From 8229706e03e4147f3e22d1de0d30630cde6d18a9 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Thu, 1 Nov 2018 16:55:19 -0400 Subject: [PATCH 01/19] XArray: Fix xa_for_each with a single element at 0 The following sequence of calls would result in an infinite loop in xa_find_after(): xa_store(xa, 0, x, GFP_KERNEL); index = 0; xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) { } xa_find_after() was confusing the situation where we found no entry in the tree with finding a multiorder entry, so it would look for the successor entry forever. Just check for this case explicitly. Includes a few new checks in the test suite to be sure this doesn't reappear. Signed-off-by: Matthew Wilcox --- lib/test_xarray.c | 30 +++++++++++++++++++++++++++++- lib/xarray.c | 2 ++ 2 files changed, 31 insertions(+), 1 deletion(-) diff --git a/lib/test_xarray.c b/lib/test_xarray.c index aa47754150ce..126127658b49 100644 --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -702,7 +702,7 @@ static noinline void check_multi_find_2(struct xarray *xa) } } -static noinline void check_find(struct xarray *xa) +static noinline void check_find_1(struct xarray *xa) { unsigned long i, j, k; @@ -748,6 +748,34 @@ static noinline void check_find(struct xarray *xa) XA_BUG_ON(xa, xa_get_mark(xa, i, XA_MARK_0)); } XA_BUG_ON(xa, !xa_empty(xa)); +} + +static noinline void check_find_2(struct xarray *xa) +{ + void *entry; + unsigned long i, j, index = 0; + + xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) { + XA_BUG_ON(xa, true); + } + + for (i = 0; i < 1024; i++) { + xa_store_index(xa, index, GFP_KERNEL); + j = 0; + index = 0; + xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) { + XA_BUG_ON(xa, xa_mk_value(index) != entry); + XA_BUG_ON(xa, index != j++); + } + } + + xa_destroy(xa); +} + +static noinline void check_find(struct xarray *xa) +{ + check_find_1(xa); + check_find_2(xa); check_multi_find(xa); check_multi_find_2(xa); } diff --git a/lib/xarray.c b/lib/xarray.c index 8b176f009c08..c991ff4523ef 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1829,6 +1829,8 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp, entry = xas_find_marked(&xas, max, filter); else entry = xas_find(&xas, max); + if (xas.xa_node == XAS_BOUNDS) + break; if (xas.xa_shift) { if (xas.xa_index & ((1UL << xas.xa_shift) - 1)) continue; From 9ee5a3b7eeb190eb413e0fac3246022bd1baa05d Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Thu, 1 Nov 2018 22:52:06 -0400 Subject: [PATCH 02/19] XArray: Export __xa_foo to non-GPL modules Without this, it's not possible to use static inlines like xa_store_bh() and xa_erase_irq(). Signed-off-by: Matthew Wilcox --- lib/xarray.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/lib/xarray.c b/lib/xarray.c index c991ff4523ef..e7be4e47c6a9 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1334,7 +1334,7 @@ void *__xa_erase(struct xarray *xa, unsigned long index) XA_STATE(xas, xa, index); return xas_result(&xas, xas_store(&xas, NULL)); } -EXPORT_SYMBOL_GPL(__xa_erase); +EXPORT_SYMBOL(__xa_erase); /** * xa_store() - Store this entry in the XArray. @@ -1674,7 +1674,7 @@ void __xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark) if (entry) xas_set_mark(&xas, mark); } -EXPORT_SYMBOL_GPL(__xa_set_mark); +EXPORT_SYMBOL(__xa_set_mark); /** * __xa_clear_mark() - Clear this mark on this entry while locked. @@ -1692,7 +1692,7 @@ void __xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark) if (entry) xas_clear_mark(&xas, mark); } -EXPORT_SYMBOL_GPL(__xa_clear_mark); +EXPORT_SYMBOL(__xa_clear_mark); /** * xa_get_mark() - Inquire whether this mark is set on this entry. From fe2b51145c9ffd5a49013fe180e42e92ef0e6df9 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 4 Dec 2017 19:33:30 -0500 Subject: [PATCH 03/19] nilfs2: Use xa_erase_irq This code simply opencoded xa_erase_irq(). Signed-off-by: Matthew Wilcox --- fs/nilfs2/btnode.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c index de99db518571..f2129a5d9f23 100644 --- a/fs/nilfs2/btnode.c +++ b/fs/nilfs2/btnode.c @@ -266,9 +266,7 @@ void nilfs_btnode_abort_change_key(struct address_space *btnc, return; if (nbh == NULL) { /* blocksize == pagesize */ - xa_lock_irq(&btnc->i_pages); - __xa_erase(&btnc->i_pages, newkey); - xa_unlock_irq(&btnc->i_pages); + xa_erase_irq(&btnc->i_pages, newkey); unlock_page(ctxt->bh->b_page); } else brelse(nbh); From 4c0608f4a0e76dfb82d3accd20081f4bf47ed143 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 30 Oct 2018 09:45:55 -0400 Subject: [PATCH 04/19] XArray: Regularise xa_reserve The xa_reserve() function was a little unusual in that it attempted to be callable for all kinds of locking scenarios. Make it look like the other APIs with __xa_reserve, xa_reserve_bh and xa_reserve_irq variants. Signed-off-by: Matthew Wilcox --- Documentation/core-api/xarray.rst | 13 +++++ include/linux/xarray.h | 80 ++++++++++++++++++++++++++++++- lib/test_xarray.c | 6 +++ lib/xarray.c | 18 +++---- 4 files changed, 105 insertions(+), 12 deletions(-) diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst index a4e705108f42..65c77a81b689 100644 --- a/Documentation/core-api/xarray.rst +++ b/Documentation/core-api/xarray.rst @@ -105,6 +105,15 @@ may result in the entry being marked at some, but not all of the other indices. Storing into one index may result in the entry retrieved by some, but not all of the other indices changing. +Sometimes you need to ensure that a subsequent call to :c:func:`xa_store` +will not need to allocate memory. The :c:func:`xa_reserve` function +will store a reserved entry at the indicated index. Users of the normal +API will see this entry as containing ``NULL``. If you do not need to +use the reserved entry, you can call :c:func:`xa_release` to remove the +unused entry. If another user has stored to the entry in the meantime, +:c:func:`xa_release` will do nothing; if instead you want the entry to +become ``NULL``, you should use :c:func:`xa_erase`. + Finally, you can remove all entries from an XArray by calling :c:func:`xa_destroy`. If the XArray entries are pointers, you may wish to free the entries first. You can do this by iterating over all present @@ -167,6 +176,9 @@ Takes xa_lock internally: * :c:func:`xa_alloc` * :c:func:`xa_alloc_bh` * :c:func:`xa_alloc_irq` + * :c:func:`xa_reserve` + * :c:func:`xa_reserve_bh` + * :c:func:`xa_reserve_irq` * :c:func:`xa_destroy` * :c:func:`xa_set_mark` * :c:func:`xa_clear_mark` @@ -177,6 +189,7 @@ Assumes xa_lock held on entry: * :c:func:`__xa_erase` * :c:func:`__xa_cmpxchg` * :c:func:`__xa_alloc` + * :c:func:`__xa_reserve` * :c:func:`__xa_set_mark` * :c:func:`__xa_clear_mark` diff --git a/include/linux/xarray.h b/include/linux/xarray.h index d9514928ddac..c2cb0426c60c 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -291,7 +291,6 @@ void *xa_load(struct xarray *, unsigned long index); void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t); void *xa_cmpxchg(struct xarray *, unsigned long index, void *old, void *entry, gfp_t); -int xa_reserve(struct xarray *, unsigned long index, gfp_t); void *xa_store_range(struct xarray *, unsigned long first, unsigned long last, void *entry, gfp_t); bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t); @@ -455,6 +454,7 @@ void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t); void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old, void *entry, gfp_t); int __xa_alloc(struct xarray *, u32 *id, u32 max, void *entry, gfp_t); +int __xa_reserve(struct xarray *, unsigned long index, gfp_t); void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t); void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t); @@ -621,6 +621,84 @@ static inline int xa_alloc_irq(struct xarray *xa, u32 *id, u32 max, void *entry, return err; } +/** + * xa_reserve() - Reserve this index in the XArray. + * @xa: XArray. + * @index: Index into array. + * @gfp: Memory allocation flags. + * + * Ensures there is somewhere to store an entry at @index in the array. + * If there is already something stored at @index, this function does + * nothing. If there was nothing there, the entry is marked as reserved. + * Loading from a reserved entry returns a %NULL pointer. + * + * If you do not use the entry that you have reserved, call xa_release() + * or xa_erase() to free any unnecessary memory. + * + * Context: Any context. Takes and releases the xa_lock. + * May sleep if the @gfp flags permit. + * Return: 0 if the reservation succeeded or -ENOMEM if it failed. + */ +static inline +int xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp) +{ + int ret; + + xa_lock(xa); + ret = __xa_reserve(xa, index, gfp); + xa_unlock(xa); + + return ret; +} + +/** + * xa_reserve_bh() - Reserve this index in the XArray. + * @xa: XArray. + * @index: Index into array. + * @gfp: Memory allocation flags. + * + * A softirq-disabling version of xa_reserve(). + * + * Context: Any context. Takes and releases the xa_lock while + * disabling softirqs. + * Return: 0 if the reservation succeeded or -ENOMEM if it failed. + */ +static inline +int xa_reserve_bh(struct xarray *xa, unsigned long index, gfp_t gfp) +{ + int ret; + + xa_lock_bh(xa); + ret = __xa_reserve(xa, index, gfp); + xa_unlock_bh(xa); + + return ret; +} + +/** + * xa_reserve_irq() - Reserve this index in the XArray. + * @xa: XArray. + * @index: Index into array. + * @gfp: Memory allocation flags. + * + * An interrupt-disabling version of xa_reserve(). + * + * Context: Process context. Takes and releases the xa_lock while + * disabling interrupts. + * Return: 0 if the reservation succeeded or -ENOMEM if it failed. + */ +static inline +int xa_reserve_irq(struct xarray *xa, unsigned long index, gfp_t gfp) +{ + int ret; + + xa_lock_irq(xa); + ret = __xa_reserve(xa, index, gfp); + xa_unlock_irq(xa); + + return ret; +} + /* Everything below here is the Advanced API. Proceed with caution. */ /* diff --git a/lib/test_xarray.c b/lib/test_xarray.c index 126127658b49..e5294b20b52f 100644 --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -373,6 +373,12 @@ static noinline void check_reserve(struct xarray *xa) xa_erase_index(xa, 12345678); XA_BUG_ON(xa, !xa_empty(xa)); + /* And so does xa_insert */ + xa_reserve(xa, 12345678, GFP_KERNEL); + XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) != 0); + xa_erase_index(xa, 12345678); + XA_BUG_ON(xa, !xa_empty(xa)); + /* Can iterate through a reserved entry */ xa_store_index(xa, 5, GFP_KERNEL); xa_reserve(xa, 6, GFP_KERNEL); diff --git a/lib/xarray.c b/lib/xarray.c index e7be4e47c6a9..9cab8cfef8a8 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1488,7 +1488,7 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index, EXPORT_SYMBOL(__xa_cmpxchg); /** - * xa_reserve() - Reserve this index in the XArray. + * __xa_reserve() - Reserve this index in the XArray. * @xa: XArray. * @index: Index into array. * @gfp: Memory allocation flags. @@ -1496,33 +1496,29 @@ EXPORT_SYMBOL(__xa_cmpxchg); * Ensures there is somewhere to store an entry at @index in the array. * If there is already something stored at @index, this function does * nothing. If there was nothing there, the entry is marked as reserved. - * Loads from @index will continue to see a %NULL pointer until a - * subsequent store to @index. + * Loading from a reserved entry returns a %NULL pointer. * * If you do not use the entry that you have reserved, call xa_release() * or xa_erase() to free any unnecessary memory. * - * Context: Process context. Takes and releases the xa_lock, IRQ or BH safe - * if specified in XArray flags. May sleep if the @gfp flags permit. + * Context: Any context. Expects the xa_lock to be held on entry. May + * release the lock, sleep and reacquire the lock if the @gfp flags permit. * Return: 0 if the reservation succeeded or -ENOMEM if it failed. */ -int xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp) +int __xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp) { XA_STATE(xas, xa, index); - unsigned int lock_type = xa_lock_type(xa); void *curr; do { - xas_lock_type(&xas, lock_type); curr = xas_load(&xas); if (!curr) xas_store(&xas, XA_ZERO_ENTRY); - xas_unlock_type(&xas, lock_type); - } while (xas_nomem(&xas, gfp)); + } while (__xas_nomem(&xas, gfp)); return xas_error(&xas); } -EXPORT_SYMBOL(xa_reserve); +EXPORT_SYMBOL(__xa_reserve); #ifdef CONFIG_XARRAY_MULTI static void xas_set_range(struct xa_state *xas, unsigned long first, From c5beb07e7a06b24f4f27304f6282b5dbd929543b Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Wed, 31 Oct 2018 14:39:28 -0400 Subject: [PATCH 05/19] XArray: Unify xa_cmpxchg and __xa_cmpxchg xa_cmpxchg() was one of the largest functions in the xarray implementation. By turning it into a wrapper and having the callers take the lock (like several other functions), we save 160 bytes on a tinyconfig build and reduce the duplication in xarray.c. Signed-off-by: Matthew Wilcox --- include/linux/xarray.h | 113 +++++++++++++++++++++++++---------------- lib/xarray.c | 41 --------------- 2 files changed, 69 insertions(+), 85 deletions(-) diff --git a/include/linux/xarray.h b/include/linux/xarray.h index c2cb0426c60c..8e59d4fbd55e 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -289,8 +289,6 @@ struct xarray { void xa_init_flags(struct xarray *, gfp_t flags); void *xa_load(struct xarray *, unsigned long index); void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t); -void *xa_cmpxchg(struct xarray *, unsigned long index, - void *old, void *entry, gfp_t); void *xa_store_range(struct xarray *, unsigned long first, unsigned long last, void *entry, gfp_t); bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t); @@ -359,48 +357,6 @@ static inline void *xa_erase(struct xarray *xa, unsigned long index) return xa_store(xa, index, NULL, 0); } -/** - * xa_insert() - Store this entry in the XArray unless another entry is - * already present. - * @xa: XArray. - * @index: Index into array. - * @entry: New entry. - * @gfp: Memory allocation flags. - * - * If you would rather see the existing entry in the array, use xa_cmpxchg(). - * This function is for users who don't care what the entry is, only that - * one is present. - * - * Context: Process context. Takes and releases the xa_lock. - * May sleep if the @gfp flags permit. - * Return: 0 if the store succeeded. -EEXIST if another entry was present. - * -ENOMEM if memory could not be allocated. - */ -static inline int xa_insert(struct xarray *xa, unsigned long index, - void *entry, gfp_t gfp) -{ - void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp); - if (!curr) - return 0; - if (xa_is_err(curr)) - return xa_err(curr); - return -EEXIST; -} - -/** - * xa_release() - Release a reserved entry. - * @xa: XArray. - * @index: Index of entry. - * - * After calling xa_reserve(), you can call this function to release the - * reservation. If the entry at @index has been stored to, this function - * will do nothing. - */ -static inline void xa_release(struct xarray *xa, unsigned long index) -{ - xa_cmpxchg(xa, index, NULL, NULL, 0); -} - /** * xa_for_each() - Iterate over a portion of an XArray. * @xa: XArray. @@ -534,6 +490,61 @@ static inline void *xa_erase_irq(struct xarray *xa, unsigned long index) return entry; } +/** + * xa_cmpxchg() - Conditionally replace an entry in the XArray. + * @xa: XArray. + * @index: Index into array. + * @old: Old value to test against. + * @entry: New value to place in array. + * @gfp: Memory allocation flags. + * + * If the entry at @index is the same as @old, replace it with @entry. + * If the return value is equal to @old, then the exchange was successful. + * + * Context: Any context. Takes and releases the xa_lock. May sleep + * if the @gfp flags permit. + * Return: The old value at this index or xa_err() if an error happened. + */ +static inline void *xa_cmpxchg(struct xarray *xa, unsigned long index, + void *old, void *entry, gfp_t gfp) +{ + void *curr; + + xa_lock(xa); + curr = __xa_cmpxchg(xa, index, old, entry, gfp); + xa_unlock(xa); + + return curr; +} + +/** + * xa_insert() - Store this entry in the XArray unless another entry is + * already present. + * @xa: XArray. + * @index: Index into array. + * @entry: New entry. + * @gfp: Memory allocation flags. + * + * If you would rather see the existing entry in the array, use xa_cmpxchg(). + * This function is for users who don't care what the entry is, only that + * one is present. + * + * Context: Process context. Takes and releases the xa_lock. + * May sleep if the @gfp flags permit. + * Return: 0 if the store succeeded. -EEXIST if another entry was present. + * -ENOMEM if memory could not be allocated. + */ +static inline int xa_insert(struct xarray *xa, unsigned long index, + void *entry, gfp_t gfp) +{ + void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp); + if (!curr) + return 0; + if (xa_is_err(curr)) + return xa_err(curr); + return -EEXIST; +} + /** * xa_alloc() - Find somewhere to store this entry in the XArray. * @xa: XArray. @@ -699,6 +710,20 @@ int xa_reserve_irq(struct xarray *xa, unsigned long index, gfp_t gfp) return ret; } +/** + * xa_release() - Release a reserved entry. + * @xa: XArray. + * @index: Index of entry. + * + * After calling xa_reserve(), you can call this function to release the + * reservation. If the entry at @index has been stored to, this function + * will do nothing. + */ +static inline void xa_release(struct xarray *xa, unsigned long index) +{ + xa_cmpxchg(xa, index, NULL, NULL, 0); +} + /* Everything below here is the Advanced API. Proceed with caution. */ /* diff --git a/lib/xarray.c b/lib/xarray.c index 9cab8cfef8a8..77671d4a7910 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1406,47 +1406,6 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp) } EXPORT_SYMBOL(__xa_store); -/** - * xa_cmpxchg() - Conditionally replace an entry in the XArray. - * @xa: XArray. - * @index: Index into array. - * @old: Old value to test against. - * @entry: New value to place in array. - * @gfp: Memory allocation flags. - * - * If the entry at @index is the same as @old, replace it with @entry. - * If the return value is equal to @old, then the exchange was successful. - * - * Context: Process context. Takes and releases the xa_lock. May sleep - * if the @gfp flags permit. - * Return: The old value at this index or xa_err() if an error happened. - */ -void *xa_cmpxchg(struct xarray *xa, unsigned long index, - void *old, void *entry, gfp_t gfp) -{ - XA_STATE(xas, xa, index); - void *curr; - - if (WARN_ON_ONCE(xa_is_internal(entry))) - return XA_ERROR(-EINVAL); - - do { - xas_lock(&xas); - curr = xas_load(&xas); - if (curr == XA_ZERO_ENTRY) - curr = NULL; - if (curr == old) { - xas_store(&xas, entry); - if (xa_track_free(xa) && entry) - xas_clear_mark(&xas, XA_FREE_MARK); - } - xas_unlock(&xas); - } while (xas_nomem(&xas, gfp)); - - return xas_result(&xas, curr); -} -EXPORT_SYMBOL(xa_cmpxchg); - /** * __xa_cmpxchg() - Store this entry in the XArray. * @xa: XArray. From 9c16bb88905456a9b1299338041f05fa7699971b Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 5 Nov 2018 15:48:49 -0500 Subject: [PATCH 06/19] XArray: Turn xa_erase into an exported function Make xa_erase() take the spinlock and then call __xa_erase(), but make it out of line since it's such a common function. Signed-off-by: Matthew Wilcox --- include/linux/xarray.h | 18 +----------------- lib/xarray.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+), 17 deletions(-) diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 8e59d4fbd55e..4c839c17a99b 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -289,6 +289,7 @@ struct xarray { void xa_init_flags(struct xarray *, gfp_t flags); void *xa_load(struct xarray *, unsigned long index); void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t); +void *xa_erase(struct xarray *, unsigned long index); void *xa_store_range(struct xarray *, unsigned long first, unsigned long last, void *entry, gfp_t); bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t); @@ -340,23 +341,6 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark) return xa->xa_flags & XA_FLAGS_MARK(mark); } -/** - * xa_erase() - Erase this entry from the XArray. - * @xa: XArray. - * @index: Index of entry. - * - * This function is the equivalent of calling xa_store() with %NULL as - * the third argument. The XArray does not need to allocate memory, so - * the user does not need to provide GFP flags. - * - * Context: Process context. Takes and releases the xa_lock. - * Return: The entry which used to be at this index. - */ -static inline void *xa_erase(struct xarray *xa, unsigned long index) -{ - return xa_store(xa, index, NULL, 0); -} - /** * xa_for_each() - Iterate over a portion of an XArray. * @xa: XArray. diff --git a/lib/xarray.c b/lib/xarray.c index 77671d4a7910..b55aa8c1c20f 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1336,6 +1336,30 @@ void *__xa_erase(struct xarray *xa, unsigned long index) } EXPORT_SYMBOL(__xa_erase); +/** + * xa_erase() - Erase this entry from the XArray. + * @xa: XArray. + * @index: Index of entry. + * + * This function is the equivalent of calling xa_store() with %NULL as + * the third argument. The XArray does not need to allocate memory, so + * the user does not need to provide GFP flags. + * + * Context: Any context. Takes and releases the xa_lock. + * Return: The entry which used to be at this index. + */ +void *xa_erase(struct xarray *xa, unsigned long index) +{ + void *entry; + + xa_lock(xa); + entry = __xa_erase(xa, index); + xa_unlock(xa); + + return entry; +} +EXPORT_SYMBOL(xa_erase); + /** * xa_store() - Store this entry in the XArray. * @xa: XArray. From 84e5acb76dacb8ebd648a86a53907ce0dd616534 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 26 Oct 2018 14:41:29 -0400 Subject: [PATCH 07/19] XArray: Add xa_store_bh() and xa_store_irq() These convenience wrappers disable interrupts while taking the spinlock. A number of drivers would otherwise have to open-code these functions. Signed-off-by: Matthew Wilcox --- Documentation/core-api/xarray.rst | 5 ++- include/linux/xarray.h | 52 +++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+), 1 deletion(-) diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst index 65c77a81b689..8a6e2087de77 100644 --- a/Documentation/core-api/xarray.rst +++ b/Documentation/core-api/xarray.rst @@ -167,6 +167,8 @@ Takes RCU read lock: Takes xa_lock internally: * :c:func:`xa_store` + * :c:func:`xa_store_bh` + * :c:func:`xa_store_irq` * :c:func:`xa_insert` * :c:func:`xa_erase` * :c:func:`xa_erase_bh` @@ -247,7 +249,8 @@ Sharing the XArray with interrupt context is also possible, either using :c:func:`xa_lock_irqsave` in both the interrupt handler and process context, or :c:func:`xa_lock_irq` in process context and :c:func:`xa_lock` in the interrupt handler. Some of the more common patterns have helper -functions such as :c:func:`xa_erase_bh` and :c:func:`xa_erase_irq`. +functions such as :c:func:`xa_store_bh`, :c:func:`xa_store_irq`, +:c:func:`xa_erase_bh` and :c:func:`xa_erase_irq`. Sometimes you need to protect access to the XArray with a mutex because that lock sits above another mutex in the locking hierarchy. That does diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 4c839c17a99b..52d9732e4ec4 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -426,6 +426,58 @@ static inline int __xa_insert(struct xarray *xa, unsigned long index, return -EEXIST; } +/** + * xa_store_bh() - Store this entry in the XArray. + * @xa: XArray. + * @index: Index into array. + * @entry: New entry. + * @gfp: Memory allocation flags. + * + * This function is like calling xa_store() except it disables softirqs + * while holding the array lock. + * + * Context: Any context. Takes and releases the xa_lock while + * disabling softirqs. + * Return: The entry which used to be at this index. + */ +static inline void *xa_store_bh(struct xarray *xa, unsigned long index, + void *entry, gfp_t gfp) +{ + void *curr; + + xa_lock_bh(xa); + curr = __xa_store(xa, index, entry, gfp); + xa_unlock_bh(xa); + + return curr; +} + +/** + * xa_store_irq() - Erase this entry from the XArray. + * @xa: XArray. + * @index: Index into array. + * @entry: New entry. + * @gfp: Memory allocation flags. + * + * This function is like calling xa_store() except it disables interrupts + * while holding the array lock. + * + * Context: Process context. Takes and releases the xa_lock while + * disabling interrupts. + * Return: The entry which used to be at this index. + */ +static inline void *xa_store_irq(struct xarray *xa, unsigned long index, + void *entry, gfp_t gfp) +{ + void *curr; + + xa_lock_irq(xa); + curr = __xa_store(xa, index, entry, gfp); + xa_unlock_irq(xa); + + return curr; +} + /** * xa_erase_bh() - Erase this entry from the XArray. * @xa: XArray. From 611f318637daa5710a1d7a0e7dc6cda23914094a Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 5 Nov 2018 15:56:17 -0500 Subject: [PATCH 08/19] XArray: Unify xa_store and __xa_store Saves around 115 bytes on a tinyconfig build and reduces the amount of code duplication in the XArray implementation. Signed-off-by: Matthew Wilcox --- lib/xarray.c | 66 +++++++++++++++++++++++----------------------------- 1 file changed, 29 insertions(+), 37 deletions(-) diff --git a/lib/xarray.c b/lib/xarray.c index b55aa8c1c20f..a9d28013f9dc 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1360,43 +1360,6 @@ void *xa_erase(struct xarray *xa, unsigned long index) } EXPORT_SYMBOL(xa_erase); -/** - * xa_store() - Store this entry in the XArray. - * @xa: XArray. - * @index: Index into array. - * @entry: New entry. - * @gfp: Memory allocation flags. - * - * After this function returns, loads from this index will return @entry. - * Storing into an existing multislot entry updates the entry of every index. - * The marks associated with @index are unaffected unless @entry is %NULL. - * - * Context: Process context. Takes and releases the xa_lock. May sleep - * if the @gfp flags permit. - * Return: The old entry at this index on success, xa_err(-EINVAL) if @entry - * cannot be stored in an XArray, or xa_err(-ENOMEM) if memory allocation - * failed. - */ -void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp) -{ - XA_STATE(xas, xa, index); - void *curr; - - if (WARN_ON_ONCE(xa_is_internal(entry))) - return XA_ERROR(-EINVAL); - - do { - xas_lock(&xas); - curr = xas_store(&xas, entry); - if (xa_track_free(xa) && entry) - xas_clear_mark(&xas, XA_FREE_MARK); - xas_unlock(&xas); - } while (xas_nomem(&xas, gfp)); - - return xas_result(&xas, curr); -} -EXPORT_SYMBOL(xa_store); - /** * __xa_store() - Store this entry in the XArray. * @xa: XArray. @@ -1430,6 +1393,35 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp) } EXPORT_SYMBOL(__xa_store); +/** + * xa_store() - Store this entry in the XArray. + * @xa: XArray. + * @index: Index into array. + * @entry: New entry. + * @gfp: Memory allocation flags. + * + * After this function returns, loads from this index will return @entry. + * Storing into an existing multislot entry updates the entry of every index. + * The marks associated with @index are unaffected unless @entry is %NULL. + * + * Context: Any context. Takes and releases the xa_lock. + * May sleep if the @gfp flags permit. + * Return: The old entry at this index on success, xa_err(-EINVAL) if @entry + * cannot be stored in an XArray, or xa_err(-ENOMEM) if memory allocation + * failed. + */ +void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp) +{ + void *curr; + + xa_lock(xa); + curr = __xa_store(xa, index, entry, gfp); + xa_unlock(xa); + + return curr; +} +EXPORT_SYMBOL(xa_store); + /** * __xa_cmpxchg() - Store this entry in the XArray. * @xa: XArray. From d9c480435add8257f9069941f0e6196647f6d746 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 5 Nov 2018 16:15:56 -0500 Subject: [PATCH 09/19] XArray: Handle NULL pointers differently for allocation For allocating XArrays, it makes sense to distinguish beteen erasing an entry and storing NULL. Storing NULL keeps the index allocated with a NULL pointer associated with it while xa_erase() frees the index. Some existing IDR users rely on this ability. Signed-off-by: Matthew Wilcox --- Documentation/core-api/xarray.rst | 28 +++++++++++++++++++--------- lib/xarray.c | 13 ++++++++++--- 2 files changed, 29 insertions(+), 12 deletions(-) diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst index 8a6e2087de77..616ac406bf86 100644 --- a/Documentation/core-api/xarray.rst +++ b/Documentation/core-api/xarray.rst @@ -119,18 +119,27 @@ Finally, you can remove all entries from an XArray by calling to free the entries first. You can do this by iterating over all present entries in the XArray using the :c:func:`xa_for_each` iterator. -ID assignment -------------- +Allocating XArrays +------------------ + +If you use :c:func:`DEFINE_XARRAY_ALLOC` to define the XArray, or +initialise it by passing ``XA_FLAGS_ALLOC`` to :c:func:`xa_init_flags`, +the XArray changes to track whether entries are in use or not. You can call :c:func:`xa_alloc` to store the entry at any unused index in the XArray. If you need to modify the array from interrupt context, you can use :c:func:`xa_alloc_bh` or :c:func:`xa_alloc_irq` to disable -interrupts while allocating the ID. Unlike :c:func:`xa_store`, allocating -a ``NULL`` pointer does not delete an entry. Instead it reserves an -entry like :c:func:`xa_reserve` and you can release it using either -:c:func:`xa_erase` or :c:func:`xa_release`. To use ID assignment, the -XArray must be defined with :c:func:`DEFINE_XARRAY_ALLOC`, or initialised -by passing ``XA_FLAGS_ALLOC`` to :c:func:`xa_init_flags`, +interrupts while allocating the ID. + +Using :c:func:`xa_store`, :c:func:`xa_cmpxchg` or :c:func:`xa_insert` +will mark the entry as being allocated. Unlike a normal XArray, storing +``NULL`` will mark the entry as being in use, like :c:func:`xa_reserve`. +To free an entry, use :c:func:`xa_erase` (or :c:func:`xa_release` if +you only want to free the entry if it's ``NULL``). + +You cannot use ``XA_MARK_0`` with an allocating XArray as this mark +is used to track whether an entry is free or not. The other marks are +available for your use. Memory allocation ----------------- @@ -338,7 +347,8 @@ to :c:func:`xas_retry`, and retry the operation if it returns ``true``. - :c:func:`xa_is_zero` - Zero entries appear as ``NULL`` through the Normal API, but occupy an entry in the XArray which can be used to reserve the index for - future use. + future use. This is used by allocating XArrays for allocated entries + which are ``NULL``. Other internal entries may be added in the future. As far as possible, they will be handled by :c:func:`xas_retry`. diff --git a/lib/xarray.c b/lib/xarray.c index a9d28013f9dc..c3e2084aa313 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1382,10 +1382,12 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp) if (WARN_ON_ONCE(xa_is_internal(entry))) return XA_ERROR(-EINVAL); + if (xa_track_free(xa) && !entry) + entry = XA_ZERO_ENTRY; do { curr = xas_store(&xas, entry); - if (xa_track_free(xa) && entry) + if (xa_track_free(xa)) xas_clear_mark(&xas, XA_FREE_MARK); } while (__xas_nomem(&xas, gfp)); @@ -1446,6 +1448,8 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index, if (WARN_ON_ONCE(xa_is_internal(entry))) return XA_ERROR(-EINVAL); + if (xa_track_free(xa) && !entry) + entry = XA_ZERO_ENTRY; do { curr = xas_load(&xas); @@ -1453,7 +1457,7 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index, curr = NULL; if (curr == old) { xas_store(&xas, entry); - if (xa_track_free(xa) && entry) + if (xa_track_free(xa)) xas_clear_mark(&xas, XA_FREE_MARK); } } while (__xas_nomem(&xas, gfp)); @@ -1487,8 +1491,11 @@ int __xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp) do { curr = xas_load(&xas); - if (!curr) + if (!curr) { xas_store(&xas, XA_ZERO_ENTRY); + if (xa_track_free(xa)) + xas_clear_mark(&xas, XA_FREE_MARK); + } } while (__xas_nomem(&xas, gfp)); return xas_error(&xas); From 804dfaf01bcc9daa4298c608ba9018abf616ec48 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 5 Nov 2018 16:37:15 -0500 Subject: [PATCH 10/19] XArray: Fix Documentation Minor fixes. Signed-off-by: Matthew Wilcox --- Documentation/core-api/xarray.rst | 6 +++++- include/linux/xarray.h | 4 ++-- lib/xarray.c | 10 +++++----- 3 files changed, 12 insertions(+), 8 deletions(-) diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst index 616ac406bf86..dbe96cb5558e 100644 --- a/Documentation/core-api/xarray.rst +++ b/Documentation/core-api/xarray.rst @@ -74,7 +74,8 @@ using :c:func:`xa_load`. xa_store will overwrite any entry with the new entry and return the previous entry stored at that index. You can use :c:func:`xa_erase` instead of calling :c:func:`xa_store` with a ``NULL`` entry. There is no difference between an entry that has never -been stored to and one that has most recently had ``NULL`` stored to it. +been stored to, one that has been erased and one that has most recently +had ``NULL`` stored to it. You can conditionally replace an entry at an index by using :c:func:`xa_cmpxchg`. Like :c:func:`cmpxchg`, it will only succeed if @@ -114,6 +115,9 @@ unused entry. If another user has stored to the entry in the meantime, :c:func:`xa_release` will do nothing; if instead you want the entry to become ``NULL``, you should use :c:func:`xa_erase`. +If all entries in the array are ``NULL``, the :c:func:`xa_empty` function +will return ``true``. + Finally, you can remove all entries from an XArray by calling :c:func:`xa_destroy`. If the XArray entries are pointers, you may wish to free the entries first. You can do this by iterating over all present diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 52d9732e4ec4..564892e19f8c 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -487,7 +487,7 @@ static inline void *xa_store_irq(struct xarray *xa, unsigned long index, * the third argument. The XArray does not need to allocate memory, so * the user does not need to provide GFP flags. * - * Context: Process context. Takes and releases the xa_lock while + * Context: Any context. Takes and releases the xa_lock while * disabling softirqs. * Return: The entry which used to be at this index. */ @@ -622,7 +622,7 @@ static inline int xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, * Updates the @id pointer with the index, then stores the entry at that * index. A concurrent lookup will not see an uninitialised @id. * - * Context: Process context. Takes and releases the xa_lock while + * Context: Any context. Takes and releases the xa_lock while * disabling softirqs. May sleep if the @gfp flags permit. * Return: 0 on success, -ENOMEM if memory allocation fails or -ENOSPC if * there is no more space in the XArray. diff --git a/lib/xarray.c b/lib/xarray.c index c3e2084aa313..7946380cd6c9 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -610,8 +610,8 @@ static int xas_expand(struct xa_state *xas, void *head) * (see the xa_cmpxchg() implementation for an example). * * Return: If the slot already existed, returns the contents of this slot. - * If the slot was newly created, returns NULL. If it failed to create the - * slot, returns NULL and indicates the error in @xas. + * If the slot was newly created, returns %NULL. If it failed to create the + * slot, returns %NULL and indicates the error in @xas. */ static void *xas_create(struct xa_state *xas) { @@ -1640,7 +1640,7 @@ EXPORT_SYMBOL(__xa_alloc); * @index: Index of entry. * @mark: Mark number. * - * Attempting to set a mark on a NULL entry does not succeed. + * Attempting to set a mark on a %NULL entry does not succeed. * * Context: Any context. Expects xa_lock to be held on entry. */ @@ -1710,7 +1710,7 @@ EXPORT_SYMBOL(xa_get_mark); * @index: Index of entry. * @mark: Mark number. * - * Attempting to set a mark on a NULL entry does not succeed. + * Attempting to set a mark on a %NULL entry does not succeed. * * Context: Process context. Takes and releases the xa_lock. */ @@ -1879,7 +1879,7 @@ static unsigned int xas_extract_marked(struct xa_state *xas, void **dst, * * The @filter may be an XArray mark value, in which case entries which are * marked with that mark will be copied. It may also be %XA_PRESENT, in - * which case all entries which are not NULL will be copied. + * which case all entries which are not %NULL will be copied. * * The entries returned may not represent a snapshot of the XArray at a * moment in time. For example, if another thread stores to index 5, then From 44a4a66b619a0a83a52e707ebcd80182207bd50e Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 5 Nov 2018 10:53:09 -0500 Subject: [PATCH 11/19] XArray: Correct xa_store_range The explicit '64' should have been BITS_PER_LONG, but while looking at this code I realised I meant to use __ffs(), not ilog2(). Signed-off-by: Matthew Wilcox --- lib/xarray.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/lib/xarray.c b/lib/xarray.c index 7946380cd6c9..bbacca576593 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1565,8 +1565,9 @@ void *xa_store_range(struct xarray *xa, unsigned long first, do { xas_lock(&xas); if (entry) { - unsigned int order = (last == ~0UL) ? 64 : - ilog2(last + 1); + unsigned int order = BITS_PER_LONG; + if (last + 1) + order = __ffs(last + 1); xas_set_order(&xas, last, order); xas_create(&xas); if (xas_error(&xas)) From 5404a7f1c21cfda061712bedf2d06cc0f6c755e9 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 5 Nov 2018 09:34:04 -0500 Subject: [PATCH 12/19] XArray tests: Correct some 64-bit assumptions The test-suite caught these two mistakes when compiled for 32-bit. I had only been running the test-suite in 64-bit mode. Signed-off-by: Matthew Wilcox --- lib/test_xarray.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/test_xarray.c b/lib/test_xarray.c index e5294b20b52f..5f9c14e975a4 100644 --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -504,7 +504,7 @@ static noinline void check_multi_store(struct xarray *xa) rcu_read_unlock(); /* We can erase multiple values with a single store */ - xa_store_order(xa, 0, 63, NULL, GFP_KERNEL); + xa_store_order(xa, 0, BITS_PER_LONG - 1, NULL, GFP_KERNEL); XA_BUG_ON(xa, !xa_empty(xa)); /* Even when the first slot is empty but the others aren't */ @@ -1101,7 +1101,7 @@ static noinline void check_store_range(struct xarray *xa) __check_store_range(xa, 4095 + i, 4095 + j); __check_store_range(xa, 4096 + i, 4096 + j); __check_store_range(xa, 123456 + i, 123456 + j); - __check_store_range(xa, UINT_MAX + i, UINT_MAX + j); + __check_store_range(xa, (1 << 24) + i, (1 << 24) + j); } } } From 6d7cd8c1373746a93dc868ee9d38a82df78b38aa Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 6 Nov 2018 13:11:57 -0500 Subject: [PATCH 13/19] dax: Remove optimisation from dax_lock_mapping_entry Skipping some of the revalidation after we sleep can lead to returning a mapping which has already been freed. Just drop this optimisation. Reported-by: Dan Williams Fixes: 9f32d221301c ("dax: Convert dax_lock_mapping_entry to XArray") Signed-off-by: Matthew Wilcox --- fs/dax.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 616e36ea6aaa..529ac9d7c10a 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -383,11 +383,8 @@ bool dax_lock_mapping_entry(struct page *page) entry = xas_load(&xas); if (dax_is_locked(entry)) { entry = get_unlocked_entry(&xas); - /* Did the page move while we slept? */ - if (dax_to_pfn(entry) != page_to_pfn(page)) { - xas_unlock_irq(&xas); - continue; - } + xas_unlock_irq(&xas); + continue; } dax_lock_entry(&xas, entry); xas_unlock_irq(&xas); From 7ae2ea7dc45e8250a74cfaaecdce578427669ae5 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 9 Nov 2018 20:09:37 -0500 Subject: [PATCH 14/19] dax: Make sure the unlocking entry isn't locked I wrote the semantics in the commit message, but didn't document it in the source code. Use a BUG_ON instead (if any code does do this, it's really buggy; we can't recover and it's worth taking the machine down). Signed-off-by: Matthew Wilcox --- fs/dax.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/dax.c b/fs/dax.c index 529ac9d7c10a..7944417f5a71 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -255,6 +255,7 @@ static void dax_unlock_entry(struct xa_state *xas, void *entry) { void *old; + BUG_ON(dax_is_locked(entry)); xas_reset(xas); xas_lock_irq(xas); old = xas_store(xas, entry); From c5bbd4515a05f8acb7e6ab6297044a529762cbf5 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 16 Nov 2018 14:37:06 -0500 Subject: [PATCH 15/19] dax: Reinstate RCU protection of inode For the device-dax case, it is possible that the inode can go away underneath us. The rcu_read_lock() was there to prevent it from being freed, and not (as I thought) to protect the tree. Bring back the rcu_read_lock() protection. Also add a little kernel-doc; while this function is not exported to modules, it is used from outside dax.c Reported-by: Dan Williams Fixes: 9f32d221301c ("dax: Convert dax_lock_mapping_entry to XArray") Signed-off-by: Matthew Wilcox --- fs/dax.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 7944417f5a71..ce87d21b3805 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -353,16 +353,27 @@ static struct page *dax_busy_page(void *entry) return NULL; } +/* + * dax_lock_mapping_entry - Lock the DAX entry corresponding to a page + * @page: The page whose entry we want to lock + * + * Context: Process context. + * Return: %true if the entry was locked or does not need to be locked. + */ bool dax_lock_mapping_entry(struct page *page) { XA_STATE(xas, NULL, 0); void *entry; + bool locked; + /* Ensure page->mapping isn't freed while we look at it */ + rcu_read_lock(); for (;;) { struct address_space *mapping = READ_ONCE(page->mapping); + locked = false; if (!dax_mapping(mapping)) - return false; + break; /* * In the device-dax case there's no need to lock, a @@ -371,8 +382,9 @@ bool dax_lock_mapping_entry(struct page *page) * otherwise we would not have a valid pfn_to_page() * translation. */ + locked = true; if (S_ISCHR(mapping->host->i_mode)) - return true; + break; xas.xa = &mapping->i_pages; xas_lock_irq(&xas); @@ -383,14 +395,18 @@ bool dax_lock_mapping_entry(struct page *page) xas_set(&xas, page->index); entry = xas_load(&xas); if (dax_is_locked(entry)) { + rcu_read_unlock(); entry = get_unlocked_entry(&xas); xas_unlock_irq(&xas); + rcu_read_lock(); continue; } dax_lock_entry(&xas, entry); xas_unlock_irq(&xas); - return true; + break; } + rcu_read_unlock(); + return locked; } void dax_unlock_mapping_entry(struct page *page) From fda490d39fc0668d92e170d95c11e35a010019aa Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 16 Nov 2018 15:07:31 -0500 Subject: [PATCH 16/19] dax: Fix dax_unlock_mapping_entry for PMD pages Device DAX PMD pages do not set the PageHead bit for compound pages. Fix for now by retrieving the PMD bit from the entry, but eventually we will be passed the page size by the caller. Reported-by: Dan Williams Fixes: 9f32d221301c ("dax: Convert dax_lock_mapping_entry to XArray") Signed-off-by: Matthew Wilcox --- fs/dax.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index ce87d21b3805..5426252375f6 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -98,12 +98,6 @@ static void *dax_make_entry(pfn_t pfn, unsigned long flags) return xa_mk_value(flags | (pfn_t_to_pfn(pfn) << DAX_SHIFT)); } -static void *dax_make_page_entry(struct page *page) -{ - pfn_t pfn = page_to_pfn_t(page); - return dax_make_entry(pfn, PageHead(page) ? DAX_PMD : 0); -} - static bool dax_is_locked(void *entry) { return xa_to_value(entry) & DAX_LOCKED; @@ -116,12 +110,12 @@ static unsigned int dax_entry_order(void *entry) return 0; } -static int dax_is_pmd_entry(void *entry) +static unsigned long dax_is_pmd_entry(void *entry) { return xa_to_value(entry) & DAX_PMD; } -static int dax_is_pte_entry(void *entry) +static bool dax_is_pte_entry(void *entry) { return !(xa_to_value(entry) & DAX_PMD); } @@ -413,11 +407,16 @@ void dax_unlock_mapping_entry(struct page *page) { struct address_space *mapping = page->mapping; XA_STATE(xas, &mapping->i_pages, page->index); + void *entry; if (S_ISCHR(mapping->host->i_mode)) return; - dax_unlock_entry(&xas, dax_make_page_entry(page)); + rcu_read_lock(); + entry = xas_load(&xas); + rcu_read_unlock(); + entry = dax_make_entry(page_to_pfn_t(page), dax_is_pmd_entry(entry)); + dax_unlock_entry(&xas, entry); } /* From 0e40de0338d005f73d46898a21544cd26f01b4ce Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 16 Nov 2018 15:19:13 -0500 Subject: [PATCH 17/19] dax: Fix huge page faults Using xas_load() with a PMD-sized xa_state would work if either a PMD-sized entry was present or a PTE sized entry was present in the first 64 entries (of the 512 PTEs in a PMD on x86). If there was no PTE in the first 64 entries, grab_mapping_entry() would believe there were no entries present, allocate a PMD-sized entry and overwrite the PTE in the page cache. Use xas_find_conflict() instead which turns out to simplify both get_unlocked_entry() and grab_mapping_entry(). Also remove a WARN_ON_ONCE from grab_mapping_entry() as it will have already triggered in get_unlocked_entry(). Fixes: cfc93c6c6c96 ("dax: Convert dax_insert_pfn_mkwrite to XArray") Signed-off-by: Matthew Wilcox --- fs/dax.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 5426252375f6..cf2394e2bf4b 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -216,9 +216,8 @@ static void *get_unlocked_entry(struct xa_state *xas) ewait.wait.func = wake_exceptional_entry_func; for (;;) { - entry = xas_load(xas); - if (!entry || xa_is_internal(entry) || - WARN_ON_ONCE(!xa_is_value(entry)) || + entry = xas_find_conflict(xas); + if (!entry || WARN_ON_ONCE(!xa_is_value(entry)) || !dax_is_locked(entry)) return entry; @@ -458,11 +457,9 @@ static void *grab_mapping_entry(struct xa_state *xas, retry: xas_lock_irq(xas); entry = get_unlocked_entry(xas); - if (xa_is_internal(entry)) - goto fallback; if (entry) { - if (WARN_ON_ONCE(!xa_is_value(entry))) { + if (!xa_is_value(entry)) { xas_set_err(xas, EIO); goto out_unlock; } @@ -1641,8 +1638,7 @@ dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order) /* Did we race with someone splitting entry or so? */ if (!entry || (order == 0 && !dax_is_pte_entry(entry)) || - (order == PMD_ORDER && (xa_is_internal(entry) || - !dax_is_pmd_entry(entry)))) { + (order == PMD_ORDER && !dax_is_pmd_entry(entry))) { put_unlocked_entry(&xas, entry); xas_unlock_irq(&xas); trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf, From 25bbe21bf427a81b8e3ccd480ea0e1d940256156 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 16 Nov 2018 15:50:02 -0500 Subject: [PATCH 18/19] dax: Avoid losing wakeup in dax_lock_mapping_entry After calling get_unlocked_entry(), you have to call put_unlocked_entry() to avoid subsequent waiters losing wakeups. Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()") Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox --- fs/dax.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/dax.c b/fs/dax.c index cf2394e2bf4b..9bcce89ea18e 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -391,6 +391,7 @@ bool dax_lock_mapping_entry(struct page *page) rcu_read_unlock(); entry = get_unlocked_entry(&xas); xas_unlock_irq(&xas); + put_unlocked_entry(&xas, entry); rcu_read_lock(); continue; } From fffc9a260e38acec3187515738122a3ecb24ac90 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Mon, 19 Nov 2018 09:36:29 -0500 Subject: [PATCH 19/19] XArray tests: Add missing locking Lockdep caught me being sloppy in the test suite and failing to lock the XArray appropriately. Reported-by: kernel test robot Signed-off-by: Matthew Wilcox --- lib/test_xarray.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/lib/test_xarray.c b/lib/test_xarray.c index 5f9c14e975a4..0598e86af8fc 100644 --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -208,15 +208,19 @@ static noinline void check_xa_mark_1(struct xarray *xa, unsigned long index) XA_BUG_ON(xa, xa_get_mark(xa, i, XA_MARK_2)); /* We should see two elements in the array */ + rcu_read_lock(); xas_for_each(&xas, entry, ULONG_MAX) seen++; + rcu_read_unlock(); XA_BUG_ON(xa, seen != 2); /* One of which is marked */ xas_set(&xas, 0); seen = 0; + rcu_read_lock(); xas_for_each_marked(&xas, entry, ULONG_MAX, XA_MARK_0) seen++; + rcu_read_unlock(); XA_BUG_ON(xa, seen != 1); } XA_BUG_ON(xa, xa_get_mark(xa, next, XA_MARK_0)); @@ -442,7 +446,9 @@ static noinline void check_multi_store_1(struct xarray *xa, unsigned long index, XA_BUG_ON(xa, xa_load(xa, max) != NULL); XA_BUG_ON(xa, xa_load(xa, min - 1) != NULL); + xas_lock(&xas); XA_BUG_ON(xa, xas_store(&xas, xa_mk_value(min)) != xa_mk_value(index)); + xas_unlock(&xas); XA_BUG_ON(xa, xa_load(xa, min) != xa_mk_value(min)); XA_BUG_ON(xa, xa_load(xa, max - 1) != xa_mk_value(min)); XA_BUG_ON(xa, xa_load(xa, max) != NULL); @@ -458,9 +464,11 @@ static noinline void check_multi_store_2(struct xarray *xa, unsigned long index, XA_STATE(xas, xa, index); xa_store_order(xa, index, order, xa_mk_value(0), GFP_KERNEL); + xas_lock(&xas); XA_BUG_ON(xa, xas_store(&xas, xa_mk_value(1)) != xa_mk_value(0)); XA_BUG_ON(xa, xas.xa_index != index); XA_BUG_ON(xa, xas_store(&xas, NULL) != xa_mk_value(1)); + xas_unlock(&xas); XA_BUG_ON(xa, !xa_empty(xa)); } #endif @@ -1180,10 +1188,12 @@ static noinline void check_account(struct xarray *xa) XA_STATE(xas, xa, 1 << order); xa_store_order(xa, 0, order, xa, GFP_KERNEL); + rcu_read_lock(); xas_load(&xas); XA_BUG_ON(xa, xas.xa_node->count == 0); XA_BUG_ON(xa, xas.xa_node->count > (1 << order)); XA_BUG_ON(xa, xas.xa_node->nr_values != 0); + rcu_read_unlock(); xa_store_order(xa, 1 << order, order, xa_mk_value(1 << order), GFP_KERNEL);