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NFS4.1 Fix data server connection race

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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 <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Andy Adamson 2013-05-08 16:21:18 -04:00 committed by Trond Myklebust
parent d497ab9751
commit c23266d532
2 changed files with 26 additions and 2 deletions
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2
fs/nfs/nfs4filelayout.h
View file

@ -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 {

26
fs/nfs/nfs4filelayoutdev.c
View file

@ -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;
}