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. Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Link: https://lore.kernel.org/netdev/Z9gUd-5t8b5NX2wE@xxxxxxxxxxxxxxxxxxxx Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx> --- CC: Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx> CC: Pierre Riteau <pierre@xxxxxxxxxxxx> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> CC: linux-fsdevel@xxxxxxxxxxxxxxx CC: linux-mm@xxxxxxxxx CC: linux-kernel@xxxxxxxxxxxxxxx Thanks to Andy and Dave for internal review feedback CC: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> CC: Dave Hansen <dave.hansen@xxxxxxxxx> --- include/linux/xarray.h | 24 +++++++++++++++--------- lib/test_xarray.c | 17 +++++++++++++++-- 2 files changed, 30 insertions(+), 11 deletions(-) diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 0b618ec04115..46eb751fd5df 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -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; } /** diff --git a/lib/test_xarray.c b/lib/test_xarray.c index 0e865bab4a10..393ffaaf090c 100644 --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -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); } @@ -1072,15 +1073,27 @@ 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); XA_BUG_ON(xa, id != base + 1); 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)); } -- 2.39.3
