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>
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@ -42,6 +42,7 @@ struct idr {
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struct idr_layer *id_free;
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struct idr_layer *id_free;
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int layers; /* only valid w/o concurrent changes */
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int layers; /* only valid w/o concurrent changes */
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int id_free_cnt;
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int id_free_cnt;
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int cur; /* current pos for cyclic allocation */
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spinlock_t lock;
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spinlock_t lock;
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};
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};
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@ -75,6 +76,7 @@ struct idr {
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void *idr_find_slowpath(struct idr *idp, int id);
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void *idr_find_slowpath(struct idr *idp, int id);
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void idr_preload(gfp_t gfp_mask);
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void idr_preload(gfp_t gfp_mask);
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int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
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int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
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int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
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int idr_for_each(struct idr *idp,
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int idr_for_each(struct idr *idp,
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int (*fn)(int id, void *p, void *data), void *data);
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int (*fn)(int id, void *p, void *data), void *data);
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void *idr_get_next(struct idr *idp, int *nextid);
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void *idr_get_next(struct idr *idp, int *nextid);
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27
lib/idr.c
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lib/idr.c
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@ -495,6 +495,33 @@ int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
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}
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}
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EXPORT_SYMBOL_GPL(idr_alloc);
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EXPORT_SYMBOL_GPL(idr_alloc);
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/**
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* idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
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* @idr: the (initialized) idr
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* @ptr: pointer to be associated with the new id
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* @start: the minimum id (inclusive)
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* @end: the maximum id (exclusive, <= 0 for max)
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* @gfp_mask: memory allocation flags
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*
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* Essentially the same as idr_alloc, but prefers to allocate progressively
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* higher ids if it can. If the "cur" counter wraps, then it will start again
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* at the "start" end of the range and allocate one that has already been used.
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*/
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int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,
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gfp_t gfp_mask)
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{
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int id;
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id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);
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if (id == -ENOSPC)
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id = idr_alloc(idr, ptr, start, end, gfp_mask);
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if (likely(id >= 0))
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idr->cur = id + 1;
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return id;
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}
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EXPORT_SYMBOL(idr_alloc_cyclic);
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static void idr_remove_warning(int id)
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static void idr_remove_warning(int id)
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{
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{
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printk(KERN_WARNING
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printk(KERN_WARNING
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