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NFS: Convert lookups of the open context to RCU

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Reduce contention on the inode->i_lock by ensuring that we use RCU
when looking up the NFS open context.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust
2018-09-02 15:57:01 -04:00
parent 6ba0c4e5bb
commit 0de43976fb
6 changed files with 57 additions and 39 deletions
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37
fs/nfs/inode.c
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@@ -977,9 +977,9 @@ EXPORT_SYMBOL_GPL(alloc_nfs_open_context);
struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx)
{
if (ctx != NULL)
refcount_inc(&ctx->lock_context.count);
return ctx;
if (ctx != NULL && refcount_inc_not_zero(&ctx->lock_context.count))
return ctx;
return NULL;
}
EXPORT_SYMBOL_GPL(get_nfs_open_context);
@@ -988,13 +988,13 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
struct inode *inode = d_inode(ctx->dentry);
struct super_block *sb = ctx->dentry->d_sb;
if (!list_empty(&ctx->list)) {
if (!refcount_dec_and_lock(&ctx->lock_context.count, &inode->i_lock))
return;
list_del(&ctx->list);
spin_unlock(&inode->i_lock);
} else if (!refcount_dec_and_test(&ctx->lock_context.count))
if (!refcount_dec_and_test(&ctx->lock_context.count))
return;
if (!list_empty(&ctx->list)) {
spin_lock(&inode->i_lock);
list_del_rcu(&ctx->list);
spin_unlock(&inode->i_lock);
}
if (inode != NULL)
NFS_PROTO(inode)->close_context(ctx, is_sync);
if (ctx->cred != NULL)
@@ -1002,7 +1002,7 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
dput(ctx->dentry);
nfs_sb_deactive(sb);
kfree(ctx->mdsthreshold);
kfree(ctx);
kfree_rcu(ctx, rcu_head);
}
void put_nfs_open_context(struct nfs_open_context *ctx)
@@ -1026,10 +1026,7 @@ void nfs_inode_attach_open_context(struct nfs_open_context *ctx)
struct nfs_inode *nfsi = NFS_I(inode);
spin_lock(&inode->i_lock);
if (ctx->mode & FMODE_WRITE)
list_add(&ctx->list, &nfsi->open_files);
else
list_add_tail(&ctx->list, &nfsi->open_files);
list_add_tail_rcu(&ctx->list, &nfsi->open_files);
spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL_GPL(nfs_inode_attach_open_context);
@@ -1050,16 +1047,17 @@ struct nfs_open_context *nfs_find_open_context(struct inode *inode, struct rpc_c
struct nfs_inode *nfsi = NFS_I(inode);
struct nfs_open_context *pos, *ctx = NULL;
spin_lock(&inode->i_lock);
list_for_each_entry(pos, &nfsi->open_files, list) {
rcu_read_lock();
list_for_each_entry_rcu(pos, &nfsi->open_files, list) {
if (cred != NULL && pos->cred != cred)
continue;
if ((pos->mode & (FMODE_READ|FMODE_WRITE)) != mode)
continue;
ctx = get_nfs_open_context(pos);
break;
if (ctx)
break;
}
spin_unlock(&inode->i_lock);
rcu_read_unlock();
return ctx;
}
@@ -1077,9 +1075,6 @@ void nfs_file_clear_open_context(struct file *filp)
if (ctx->error < 0)
invalidate_inode_pages2(inode->i_mapping);
filp->private_data = NULL;
spin_lock(&inode->i_lock);
list_move_tail(&ctx->list, &NFS_I(inode)->open_files);
spin_unlock(&inode->i_lock);
put_nfs_open_context_sync(ctx);
}
}