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Date: Fri, 13 Jul 2018 10:05:50 +0800
From: jiangyiwen <jiangyiwen@...wei.com>
To: Matthew Wilcox <willy@...radead.org>,
Dominique Martinet <asmadeus@...ewreck.org>
CC: Latchesar Ionkov <lucho@...kov.net>,
Eric Van Hensbergen <ericvh@...il.com>,
<linux-kernel@...r.kernel.org>, Ron Minnich <rminnich@...dia.gov>,
<linux-fsdevel@...r.kernel.org>,
<v9fs-developer@...ts.sourceforge.net>
Subject: Re: [V9fs-developer] [PATCH v2 3/6] 9p: Replace the fidlist with an
IDR
On 2018/7/12 5:02, Matthew Wilcox wrote:
> The p9_idpool being used to allocate the IDs uses an IDR to allocate
> the IDs ... which we then keep in a doubly-linked list, rather than in
> the IDR which allocated them. We can use an IDR directly which saves
> two pointers per p9_fid, and a tiny memory allocation per p9_client.
>
> Signed-off-by: Matthew Wilcox <willy@...radead.org>
> ---
> include/net/9p/client.h | 9 +++------
> net/9p/client.c | 44 +++++++++++++++--------------------------
> 2 files changed, 19 insertions(+), 34 deletions(-)
>
> diff --git a/include/net/9p/client.h b/include/net/9p/client.h
> index 7af9d769b97d..e405729cd1c7 100644
> --- a/include/net/9p/client.h
> +++ b/include/net/9p/client.h
> @@ -27,6 +27,7 @@
> #define NET_9P_CLIENT_H
>
> #include <linux/utsname.h>
> +#include <linux/idr.h>
>
> /* Number of requests per row */
> #define P9_ROW_MAXTAG 255
> @@ -128,8 +129,7 @@ struct p9_req_t {
> * @proto_version: 9P protocol version to use
> * @trans_mod: module API instantiated with this client
> * @trans: tranport instance state and API
> - * @fidpool: fid handle accounting for session
> - * @fidlist: List of active fid handles
> + * @fids: All active FID handles
> * @tagpool - transaction id accounting for session
> * @reqs - 2D array of requests
> * @max_tag - current maximum tag id allocated
> @@ -169,8 +169,7 @@ struct p9_client {
> } tcp;
> } trans_opts;
>
> - struct p9_idpool *fidpool;
> - struct list_head fidlist;
> + struct idr fids;
>
> struct p9_idpool *tagpool;
> struct p9_req_t *reqs[P9_ROW_MAXTAG];
> @@ -188,7 +187,6 @@ struct p9_client {
> * @iounit: the server reported maximum transaction size for this file
> * @uid: the numeric uid of the local user who owns this handle
> * @rdir: readdir accounting structure (allocated on demand)
> - * @flist: per-client-instance fid tracking
> * @dlist: per-dentry fid tracking
> *
> * TODO: This needs lots of explanation.
> @@ -204,7 +202,6 @@ struct p9_fid {
>
> void *rdir;
>
> - struct list_head flist;
> struct hlist_node dlist; /* list of all fids attached to a dentry */
> };
>
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 389a2904b7b3..b89c7298267c 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -908,30 +908,29 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
> {
> int ret;
> struct p9_fid *fid;
> - unsigned long flags;
>
> p9_debug(P9_DEBUG_FID, "clnt %p\n", clnt);
> fid = kmalloc(sizeof(struct p9_fid), GFP_KERNEL);
> if (!fid)
> return NULL;
>
> - ret = p9_idpool_get(clnt->fidpool);
> - if (ret < 0)
> - goto error;
> - fid->fid = ret;
> -
> memset(&fid->qid, 0, sizeof(struct p9_qid));
> fid->mode = -1;
> fid->uid = current_fsuid();
> fid->clnt = clnt;
> fid->rdir = NULL;
> - spin_lock_irqsave(&clnt->lock, flags);
> - list_add(&fid->flist, &clnt->fidlist);
> - spin_unlock_irqrestore(&clnt->lock, flags);
> + fid->fid = 0;
>
> - return fid;
> + idr_preload(GFP_KERNEL);
It is best to use GFP_NOFS instead, or else it may cause some
unpredictable problem, because when out of memory it will
reclaim memory from v9fs.
> + spin_lock_irq(&clnt->lock);
> + ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
> + GFP_NOWAIT);
> + spin_unlock_irq(&clnt->lock);
use spin_lock instead, clnt->lock is not used in irq context.
> + idr_preload_end();
> +
> + if (!ret)
> + return fid;
>
> -error:
> kfree(fid);
> return NULL;
> }
> @@ -943,9 +942,8 @@ static void p9_fid_destroy(struct p9_fid *fid)
>
> p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
> clnt = fid->clnt;
> - p9_idpool_put(fid->fid, clnt->fidpool);
> spin_lock_irqsave(&clnt->lock, flags);
> - list_del(&fid->flist);
> + idr_remove(&clnt->fids, fid->fid);
> spin_unlock_irqrestore(&clnt->lock, flags);
> kfree(fid->rdir);
> kfree(fid);
> @@ -1028,7 +1026,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
> memcpy(clnt->name, client_id, strlen(client_id) + 1);
>
> spin_lock_init(&clnt->lock);
> - INIT_LIST_HEAD(&clnt->fidlist);
> + idr_init(&clnt->fids);
>
> err = p9_tag_init(clnt);
> if (err < 0)
> @@ -1048,18 +1046,12 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
> goto destroy_tagpool;
> }
>
> - clnt->fidpool = p9_idpool_create();
> - if (IS_ERR(clnt->fidpool)) {
> - err = PTR_ERR(clnt->fidpool);
> - goto put_trans;
> - }
> -
> p9_debug(P9_DEBUG_MUX, "clnt %p trans %p msize %d protocol %d\n",
> clnt, clnt->trans_mod, clnt->msize, clnt->proto_version);
>
> err = clnt->trans_mod->create(clnt, dev_name, options);
> if (err)
> - goto destroy_fidpool;
> + goto put_trans;
>
> if (clnt->msize > clnt->trans_mod->maxsize)
> clnt->msize = clnt->trans_mod->maxsize;
> @@ -1072,8 +1064,6 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
>
> close_trans:
> clnt->trans_mod->close(clnt);
> -destroy_fidpool:
> - p9_idpool_destroy(clnt->fidpool);
> put_trans:
> v9fs_put_trans(clnt->trans_mod);
> destroy_tagpool:
> @@ -1086,7 +1076,8 @@ EXPORT_SYMBOL(p9_client_create);
>
> void p9_client_destroy(struct p9_client *clnt)
> {
> - struct p9_fid *fid, *fidptr;
> + struct p9_fid *fid;
> + int id;
>
> p9_debug(P9_DEBUG_MUX, "clnt %p\n", clnt);
>
> @@ -1095,14 +1086,11 @@ void p9_client_destroy(struct p9_client *clnt)
>
> v9fs_put_trans(clnt->trans_mod);
>
> - list_for_each_entry_safe(fid, fidptr, &clnt->fidlist, flist) {
> + idr_for_each_entry(&clnt->fids, fid, id) {
> pr_info("Found fid %d not clunked\n", fid->fid);
> p9_fid_destroy(fid);
> }
>
> - if (clnt->fidpool)
> - p9_idpool_destroy(clnt->fidpool);
> -
I suggest add idr_destroy in the end.
> p9_tag_cleanup(clnt);
>
> kfree(clnt);
>
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