Commit 3e6628c4 authored by Jeff Layton's avatar Jeff Layton Committed by Linus Torvalds

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: default avatarJeff Layton <jlayton@redhat.com>
Reviewed-by: default avatarTejun 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 27cf10e1
...@@ -42,6 +42,7 @@ struct idr { ...@@ -42,6 +42,7 @@ struct idr {
struct idr_layer *id_free; struct idr_layer *id_free;
int layers; /* only valid w/o concurrent changes */ int layers; /* only valid w/o concurrent changes */
int id_free_cnt; int id_free_cnt;
int cur; /* current pos for cyclic allocation */
spinlock_t lock; spinlock_t lock;
}; };
...@@ -75,6 +76,7 @@ struct idr { ...@@ -75,6 +76,7 @@ struct idr {
void *idr_find_slowpath(struct idr *idp, int id); void *idr_find_slowpath(struct idr *idp, int id);
void idr_preload(gfp_t gfp_mask); 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(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 idr_for_each(struct idr *idp,
int (*fn)(int id, void *p, void *data), void *data); int (*fn)(int id, void *p, void *data), void *data);
void *idr_get_next(struct idr *idp, int *nextid); void *idr_get_next(struct idr *idp, int *nextid);
......
...@@ -495,6 +495,33 @@ int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask) ...@@ -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); 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) static void idr_remove_warning(int id)
{ {
printk(KERN_WARNING printk(KERN_WARNING
......
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