nfs4: resend LAYOUTGET when there is a race that changes the seqid

pnfs_layout_process will check the returned layout stateid against what
the kernel has in-core. If it turns out that the stateid we received is
older, then we should resend the LAYOUTGET instead of falling back to
MDS I/O.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Cc: stable@vger.kernel.org # 3.18+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 93496c0..5a8ae21 100644 (file)
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -872,33 +872,38 @@ send_layoutget(struct pnfs_layout_hdr *lo,
 
        dprintk("--> %s\n", __func__);
 
-       lgp = kzalloc(sizeof(*lgp), gfp_flags);
-       if (lgp == NULL)
-               return NULL;
+       /*
+        * Synchronously retrieve layout information from server and
+        * store in lseg. If we race with a concurrent seqid morphing
+        * op, then re-send the LAYOUTGET.
+        */
+       do {
+               lgp = kzalloc(sizeof(*lgp), gfp_flags);
+               if (lgp == NULL)
+                       return NULL;
+
+               i_size = i_size_read(ino);
+
+               lgp->args.minlength = PAGE_CACHE_SIZE;
+               if (lgp->args.minlength > range->length)
+                       lgp->args.minlength = range->length;
+               if (range->iomode == IOMODE_READ) {
+                       if (range->offset >= i_size)
+                               lgp->args.minlength = 0;
+                       else if (i_size - range->offset < lgp->args.minlength)
+                               lgp->args.minlength = i_size - range->offset;
+               }
+               lgp->args.maxcount = PNFS_LAYOUT_MAXSIZE;
+               lgp->args.range = *range;
+               lgp->args.type = server->pnfs_curr_ld->id;
+               lgp->args.inode = ino;
+               lgp->args.ctx = get_nfs_open_context(ctx);
+               lgp->gfp_flags = gfp_flags;
+               lgp->cred = lo->plh_lc_cred;
 
-       i_size = i_size_read(ino);
+               lseg = nfs4_proc_layoutget(lgp, gfp_flags);
+       } while (lseg == ERR_PTR(-EAGAIN));
 
-       lgp->args.minlength = PAGE_CACHE_SIZE;
-       if (lgp->args.minlength > range->length)
-               lgp->args.minlength = range->length;
-       if (range->iomode == IOMODE_READ) {
-               if (range->offset >= i_size)
-                       lgp->args.minlength = 0;
-               else if (i_size - range->offset < lgp->args.minlength)
-                       lgp->args.minlength = i_size - range->offset;
-       }
-       lgp->args.maxcount = PNFS_LAYOUT_MAXSIZE;
-       lgp->args.range = *range;
-       lgp->args.type = server->pnfs_curr_ld->id;
-       lgp->args.inode = ino;
-       lgp->args.ctx = get_nfs_open_context(ctx);
-       lgp->gfp_flags = gfp_flags;
-       lgp->cred = lo->plh_lc_cred;
-
-       /* Synchronously retrieve layout information from server and
-        * store in lseg.
-        */
-       lseg = nfs4_proc_layoutget(lgp, gfp_flags);
        if (IS_ERR(lseg)) {
                switch (PTR_ERR(lseg)) {
                case -ENOMEM:
@@ -1687,6 +1692,7 @@ pnfs_layout_process(struct nfs4_layoutget *lgp)
                /* existing state ID, make sure the sequence number matches. */
                if (pnfs_layout_stateid_blocked(lo, &res->stateid)) {
                        dprintk("%s forget reply due to sequence\n", __func__);
+                       status = -EAGAIN;
                        goto out_forget_reply;
                }
                pnfs_set_layout_stateid(lo, &res->stateid, false);