From: Jeff Layton <jlayton@redhat.com>
To: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, tj@kernel.org
Subject: [PATCH v2 1/6] idr: introduce idr_alloc_cyclic
Date: Wed, 27 Mar 2013 15:29:33 -0400 [thread overview]
Message-ID: <1364412578-7462-2-git-send-email-jlayton@redhat.com> (raw)
In-Reply-To: <1364412578-7462-1-git-send-email-jlayton@redhat.com>
Thus spake Tejun Heo:
Ooh, BTW, the cyclic allocation is broken. It's prone to -ENOSPC
after the first wraparound. There are several cyclic users in the
kernel and I think it probably would be best to implement cyclic
support in idr.
This patch does that by adding new idr_alloc_cyclic function that such
users in the kernel can use. With this, there's no need for a caller to
keep track of the last value used as that's now tracked internally.
This should prevent the ENOSPC problems that can hit when the "last
allocated" counter exceeds INT_MAX.
Later patches will convert existing cyclic users to the new interface.
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
include/linux/idr.h | 2 ++
lib/idr.c | 27 +++++++++++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/include/linux/idr.h b/include/linux/idr.h
index 2640c7e..a470ac3 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -42,6 +42,7 @@ struct idr {
struct idr_layer *id_free;
int layers; /* only valid w/o concurrent changes */
int id_free_cnt;
+ int cur; /* current pos for cyclic allocation */
spinlock_t lock;
};
@@ -75,6 +76,7 @@ struct idr {
void *idr_find_slowpath(struct idr *idp, int id);
void idr_preload(gfp_t gfp_mask);
int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
+int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
int idr_for_each(struct idr *idp,
int (*fn)(int id, void *p, void *data), void *data);
void *idr_get_next(struct idr *idp, int *nextid);
diff --git a/lib/idr.c b/lib/idr.c
index 322e281..cca4b93 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -495,6 +495,33 @@ int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
}
EXPORT_SYMBOL_GPL(idr_alloc);
+/**
+ * idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
+ * @idr: the (initialized) idr
+ * @ptr: pointer to be associated with the new id
+ * @start: the minimum id (inclusive)
+ * @end: the maximum id (exclusive, <= 0 for max)
+ * @gfp_mask: memory allocation flags
+ *
+ * Essentially the same as idr_alloc, but prefers to allocate progressively
+ * higher ids if it can. If the "cur" counter wraps, then it will start again
+ * at the "start" end of the range and allocate one that has already been used.
+ */
+int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,
+ gfp_t gfp_mask)
+{
+ int id;
+
+ id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);
+ if (id == -ENOSPC)
+ id = idr_alloc(idr, ptr, start, end, gfp_mask);
+
+ if (likely(id >= 0))
+ idr->cur = id + 1;
+ return id;
+}
+EXPORT_SYMBOL(idr_alloc_cyclic);
+
static void idr_remove_warning(int id)
{
printk(KERN_WARNING
--
1.7.11.7
next prev parent reply other threads:[~2013-03-27 19:29 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-27 19:29 [PATCH v2 0/6] idr: add idr_alloc_cyclic and convert existing cyclic users Jeff Layton
2013-03-27 19:29 ` Jeff Layton [this message]
2013-03-27 19:29 ` [PATCH v2 2/6] amso1100: convert to using idr_alloc_cyclic Jeff Layton
2013-03-27 19:35 ` Tejun Heo
2013-03-27 19:29 ` [PATCH v2 3/6] mlx4: " Jeff Layton
2013-03-27 19:29 ` [PATCH v2 4/6] nfsd: convert nfs4_alloc_stid to use idr_alloc_cyclic Jeff Layton
2013-04-03 19:24 ` J. Bruce Fields
2013-03-27 19:29 ` [PATCH v2 5/6] inotify: convert inotify_add_to_idr " Jeff Layton
2013-03-27 19:29 ` [PATCH v2 6/6] sctp: convert sctp_assoc_set_id " Jeff Layton
2013-03-28 13:53 ` Neil Horman
2013-03-28 14:04 ` Neil Horman
2013-03-31 10:23 ` Jeff Layton
2013-03-27 19:38 ` [PATCH v2 0/6] idr: add idr_alloc_cyclic and convert existing cyclic users Tejun Heo
2013-03-27 19:50 ` Andrew Morton
2013-03-27 19:58 ` Jeff Layton
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