Messages in this thread | | | Date | Thu, 25 Apr 2013 11:17:48 +0400 | From | Stanislav Kinsbursky <> | Subject | Re: [PATCH] nfsd: enable UMH client tracker in container |
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24.04.2013 00:00, J. Bruce Fields пишет: > On Fri, Apr 19, 2013 at 07:01:50AM -0700, Jeff Layton wrote: >> On Tue, 16 Apr 2013 15:17:44 +0400 >> Stanislav Kinsbursky <skinsbursky@parallels.com> wrote: >> >>> This patch adds support for UserModeHelper tracker in a container. >>> The reason for this is that the only containerised tracker ("nfsdcld") is >>> going to be removed in 3.10 kernel, thus at least one more tracker have to be >>> containerised to replace the deprecated one. >>> UMH tracker looks more preferable comparing to legacy since it's the latest >>> one. >>> To make UMH tracker work in a container, we have to make sure, that it >>> executes right binary (i.e., this binary have to be taken from the container >>> environment). >>> But, UMH is a kernel thread, which works in global root environment by design >>> (kernel thread's root is inherited from kthreadd, which in turn inherited it's >>> root from global init). So, the root have to be swapped to the container's >>> one before binary execution. >>> >>> This patch passes "init" callback and private "data" to UMH interface, which >>> are used to swap root for spawned kernel thread. >>> >>> Note: container's root can be stored on stack, because UMH calls are >>> synchronous. >>> >>> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com> >>> --- >>> fs/nfsd/nfs4recover.c | 29 ++++++++++++++++++++++------- >>> 1 files changed, 22 insertions(+), 7 deletions(-) >>> >>> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c >>> index 899ca26..15f8de6 100644 >>> --- a/fs/nfsd/nfs4recover.c >>> +++ b/fs/nfsd/nfs4recover.c >>> @@ -38,6 +38,7 @@ >>> #include <linux/crypto.h> >>> #include <linux/sched.h> >>> #include <linux/fs.h> >>> +#include <linux/fs_struct.h> >>> #include <linux/module.h> >>> #include <net/net_namespace.h> >>> #include <linux/sunrpc/rpc_pipe_fs.h> >>> @@ -1122,12 +1123,28 @@ nfsd4_cltrack_legacy_recdir(const struct xdr_netobj *name) >>> return result; >>> } >>> >>> +static int nfsd_swap_root(struct subprocess_info *info, struct cred *new) >>> +{ >>> + struct path *root = info->data; >>> + struct fs_struct *fs = current->fs; >>> + struct path current_root; >>> + >>> + spin_lock(&fs->lock); >>> + current_root = fs->root; >>> + fs->root = *root; >>> + spin_unlock(&fs->lock); >>> + if (current_root.dentry) >>> + path_put(¤t_root); >>> + return 0; >>> +} >>> + >>> static int >>> nfsd4_umh_cltrack_upcall(char *cmd, char *arg, char *legacy) >>> { >>> char *envp[2]; >>> char *argv[4]; >>> int ret; >>> + struct path root; >>> >>> if (unlikely(!cltrack_prog[0])) { >>> dprintk("%s: cltrack_prog is disabled\n", __func__); >>> @@ -1146,7 +1163,11 @@ nfsd4_umh_cltrack_upcall(char *cmd, char *arg, char *legacy) >>> argv[2] = arg; >>> argv[3] = NULL; >>> >>> - ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC); >>> + get_fs_root(current->fs, &root); >>> + >>> + ret = call_usermodehelper_fns(argv[0], argv, envp, UMH_WAIT_PROC, >>> + nfsd_swap_root, NULL, &root); >>> + >>> /* >>> * Disable the upcall mechanism if we're getting an ENOENT or EACCES >>> * error. The admin can re-enable it on the fly by using sysfs >>> @@ -1185,12 +1206,6 @@ bin_to_hex_dup(const unsigned char *src, int srclen) >>> static int >>> nfsd4_umh_cltrack_init(struct net __attribute__((unused)) *net) >>> { >>> - /* XXX: The usermode helper s not working in container yet. */ >>> - if (net != &init_net) { >>> - WARN(1, KERN_ERR "NFSD: attempt to initialize umh client " >>> - "tracking in a container!\n"); >>> - return -EINVAL; >>> - } >>> return nfsd4_umh_cltrack_upcall("init", NULL, NULL); >>> } >>> >>> >> >> I think this looks correct and like it'll work, but I wonder whether >> we'd be best served by making this part of the UMH code itself? >> >> IOW, add some fields to the struct subprocess_info to hold the new >> root, and then do what you're doing in nfsd_swap_root before calling >> the "init" function? >> >> I imagine we'll eventually need do something similar for at least some >> of the callers of call_usermodehelper so it would make sense to me to >> not replicate copies of nfsd_swap_root all over the place. > > Agreed. >
Hmm. Yes, me too. Ok, I'll prepare patch for the UMH itself. And resend. Thanks, guys.
> --b. >
-- Best regards, Stanislav Kinsbursky -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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