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.
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?
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
>>
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