From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: [PATCH v5 16/78] xarray: Add xa_get_entries, xa_get_tagged and xa_get_maybe_tag Date: Fri, 15 Dec 2017 14:03:48 -0800 Message-ID: <20171215220450.7899-17-willy@infradead.org> References: <20171215220450.7899-1-willy@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sfi-mx-2.v28.ch3.sourceforge.com ([172.29.28.192] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ePy7W-0002qx-AR for linux-f2fs-devel@lists.sourceforge.net; Fri, 15 Dec 2017 22:06:18 +0000 Received: from bombadil.infradead.org ([65.50.211.133]) by sfi-mx-2.v28.ch3.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) id 1ePy7V-0007FH-5d for linux-f2fs-devel@lists.sourceforge.net; Fri, 15 Dec 2017 22:06:18 +0000 In-Reply-To: <20171215220450.7899-1-willy@infradead.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: linux-kernel@vger.kernel.org Cc: Jens Axboe , linux-xfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-raid@vger.kernel.org, Matthew Wilcox , Marc Zyngier , linux-usb@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, David Howells , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Ross Zwisler , Rehas Sachdeva , Shaohua Li , linux-btrfs@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 85a319463e46..1367d694eebd 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -140,6 +140,33 @@ 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 9ac1e9730c24..e73ae7b57fc9 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1330,6 +1330,94 @@ 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_node(const struct xa_node *node) { -- 2.15.1 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot