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/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index ca1012a..ef4c9d1 100644 (file)
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -183,7 +183,7 @@ ff_layout_add_mirror(struct pnfs_layout_hdr *lo,
 
        spin_lock(&inode->i_lock);
        list_for_each_entry(pos, &ff_layout->mirrors, mirrors) {
-               if (mirror->mirror_ds != pos->mirror_ds)
+               if (memcmp(&mirror->devid, &pos->devid, sizeof(pos->devid)) != 0)
                        continue;
                if (!ff_mirror_match_fh(mirror, pos))
                        continue;
@@ -360,19 +360,6 @@ static void ff_layout_sort_mirrors(struct nfs4_ff_layout_segment *fls)
        }
 }
 
-static void ff_layout_mark_devices_valid(struct nfs4_ff_layout_segment *fls)
-{
-       struct nfs4_deviceid_node *node;
-       int i;
-
-       if (!(fls->flags & FF_FLAGS_NO_IO_THRU_MDS))
-               return;
-       for (i = 0; i < fls->mirror_array_cnt; i++) {
-               node = &fls->mirror_array[i]->mirror_ds->id_node;
-               clear_bit(NFS_DEVICEID_UNAVAILABLE, &node->flags);
-       }
-}
-
 static struct pnfs_layout_segment *
 ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
                     struct nfs4_layoutget_res *lgr,
@@ -426,8 +413,6 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 
        for (i = 0; i < fls->mirror_array_cnt; i++) {
                struct nfs4_ff_layout_mirror *mirror;
-               struct nfs4_deviceid devid;
-               struct nfs4_deviceid_node *idnode;
                struct auth_cred acred = { .group_info = ff_zero_group };
                struct rpc_cred __rcu *cred;
                u32 ds_count, fh_count, id;
@@ -452,24 +437,10 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
                fls->mirror_array[i]->ds_count = ds_count;
 
                /* deviceid */
-               rc = decode_deviceid(&stream, &devid);
+               rc = decode_deviceid(&stream, &fls->mirror_array[i]->devid);
                if (rc)
                        goto out_err_free;
 
-               idnode = nfs4_find_get_deviceid(NFS_SERVER(lh->plh_inode),
-                                               &devid, lh->plh_lc_cred,
-                                               gfp_flags);
-               /*
-                * upon success, mirror_ds is allocated by previous
-                * getdeviceinfo, or newly by .alloc_deviceid_node
-                * nfs4_find_get_deviceid failure is indeed getdeviceinfo falure
-                */
-               if (idnode)
-                       fls->mirror_array[i]->mirror_ds =
-                               FF_LAYOUT_MIRROR_DS(idnode);
-               else
-                       goto out_err_free;
-
                /* efficiency */
                rc = -EIO;
                p = xdr_inline_decode(&stream, 4);
@@ -567,8 +538,6 @@ out_sort_mirrors:
        rc = ff_layout_check_layout(lgr);
        if (rc)
                goto out_err_free;
-       ff_layout_mark_devices_valid(fls);
-
        ret = &fls->generic_hdr;
        dprintk("<-- %s (success)\n", __func__);
 out_free_page:
@@ -2332,7 +2301,7 @@ ff_layout_mirror_prepare_stats(struct pnfs_layout_hdr *lo,
        list_for_each_entry(mirror, &ff_layout->mirrors, mirrors) {
                if (i >= dev_limit)
                        break;
-               if (!mirror->mirror_ds)
+               if (IS_ERR_OR_NULL(mirror->mirror_ds))
                        continue;
                if (!test_and_clear_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags))
                        continue;

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index 35221fe..7223c4e 100644 (file)
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -74,6 +74,7 @@ struct nfs4_ff_layout_mirror {
        struct list_head                mirrors;
        u32                             ds_count;
        u32                             efficiency;
+       struct nfs4_deviceid            devid;
        struct nfs4_ff_layout_ds        *mirror_ds;
        u32                             fh_versions_cnt;
        struct nfs_fh                   *fh_versions;
@@ -211,7 +212,6 @@ nfs4_ff_find_or_create_ds_client(struct pnfs_layout_segment *lseg,
                                 struct inode *inode);
 struct rpc_cred *ff_layout_get_ds_cred(struct pnfs_layout_segment *lseg,
                                       u32 ds_idx, struct rpc_cred *mdscred);
-bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg);
 bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg);
 bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg);
 

diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
index 142bfd0..3cc39d1 100644 (file)
--- 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);