On Wed, Oct 02, 2013 at 05:32:32PM +0300, Benny Halevy wrote:
> On 2013-10-02 01:14, J. Bruce Fields wrote:
> > See previous comments. What guarantees these superblock pointers stay
> > good as long as they're in the cache?
>
> Currently, the dependency on nfsd.ko should hold them but that should go away.
I don't see how that prevents anyone from unmounting a filesystem.
> Trying to think about referencing svc_export instead, we use find_sbid_id
> to get to the superblock in nfsd4_getdevinfo since we have no current fh.
> And we need the superblock to call into the fs sb->s_pnfs_op->get_device_info
> later in nfsd4_encode_getdevinfo.
>
> Just to make sure, we can safely get to the sb via exp->ex_path.dentry->d_inode->i_sb
> right?
Right.
--b.
>
> Benny
>
> >
> > --b.
> >
> > On Thu, Sep 26, 2013 at 02:40:31PM -0400, Benny Halevy wrote:
> >> From: Benny Halevy <bhalevy@xxxxxxxxxxx>
> >>
> >> Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
> >> [pnfsd: alloc_sid should kmalloc a object not a pointer]
> >> Signed-off-by: Bian Naimeng <biannm@xxxxxxxxxxxxxx>
> >> Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
> >> Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxxxxxx>
> >> ---
> >> fs/nfsd/nfs4pnfsd.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >> fs/nfsd/pnfsd.h | 2 +
> >> 2 files changed, 122 insertions(+)
> >>
> >> diff --git a/fs/nfsd/nfs4pnfsd.c b/fs/nfsd/nfs4pnfsd.c
> >> index cb28207..9a7cbc9 100644
> >> --- a/fs/nfsd/nfs4pnfsd.c
> >> +++ b/fs/nfsd/nfs4pnfsd.c
> >> @@ -25,3 +25,123 @@
> >>
> >> #define NFSDDBG_FACILITY NFSDDBG_PNFS
> >>
> >> +static DEFINE_SPINLOCK(layout_lock);
> >> +
> >> +/* hash table for nfsd4_pnfs_deviceid.sbid */
> >> +#define SBID_HASH_BITS 8
> >> +#define SBID_HASH_SIZE (1 << SBID_HASH_BITS)
> >> +#define SBID_HASH_MASK (SBID_HASH_SIZE - 1)
> >> +
> >> +struct sbid_tracker {
> >> + u64 id;
> >> + struct super_block *sb;
> >> + struct list_head hash;
> >> +};
> >> +
> >> +static u64 current_sbid;
> >> +static struct list_head sbid_hashtbl[SBID_HASH_SIZE];
> >> +
> >> +static unsigned long
> >> +sbid_hashval(struct super_block *sb)
> >> +{
> >> + return hash_ptr(sb, SBID_HASH_BITS);
> >> +}
> >> +
> >> +static struct sbid_tracker *
> >> +alloc_sbid(void)
> >> +{
> >> + return kmalloc(sizeof(struct sbid_tracker), GFP_KERNEL);
> >> +}
> >> +
> >> +static void
> >> +destroy_sbid(struct sbid_tracker *sbid)
> >> +{
> >> + spin_lock(&layout_lock);
> >> + list_del(&sbid->hash);
> >> + spin_unlock(&layout_lock);
> >> + kfree(sbid);
> >> +}
> >> +
> >> +void
> >> +nfsd4_free_pnfs_slabs(void)
> >> +{
> >> + int i;
> >> + struct sbid_tracker *sbid;
> >> +
> >> + for (i = 0; i < SBID_HASH_SIZE; i++) {
> >> + while (!list_empty(&sbid_hashtbl[i])) {
> >> + sbid = list_first_entry(&sbid_hashtbl[i],
> >> + struct sbid_tracker,
> >> + hash);
> >> + destroy_sbid(sbid);
> >> + }
> >> + }
> >> +}
> >> +
> >> +int
> >> +nfsd4_init_pnfs_slabs(void)
> >> +{
> >> + int i;
> >> +
> >> + for (i = 0; i < SBID_HASH_SIZE; i++)
> >> + INIT_LIST_HEAD(&sbid_hashtbl[i]);
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static u64
> >> +alloc_init_sbid(struct super_block *sb)
> >> +{
> >> + struct sbid_tracker *sbid;
> >> + struct sbid_tracker *new = alloc_sbid();
> >> + unsigned long hash_idx = sbid_hashval(sb);
> >> + u64 id = 0;
> >> +
> >> + if (likely(new)) {
> >> + spin_lock(&layout_lock);
> >> + id = ++current_sbid;
> >> + new->id = (id << SBID_HASH_BITS) | (hash_idx & SBID_HASH_MASK);
> >> + id = new->id;
> >> + BUG_ON(id == 0);
> >> + new->sb = sb;
> >> +
> >> + list_for_each_entry (sbid, &sbid_hashtbl[hash_idx], hash)
> >> + if (sbid->sb == sb) {
> >> + kfree(new);
> >> + id = sbid->id;
> >> + spin_unlock(&layout_lock);
> >> + return id;
> >> + }
> >> + list_add(&new->hash, &sbid_hashtbl[hash_idx]);
> >> + spin_unlock(&layout_lock);
> >> + }
> >> + return id;
> >> +}
> >> +
> >> +static u64
> >> +find_create_sbid(struct super_block *sb)
> >> +{
> >> + struct sbid_tracker *sbid;
> >> + unsigned long hash_idx = sbid_hashval(sb);
> >> + int pos = 0;
> >> + u64 id = 0;
> >> +
> >> + spin_lock(&layout_lock);
> >> + list_for_each_entry (sbid, &sbid_hashtbl[hash_idx], hash) {
> >> + pos++;
> >> + if (sbid->sb != sb)
> >> + continue;
> >> + if (pos > 1) {
> >> + list_del(&sbid->hash);
> >> + list_add(&sbid->hash, &sbid_hashtbl[hash_idx]);
> >> + }
> >> + id = sbid->id;
> >> + break;
> >> + }
> >> + spin_unlock(&layout_lock);
> >> +
> >> + if (!id)
> >> + id = alloc_init_sbid(sb);
> >> +
> >> + return id;
> >> +}
> >> diff --git a/fs/nfsd/pnfsd.h b/fs/nfsd/pnfsd.h
> >> index 7c46791..29ea2e7 100644
> >> --- a/fs/nfsd/pnfsd.h
> >> +++ b/fs/nfsd/pnfsd.h
> >> @@ -36,4 +36,6 @@
> >>
> >> #include <linux/nfsd/nfsd4_pnfs.h>
> >>
> >> +#include "xdr4.h"
> >> +
> >> #endif /* LINUX_NFSD_PNFSD_H */
> >> --
> >> 1.8.3.1
> >>
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
