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pnfs: fix pnfs lock inversion of i_lock and cl_lock

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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>
This commit is contained in:
Fred Isaman 2011-02-03 18:28:52 +00:00 committed by Trond Myklebust
parent 9f52c2525e
commit f49f9baac8
2 changed files with 26 additions and 18 deletions
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2
fs/nfs/callback_proc.c
View File

@ -188,10 +188,10 @@ static u32 initiate_bulk_draining(struct nfs_client *clp,
rv = NFS4ERR_DELAY;
list_del_init(&lo->plh_bulk_recall);
spin_unlock(&ino->i_lock);
pnfs_free_lseg_list(&free_me_list);
put_layout_hdr(lo);
iput(ino);
}
pnfs_free_lseg_list(&free_me_list);
return rv;
}

42
fs/nfs/pnfs.c
View File

@ -247,13 +247,6 @@ put_lseg_locked(struct pnfs_layout_segment *lseg,
BUG_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
list_del(&lseg->pls_list);
if (list_empty(&lseg->pls_layout->plh_segs)) {
struct nfs_client *clp;
clp = NFS_SERVER(ino)->nfs_client;
spin_lock(&clp->cl_lock);
/* List does not take a reference, so no need for put here */
list_del_init(&lseg->pls_layout->plh_layouts);
spin_unlock(&clp->cl_lock);
set_bit(NFS_LAYOUT_DESTROYED, &lseg->pls_layout->plh_flags);
/* Matched by initial refcount set in alloc_init_layout_hdr */
put_layout_hdr_locked(lseg->pls_layout);
@ -319,11 +312,27 @@ mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo,
return invalid - removed;
}
/* note free_me must contain lsegs from a single layout_hdr */
void
pnfs_free_lseg_list(struct list_head *free_me)
{
struct pnfs_layout_segment *lseg, *tmp;
struct pnfs_layout_hdr *lo;
if (list_empty(free_me))
return;
lo = list_first_entry(free_me, struct pnfs_layout_segment,
pls_list)->pls_layout;
if (test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags)) {
struct nfs_client *clp;
clp = NFS_SERVER(lo->plh_inode)->nfs_client;
spin_lock(&clp->cl_lock);
list_del_init(&lo->plh_layouts);
spin_unlock(&clp->cl_lock);
}
list_for_each_entry_safe(lseg, tmp, free_me, pls_list) {
list_del(&lseg->pls_list);
free_lseg(lseg);
@ -705,6 +714,7 @@ pnfs_update_layout(struct inode *ino,
struct nfs_client *clp = NFS_SERVER(ino)->nfs_client;
struct pnfs_layout_hdr *lo;
struct pnfs_layout_segment *lseg = NULL;
bool first = false;
if (!pnfs_enabled_sb(NFS_SERVER(ino)))
return NULL;
@ -735,7 +745,10 @@ pnfs_update_layout(struct inode *ino,
atomic_inc(&lo->plh_outstanding);
get_layout_hdr(lo);
if (list_empty(&lo->plh_segs)) {
if (list_empty(&lo->plh_segs))
first = true;
spin_unlock(&ino->i_lock);
if (first) {
/* The lo must be on the clp list if there is any
* chance of a CB_LAYOUTRECALL(FILE) coming in.
*/
@ -744,17 +757,12 @@ pnfs_update_layout(struct inode *ino,
list_add_tail(&lo->plh_layouts, &clp->cl_layouts);
spin_unlock(&clp->cl_lock);
}
spin_unlock(&ino->i_lock);
lseg = send_layoutget(lo, ctx, iomode);
if (!lseg) {
spin_lock(&ino->i_lock);
if (list_empty(&lo->plh_segs)) {
spin_lock(&clp->cl_lock);
list_del_init(&lo->plh_layouts);
spin_unlock(&clp->cl_lock);
}
spin_unlock(&ino->i_lock);
if (!lseg && first) {
spin_lock(&clp->cl_lock);
list_del_init(&lo->plh_layouts);
spin_unlock(&clp->cl_lock);
}
atomic_dec(&lo->plh_outstanding);
put_layout_hdr(lo);