pNFS/flexfiles: Fix a deadlock on LAYOUTGET
We encountered a deadlock where the SEQUENCE that accompanied the
LAYOUTGET triggered a session drain, while ff_layout_alloc_lseg
triggered a GETDEVICEINFO. The GETDEVICEINFO hung waiting for the
session drain, while the LAYOUTGET held the slot waiting for
alloc_lseg to finish.
Avoid this by moving the call to nfs4_find_get_deviceid out of
ff_layout_alloc_lseg and into nfs4_ff_layout_prepare_ds.
Signed-off-by: Fred Isaman <fred.isaman@gmail.com>
[dros@primarydata.com: pNFS/flexfiles: fix races in ff_layout_mirror_valid]
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
index 142bfd0..3cc39d1 100644
--- a/fs/nfs/flexfilelayout/flexfilelayoutdev.c
+++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
@@ -20,9 +20,11 @@
static unsigned int dataserver_timeo = NFS_DEF_TCP_RETRANS;
static unsigned int dataserver_retrans;
+static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg);
+
void nfs4_ff_layout_put_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
{
- if (mirror_ds)
+ if (!IS_ERR_OR_NULL(mirror_ds))
nfs4_put_deviceid_node(&mirror_ds->id_node);
}
@@ -182,12 +184,29 @@ static void ff_layout_mark_devid_invalid(struct pnfs_layout_segment *lseg,
}
static bool ff_layout_mirror_valid(struct pnfs_layout_segment *lseg,
- struct nfs4_ff_layout_mirror *mirror)
+ struct nfs4_ff_layout_mirror *mirror,
+ bool create)
{
- if (mirror == NULL || mirror->mirror_ds == NULL) {
- pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode,
- lseg);
- return false;
+ if (mirror == NULL || IS_ERR(mirror->mirror_ds))
+ goto outerr;
+ if (mirror->mirror_ds == NULL) {
+ if (create) {
+ struct nfs4_deviceid_node *node;
+ struct pnfs_layout_hdr *lh = lseg->pls_layout;
+ struct nfs4_ff_layout_ds *mirror_ds = ERR_PTR(-ENODEV);
+
+ node = nfs4_find_get_deviceid(NFS_SERVER(lh->plh_inode),
+ &mirror->devid, lh->plh_lc_cred,
+ GFP_KERNEL);
+ if (node)
+ mirror_ds = FF_LAYOUT_MIRROR_DS(node);
+
+ /* check for race with another call to this function */
+ if (cmpxchg(&mirror->mirror_ds, NULL, mirror_ds) &&
+ mirror_ds != ERR_PTR(-ENODEV))
+ nfs4_put_deviceid_node(node);
+ } else
+ goto outerr;
}
if (mirror->mirror_ds->ds == NULL) {
struct nfs4_deviceid_node *devid;
@@ -196,6 +215,9 @@ static bool ff_layout_mirror_valid(struct pnfs_layout_segment *lseg,
return false;
}
return true;
+outerr:
+ pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode, lseg);
+ return false;
}
static void extend_ds_error(struct nfs4_ff_layout_ds_err *err,
@@ -323,7 +345,7 @@ nfs4_ff_layout_select_ds_fh(struct pnfs_layout_segment *lseg, u32 mirror_idx)
struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, mirror_idx);
struct nfs_fh *fh = NULL;
- if (!ff_layout_mirror_valid(lseg, mirror)) {
+ if (!ff_layout_mirror_valid(lseg, mirror, false)) {
pr_err_ratelimited("NFS: %s: No data server for mirror offset index %d\n",
__func__, mirror_idx);
goto out;
@@ -363,7 +385,7 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx,
struct nfs_server *s = NFS_SERVER(ino);
unsigned int max_payload;
- if (!ff_layout_mirror_valid(lseg, mirror)) {
+ if (!ff_layout_mirror_valid(lseg, mirror, true)) {
pr_err_ratelimited("NFS: %s: No data server for offset index %d\n",
__func__, ds_idx);
goto out;
@@ -547,7 +569,11 @@ static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg)
for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
mirror = FF_LAYOUT_COMP(lseg, idx);
- if (mirror && mirror->mirror_ds) {
+ if (mirror) {
+ if (!mirror->mirror_ds)
+ return true;
+ if (IS_ERR(mirror->mirror_ds))
+ continue;
devid = &mirror->mirror_ds->id_node;
if (!ff_layout_test_devid_unavailable(devid))
return true;
@@ -565,8 +591,10 @@ static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
mirror = FF_LAYOUT_COMP(lseg, idx);
- if (!mirror || !mirror->mirror_ds)
+ if (!mirror || IS_ERR(mirror->mirror_ds))
return false;
+ if (!mirror->mirror_ds)
+ continue;
devid = &mirror->mirror_ds->id_node;
if (ff_layout_test_devid_unavailable(devid))
return false;
@@ -575,7 +603,7 @@ static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
return FF_LAYOUT_MIRROR_COUNT(lseg) != 0;
}
-bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
+static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
{
if (lseg->pls_range.iomode == IOMODE_READ)
return ff_read_layout_has_available_ds(lseg);