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authorJan Kara <jack@suse.cz>2021-05-25 17:07:48 +0300
committerJan Kara <jack@suse.cz>2021-06-07 13:11:24 +0300
commit64c2c2c62f92339b176ea24403d8db16db36f9e6 (patch)
treedbe1ee81ca112e1b0f6e7c971fc29e6d0f217c0e /fs/quota
parent21e4e15a846f86643a43c291cbed5dca3639fc2b (diff)
downloadlinux-64c2c2c62f92339b176ea24403d8db16db36f9e6.tar.xz
quota: Change quotactl_path() systcall to an fd-based one
Some users have pointed out that path-based syscalls are problematic in some environments and at least directory fd argument and possibly also resolve flags are desirable for such syscalls. Rather than reimplementing all details of pathname lookup and following where it may eventually evolve, let's go for full file descriptor based syscall similar to how ioctl(2) works since the beginning. Managing of quotas isn't performance sensitive so the extra overhead of open does not matter and we are able to consume O_PATH descriptors as well which makes open cheap anyway. Also for frequent operations (such as retrieving usage information for all users) we can reuse single fd and in fact get even better performance as well as avoiding races with possible remounts etc. Tested-by: Sascha Hauer <s.hauer@pengutronix.de> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/quota')
-rw-r--r--fs/quota/quota.c28
1 files changed, 13 insertions, 15 deletions
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 05e4bd9ab6d6..2bcc9a6f1bfc 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -968,31 +968,30 @@ out:
return ret;
}
-SYSCALL_DEFINE4(quotactl_path, unsigned int, cmd, const char __user *,
- mountpoint, qid_t, id, void __user *, addr)
+SYSCALL_DEFINE4(quotactl_fd, unsigned int, fd, unsigned int, cmd,
+ qid_t, id, void __user *, addr)
{
struct super_block *sb;
- struct path mountpath;
unsigned int cmds = cmd >> SUBCMDSHIFT;
unsigned int type = cmd & SUBCMDMASK;
+ struct fd f;
int ret;
- if (type >= MAXQUOTAS)
- return -EINVAL;
+ f = fdget_raw(fd);
+ if (!f.file)
+ return -EBADF;
- ret = user_path_at(AT_FDCWD, mountpoint,
- LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT, &mountpath);
- if (ret)
- return ret;
-
- sb = mountpath.mnt->mnt_sb;
+ ret = -EINVAL;
+ if (type >= MAXQUOTAS)
+ goto out;
if (quotactl_cmd_write(cmds)) {
- ret = mnt_want_write(mountpath.mnt);
+ ret = mnt_want_write(f.file->f_path.mnt);
if (ret)
goto out;
}
+ sb = f.file->f_path.mnt->mnt_sb;
if (quotactl_cmd_onoff(cmds))
down_write(&sb->s_umount);
else
@@ -1006,9 +1005,8 @@ SYSCALL_DEFINE4(quotactl_path, unsigned int, cmd, const char __user *,
up_read(&sb->s_umount);
if (quotactl_cmd_write(cmds))
- mnt_drop_write(mountpath.mnt);
+ mnt_drop_write(f.file->f_path.mnt);
out:
- path_put(&mountpath);
-
+ fdput(f);
return ret;
}