From c23266d532b4de796a346f57a66587c5db17d27e Mon Sep 17 00:00:00 2001 From: Andy Adamson Date: Wed, 8 May 2013 16:21:18 -0400 Subject: 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: Andy Adamson Signed-off-by: Trond Myklebust --- fs/nfs/nfs4filelayout.h | 2 ++ fs/nfs/nfs4filelayoutdev.c | 26 ++++++++++++++++++++++++-- 2 files changed, 26 insertions(+), 2 deletions(-) (limited to 'fs/nfs') diff --git a/fs/nfs/nfs4filelayout.h b/fs/nfs/nfs4filelayout.h index b8da95548d3d..235ff952d3c8 100644 --- a/fs/nfs/nfs4filelayout.h +++ b/fs/nfs/nfs4filelayout.h @@ -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 { diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c index 1fe284f01f8b..661a0f611215 100644 --- a/fs/nfs/nfs4filelayoutdev.c +++ b/fs/nfs/nfs4filelayoutdev.c @@ -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; } -- cgit v1.2.3-59-g8ed1b