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xarray: make xa_alloc_cyclic() return 0 on all success cases

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Change xa_alloc_cyclic() to return 0 even on wrap-around.  Do the same for
xa_alloc_cyclic_irq() and xa_alloc_cyclic_bh().

This will prevent any future bug of treating return of 1 as an error:
	int ret = xa_alloc_cyclic(...)
	if (ret) // currently mishandles ret==1
		goto failure;

If there will be someone interested in when wrap-around occurs, there is
still __xa_alloc_cyclic() that behaves as before.  For now there is no
such user.

Link: https://lkml.kernel.org/r/20250320102219.8101-1-przemyslaw.kitszel@intel.com
Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Link: https://lore.kernel.org/netdev/Z9gUd-5t8b5NX2wE@casper.infradead.org
Cc: Andriy Shevchenko <andriy.shevchenko@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Cc: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Przemek Kitszel 2025-03-20 11:22:19 +01:00 • committed by Andrew Morton
parent dbb9c166a0
commit 4c97a17a25
2 changed files with 30 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

24
include/linux/xarray.h
View file

@ -965,10 +965,12 @@ static inline int __must_check xa_alloc_irq(struct xarray *xa, u32 *id,
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Note that callers interested in whether wrapping has occurred should
* use __xa_alloc_cyclic() instead.
*
* Context: Any context. Takes and releases the xa_lock. May sleep if
* the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
* allocation succeeded after wrapping, -ENOMEM if memory could not be
* Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
@ -981,7 +983,7 @@ static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
xa_unlock(xa);
return err;
return err < 0 ? err : 0;
}
/**
@ -1002,10 +1004,12 @@ static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Note that callers interested in whether wrapping has occurred should
* use __xa_alloc_cyclic() instead.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
* allocation succeeded after wrapping, -ENOMEM if memory could not be
* Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
@ -1018,7 +1022,7 @@ static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
xa_unlock_bh(xa);
return err;
return err < 0 ? err : 0;
}
/**
@ -1039,10 +1043,12 @@ static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
* Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
* in xa_init_flags().
*
* Note that callers interested in whether wrapping has occurred should
* use __xa_alloc_cyclic() instead.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
* allocation succeeded after wrapping, -ENOMEM if memory could not be
* Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
static inline int xa_alloc_cyclic_irq(struct xarray *xa, u32 *id, void *entry,
@ -1055,7 +1061,7 @@ static inline int xa_alloc_cyclic_irq(struct xarray *xa, u32 *id, void *entry,
err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
xa_unlock_irq(xa);
return err;
return err < 0 ? err : 0;
}
/**

17
lib/test_xarray.c
View file

@ -1040,6 +1040,7 @@ static noinline void check_xa_alloc_3(struct xarray *xa, unsigned int base)
unsigned int i, id;
unsigned long index;
void *entry;
int ret;
XA_BUG_ON(xa, xa_alloc_cyclic(xa, &id, xa_mk_index(1), limit,
&next, GFP_KERNEL) != 0);
@ -1059,7 +1060,7 @@ static noinline void check_xa_alloc_3(struct xarray *xa, unsigned int base)
else
entry = xa_mk_index(i - 0x3fff);
XA_BUG_ON(xa, xa_alloc_cyclic(xa, &id, entry, limit,
&next, GFP_KERNEL) != (id == 1));
&next, GFP_KERNEL) != 0);
XA_BUG_ON(xa, xa_mk_index(id) != entry);
}
@ -1072,7 +1073,7 @@ static noinline void check_xa_alloc_3(struct xarray *xa, unsigned int base)
xa_limit_32b, &next, GFP_KERNEL) != 0);
XA_BUG_ON(xa, id != UINT_MAX);
XA_BUG_ON(xa, xa_alloc_cyclic(xa, &id, xa_mk_index(base),
xa_limit_32b, &next, GFP_KERNEL) != 1);
xa_limit_32b, &next, GFP_KERNEL) != 0);
XA_BUG_ON(xa, id != base);
XA_BUG_ON(xa, xa_alloc_cyclic(xa, &id, xa_mk_index(base + 1),
xa_limit_32b, &next, GFP_KERNEL) != 0);
@ -1080,7 +1081,19 @@ static noinline void check_xa_alloc_3(struct xarray *xa, unsigned int base)
xa_for_each(xa, index, entry)
xa_erase_index(xa, index);
XA_BUG_ON(xa, !xa_empty(xa));
/* check wrap-around return of __xa_alloc_cyclic() */
next = UINT_MAX;
XA_BUG_ON(xa, xa_alloc_cyclic(xa, &id, xa_mk_index(UINT_MAX),
xa_limit_32b, &next, GFP_KERNEL) != 0);
xa_lock(xa);
ret = __xa_alloc_cyclic(xa, &id, xa_mk_index(base), xa_limit_32b,
&next, GFP_KERNEL);
xa_unlock(xa);
XA_BUG_ON(xa, ret != 1);
xa_for_each(xa, index, entry)
xa_erase_index(xa, index);
XA_BUG_ON(xa, !xa_empty(xa));
}