From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753883AbdLFAv0 (ORCPT ); Tue, 5 Dec 2017 19:51:26 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:36318 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753364AbdLFAmO (ORCPT ); Tue, 5 Dec 2017 19:42:14 -0500 From: Matthew Wilcox Cc: Matthew Wilcox , Ross Zwisler , Jens Axboe , Rehas Sachdeva , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-nilfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 15/73] xarray: Add xa_get_entries, xa_get_tagged and xa_get_maybe_tag Date: Tue, 5 Dec 2017 16:41:01 -0800 Message-Id: <20171206004159.3755-16-willy@infradead.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20171206004159.3755-1-willy@infradead.org> References: <20171206004159.3755-1-willy@infradead.org> To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Matthew Wilcox These functions allow a range of xarray entries to be extracted into a compact normal array. Signed-off-by: Matthew Wilcox --- include/linux/xarray.h | 27 ++++++++++++++++ lib/xarray.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 115 insertions(+) diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 4e61ebd406f5..c3efcc3432f7 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -135,6 +135,33 @@ void *xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t); void *xa_find(struct xarray *xa, unsigned long *index, unsigned long max); void *xa_find_after(struct xarray *xa, unsigned long *index, unsigned long max); +int xa_get_entries(struct xarray *, void **dst, unsigned long start, + unsigned long max, unsigned int n); +int xa_get_tagged(struct xarray *, void **dst, unsigned long start, + unsigned long max, unsigned int n, xa_tag_t); + +/** + * xa_get_maybe_tag() - Copy entries from the XArray into a normal array. + * @xa: The source XArray to copy from. + * @dst: The buffer to copy pointers into. + * @start: The first index in the XArray eligible to be copied from. + * @max: The last index in the XArray eligible to be copied from. + * @n: The maximum number of entries to copy. + * @tag: Tag number. + * + * If you specify %XA_NO_TAG as the tag number, this is the same as + * xa_get_entries(). Otherwise, it is the same as xa_get_tagged(). + * + * Return: The number of entries copied. + */ +static inline int xa_get_maybe_tag(struct xarray *xa, void **dst, + unsigned long start, unsigned long max, + unsigned int n, xa_tag_t tag) +{ + if (tag == XA_NO_TAG) + return xa_get_entries(xa, dst, start, max, n); + return xa_get_tagged(xa, dst, start, max, n, tag); +} /** * xa_for_each() - Iterate over a portion of an XArray. diff --git a/lib/xarray.c b/lib/xarray.c index f9eaac2d85f9..251724f62b11 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1253,6 +1253,94 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp, unsigned long max) } EXPORT_SYMBOL(xa_find_after); +/** + * xa_get_entries() - Copy entries from the XArray into a normal array. + * @xa: The source XArray to copy from. + * @dst: The buffer to copy pointers into. + * @start: The first index in the XArray eligible to be copied from. + * @max: The last index in the XArray eligible to be copied from. + * @n: The maximum number of entries to copy. + * + * Copies up to @n non-NULL entries from the XArray. The copied entries will + * have indices between @start and @max, inclusive. + * + * This function uses the RCU lock to protect itself. That means that the + * entries returned may not represent a snapshot of the XArray at a moment + * in time. For example, if index 5 is stored to, then index 10 is stored to, + * calling xa_get_entries() may return the old contents of index 5 and the + * new contents of index 10. Indices not modified while this function is + * running will not be skipped. + * + * If you need stronger guarantees, holding the xa_lock across calls to this + * function will prevent concurrent modification. + * + * Return: The number of entries copied. + */ +int xa_get_entries(struct xarray *xa, void **dst, unsigned long start, + unsigned long max, unsigned int n) +{ + XA_STATE(xas, xa, start); + void *entry; + unsigned int i = 0; + + if (!n) + return 0; + + rcu_read_lock(); + xas_for_each(&xas, entry, max) { + if (xas_retry(&xas, entry)) + continue; + dst[i++] = entry; + if (i == n) + break; + } + rcu_read_unlock(); + + return i; +} +EXPORT_SYMBOL(xa_get_entries); + +/** + * xa_get_tagged() - Copy tagged entries from the XArray into a normal array. + * @xa: The source XArray to copy from. + * @dst: The buffer to copy pointers into. + * @start: The first index in the XArray eligible to be copied from. + * @max: The last index in the XArray eligible to be copied from + * @n: The maximum number of entries to copy. + * @tag: Tag number. + * + * Copies up to @n non-NULL entries that have @tag set from the XArray. The + * copied entries will have indices between @start and @max, inclusive. + * + * See the xa_get_entries() documentation for the consistency guarantees + * provided. + * + * Return: The number of entries copied. + */ +int xa_get_tagged(struct xarray *xa, void **dst, unsigned long start, + unsigned long max, unsigned int n, xa_tag_t tag) +{ + XA_STATE(xas, xa, start); + void *entry; + unsigned int i = 0; + + if (!n) + return 0; + + rcu_read_lock(); + xas_for_each_tag(&xas, entry, max, tag) { + if (xas_retry(&xas, entry)) + continue; + dst[i++] = entry; + if (i == n) + break; + } + rcu_read_unlock(); + + return i; +} +EXPORT_SYMBOL(xa_get_tagged); + #ifdef XA_DEBUG void xa_dump_entry(void *entry, unsigned long index) { -- 2.15.0