Commit c23266d5 authored by Andy Adamson's avatar Andy Adamson Committed by Trond Myklebust
Browse files

NFS4.1 Fix data server connection race 



Unlike meta data server mounts which support multiple mount points to
the same server via struct nfs_server, data servers support a single connection.

Concurrent calls to setup the data server connection can race where the first
call allocates the nfs_client struct, and before the cache struct nfs_client
pointer can be set, a second call also tries to setup the connection, finds the
already allocated nfs_client, bumps the reference count, re-initializes the
session,etc. This results in a hanging data server session after umount.

Signed-off-by: default avatarAndy Adamson <andros@netapp.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent d497ab97

fs/nfs/nfs4filelayout.h

+2 −0
Original line number Diff line number Diff line
@@ -70,6 +70,8 @@ struct nfs4_pnfs_ds { 
	struct list_head	ds_addrs;

	struct nfs_client	*ds_clp;

	atomic_t		ds_count;

	unsigned long		ds_state;

#define NFS4DS_CONNECTING	0	/* ds is establishing connection */

};



struct nfs4_file_layout_dsaddr {

fs/nfs/nfs4filelayoutdev.c

+24 −2
Original line number Diff line number Diff line
@@ -775,6 +775,22 @@ nfs4_fl_select_ds_fh(struct pnfs_layout_segment *lseg, u32 j) 
	return flseg->fh_array[i];

}



static void nfs4_wait_ds_connect(struct nfs4_pnfs_ds *ds)

{

	might_sleep();

	wait_on_bit(&ds->ds_state, NFS4DS_CONNECTING,

			nfs_wait_bit_killable, TASK_KILLABLE);

}



static void nfs4_clear_ds_conn_bit(struct nfs4_pnfs_ds *ds)

{

	smp_mb__before_clear_bit();

	clear_bit(NFS4DS_CONNECTING, &ds->ds_state);

	smp_mb__after_clear_bit();

	wake_up_bit(&ds->ds_state, NFS4DS_CONNECTING);

}





struct nfs4_pnfs_ds *

nfs4_fl_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx)

{
@@ -791,16 +807,22 @@ nfs4_fl_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx) 
		filelayout_mark_devid_invalid(devid);

		return NULL;

	}

	if (ds->ds_clp)

		return ds;



	if (!ds->ds_clp) {

	if (test_and_set_bit(NFS4DS_CONNECTING, &ds->ds_state) == 0) {

		struct nfs_server *s = NFS_SERVER(lseg->pls_layout->plh_inode);

		int err;



		err = nfs4_ds_connect(s, ds);

		if (err) {

			nfs4_mark_deviceid_unavailable(devid);

			return NULL;

			ds = NULL;

		}

		nfs4_clear_ds_conn_bit(ds);

	} else {

		/* Either ds is connected, or ds is NULL */

		nfs4_wait_ds_connect(ds);

	}

	return ds;

}

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