path: root/lib
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authorJeff Layton <jlayton@redhat.com>2013-04-29 16:21:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-29 18:28:41 -0700
commit3e6628c4b347a558965041290c5a92791dd4c741 (patch)
tree7f437ed24761f467b61c0a401fc8d6a6ca7fee3a /lib
parent27cf10e133c393f39399137b028c7b24d64ca06e (diff)
idr: introduce idr_alloc_cyclic()
As Tejun points out, there are several users of the IDR facility that attempt to use it in a cyclic fashion. These users are likely to see -ENOSPC errors after the counter wraps one or more times however. This patchset adds a new idr_alloc_cyclic routine and converts several of these users to it. Many of these users are in obscure parts of the kernel, and I don't have a good way to test some of them. The change is pretty straightforward though, so hopefully it won't be an issue. There is one other cyclic user of idr_alloc that I didn't touch in ipc/util.c. That one is doing some strange stuff that I didn't quite understand, but it looks like it should probably be converted later somehow. This patch: 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. Signed-off-by: Jeff Layton <jlayton@redhat.com> Reviewed-by: Tejun Heo <tj@kernel.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Eric Paris <eparis@parisplace.org> Cc: Jack Morgenstein <jackm@dev.mellanox.co.il> Cc: John McCutchan <john@johnmccutchan.com> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Or Gerlitz <ogerlitz@mellanox.com> Cc: Robert Love <rlove@rlove.org> Cc: Roland Dreier <roland@purestorage.com> Cc: Sridhar Samudrala <sri@us.ibm.com> Cc: Steve Wise <swise@opengridcomputing.com> Cc: Tom Tucker <tom@opengridcomputing.com> Cc: Vlad Yasevich <vyasevich@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
1 files changed, 27 insertions, 0 deletions
diff --git a/lib/idr.c b/lib/idr.c
index 322e2816f2fb..cca4b9302a71 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)
+ * 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;
static void idr_remove_warning(int id)

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