Doug / smarc-fsl-linux-kernel

Download as
Browse Code ยป

Commit f49f9baac8f63de9cbc17a0a84e04060496e8e76

Authored by Fred Isaman
Committed by Trond Myklebust
1 parent 9f52c2525e
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

pnfs: fix pnfs lock inversion of i_lock and cl_lock 

The pnfs code was using throughout the lock order i_lock, cl_lock.
This conflicts with the nfs delegation code.  Rework the pnfs code
to avoid taking both locks simultaneously.

Currently the code takes the double lock to add/remove the layout to a
nfs_client list, while atomically checking that the list of lsegs is
empty.  To avoid this, we rely on existing serializations.  When a
layout is initialized with lseg count equal zero, LAYOUTGET's
openstateid serialization is in effect, making it safe to assume it
stays zero unless we change it.  And once a layout's lseg count drops
to zero, it is set as DESTROYED and so will stay at zero.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

Showing 2 changed files with 26 additions and 18 deletions Side-by-side Diff

fs/nfs/callback_proc.c
Diff comments   View file @ f49f9ba
... ... @@ -188,10 +188,10 @@
188 188 rv = NFS4ERR_DELAY;
189 189 list_del_init(&lo->plh_bulk_recall);
190 190 spin_unlock(&ino->i_lock);
  191 + pnfs_free_lseg_list(&free_me_list);
191 192 put_layout_hdr(lo);
192 193 iput(ino);
193 194 }
194   - pnfs_free_lseg_list(&free_me_list);
195 195 return rv;
196 196 }
197 197  
... ... @@ -247,13 +247,6 @@
247 247 BUG_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
248 248 list_del(&lseg->pls_list);
249 249 if (list_empty(&lseg->pls_layout->plh_segs)) {
250   - struct nfs_client *clp;
251   -
252   - clp = NFS_SERVER(ino)->nfs_client;
253   - spin_lock(&clp->cl_lock);
254   - /* List does not take a reference, so no need for put here */
255   - list_del_init(&lseg->pls_layout->plh_layouts);
256   - spin_unlock(&clp->cl_lock);
257 250 set_bit(NFS_LAYOUT_DESTROYED, &lseg->pls_layout->plh_flags);
258 251 /* Matched by initial refcount set in alloc_init_layout_hdr */
259 252 put_layout_hdr_locked(lseg->pls_layout);
260 253  
261 254  
... ... @@ -319,11 +312,27 @@
319 312 return invalid - removed;
320 313 }
321 314  
  315 +/* note free_me must contain lsegs from a single layout_hdr */
322 316 void
323 317 pnfs_free_lseg_list(struct list_head *free_me)
324 318 {
325 319 struct pnfs_layout_segment *lseg, *tmp;
  320 + struct pnfs_layout_hdr *lo;
326 321  
  322 + if (list_empty(free_me))
  323 + return;
  324 +
  325 + lo = list_first_entry(free_me, struct pnfs_layout_segment,
  326 + pls_list)->pls_layout;
  327 +
  328 + if (test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags)) {
  329 + struct nfs_client *clp;
  330 +
  331 + clp = NFS_SERVER(lo->plh_inode)->nfs_client;
  332 + spin_lock(&clp->cl_lock);
  333 + list_del_init(&lo->plh_layouts);
  334 + spin_unlock(&clp->cl_lock);
  335 + }
327 336 list_for_each_entry_safe(lseg, tmp, free_me, pls_list) {
328 337 list_del(&lseg->pls_list);
329 338 free_lseg(lseg);
... ... @@ -705,6 +714,7 @@
705 714 struct nfs_client *clp = NFS_SERVER(ino)->nfs_client;
706 715 struct pnfs_layout_hdr *lo;
707 716 struct pnfs_layout_segment *lseg = NULL;
  717 + bool first = false;
708 718  
709 719 if (!pnfs_enabled_sb(NFS_SERVER(ino)))
710 720 return NULL;
... ... @@ -735,7 +745,10 @@
735 745 atomic_inc(&lo->plh_outstanding);
736 746  
737 747 get_layout_hdr(lo);
738   - if (list_empty(&lo->plh_segs)) {
  748 + if (list_empty(&lo->plh_segs))
  749 + first = true;
  750 + spin_unlock(&ino->i_lock);
  751 + if (first) {
739 752 /* The lo must be on the clp list if there is any
740 753 * chance of a CB_LAYOUTRECALL(FILE) coming in.
741 754 */
742 755  
... ... @@ -744,17 +757,12 @@
744 757 list_add_tail(&lo->plh_layouts, &clp->cl_layouts);
745 758 spin_unlock(&clp->cl_lock);
746 759 }
747   - spin_unlock(&ino->i_lock);
748 760  
749 761 lseg = send_layoutget(lo, ctx, iomode);
750   - if (!lseg) {
751   - spin_lock(&ino->i_lock);
752   - if (list_empty(&lo->plh_segs)) {
753   - spin_lock(&clp->cl_lock);
754   - list_del_init(&lo->plh_layouts);
755   - spin_unlock(&clp->cl_lock);
756   - }
757   - spin_unlock(&ino->i_lock);
  762 + if (!lseg && first) {
  763 + spin_lock(&clp->cl_lock);
  764 + list_del_init(&lo->plh_layouts);
  765 + spin_unlock(&clp->cl_lock);
758 766 }
759 767 atomic_dec(&lo->plh_outstanding);
760 768 put_layout_hdr(lo);