
+ dev_t dev;
+ if (IS_ERR(tmp))
+ return ERR_CAST(tmp);
+ error = lookup_bdev(tmp->name, &dev);
+ putname(tmp);
+ if (error)
+ return ERR_PTR(error);
+
+ return quotactl_sb(dev, cmd);
#else
return ERR_PTR(-ENODEV);
#endif
}
+static struct super_block *quotactl_path(const char __user *special, int cmd)
+{
+ struct super_block *sb;
+ struct path path;
+ int error;
+
+ error = user_path_at(AT_FDCWD, special, LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT,
+ &path);
+ if (error)
+ return ERR_PTR(error);
+
+ sb = quotactl_sb(path.mnt->mnt_sb->s_dev, cmd);
+
+ path_put(&path);
+
+ return sb;
+}
+
/*
* This is the system call interface. This communicates with
* the user-level programs. Currently this only supports diskquota
@@ -920,6 +944,7 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
struct super_block *sb = NULL;
struct path path, *pathp = NULL;
int ret;
+ bool q_path;
cmds = cmd >> SUBCMDSHIFT;
type = cmd & SUBCMDMASK;
@@ -927,6 +952,9 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
if (type >= MAXQUOTAS)
return -EINVAL;
+ q_path = cmds & Q_PATH;
+ cmds &= ~Q_PATH;
+
/*
* As a special case Q_SYNC can be called without a specific device.
* It will iterate all superblocks that have quota enabled and call
@@ -951,7 +979,11 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
pathp = &path;
}
- sb = quotactl_block(special, cmds);
+ if (q_path)
+ sb = quotactl_path(special, cmds);
+ else
+ sb = quotactl_block(special, cmds);
+
if (IS_ERR(sb)) {
ret = PTR_ERR(sb);
goto out;
diff --git a/include/uapi/linux/quota.h b/include/uapi/linux/quota.h
index f17c9636a859..e1787c0df601 100644
--- a/include/uapi/linux/quota.h
+++ b/include/uapi/linux/quota.h
@@ -71,6 +71,7 @@
#define Q_GETQUOTA 0x800007 /* get user quota structure */
#define Q_SETQUOTA 0x800008 /* set user quota structure */
#define Q_GETNEXTQUOTA 0x800009 /* get disk limits and usage >= ID */
+#define Q_PATH 0x400000 /* quotactl special arg contains mount path */
/* Quota format type IDs */
#define QFMT_VFS_OLD 1
--
2.20.1
