From: Christoph Hellwig <hch@lst.de>
To: "Darrick J . Wong" <darrick.wong@oracle.com>
Cc: Damien Le Moal <Damien.LeMoal@wdc.com>,
Andreas Gruenbacher <agruenba@redhat.com>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 01/13] list.h: add list_pop and list_pop_entry helpers
Date: Thu, 27 Jun 2019 12:48:24 +0200 [thread overview]
Message-ID: <20190627104836.25446-2-hch@lst.de> (raw)
In-Reply-To: <20190627104836.25446-1-hch@lst.de>
We have a very common pattern where we want to delete the first entry
from a list and return it as the properly typed container structure.
Add two helpers to implement this behavior.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/list.h | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/include/linux/list.h b/include/linux/list.h
index e951228db4b2..ba6e27d2235a 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -500,6 +500,39 @@ static inline void list_splice_tail_init(struct list_head *list,
pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
})
+/**
+ * list_pop - delete the first entry from a list and return it
+ * @list: the list to take the element from.
+ *
+ * Return the list entry after @list. If @list is empty return NULL.
+ */
+static inline struct list_head *list_pop(struct list_head *list)
+{
+ struct list_head *pos = READ_ONCE(list->next);
+
+ if (pos == list)
+ return NULL;
+ list_del(pos);
+ return pos;
+}
+
+/**
+ * list_pop_entry - delete the first entry from a list and return the
+ * containing structure
+ * @list: the list to take the element from.
+ * @type: the type of the struct this is embedded in.
+ * @member: the name of the list_head within the struct.
+ *
+ * Return the containing structure for the list entry after @list. If @list
+ * is empty return NULL.
+ */
+#define list_pop_entry(list, type, member) \
+({ \
+ struct list_head *pos__ = list_pop(list); \
+ \
+ pos__ ? list_entry(pos__, type, member) : NULL; \
+})
+
/**
* list_next_entry - get the next element in list
* @pos: the type * to cursor
--
2.20.1
next prev parent reply other threads:[~2019-06-27 10:49 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-27 10:48 lift the xfs writepage code into iomap v2 Christoph Hellwig
2019-06-27 10:48 ` Christoph Hellwig [this message]
2019-06-27 20:48 ` [PATCH 01/13] list.h: add list_pop and list_pop_entry helpers Darrick J. Wong
2019-06-27 10:48 ` [PATCH 02/13] xfs: remove the unused xfs_count_page_state declaration Christoph Hellwig
2019-06-27 17:50 ` Darrick J. Wong
2019-06-27 10:48 ` [PATCH 03/13] xfs: fix a comment typo in xfs_submit_ioend Christoph Hellwig
2019-06-27 10:48 ` [PATCH 04/13] xfs: initialize iomap->flags in xfs_bmbt_to_iomap Christoph Hellwig
2019-06-27 20:44 ` Darrick J. Wong
2019-06-27 10:48 ` [PATCH 05/13] xfs: use a struct iomap in xfs_writepage_ctx Christoph Hellwig
2019-06-27 10:48 ` [PATCH 06/13] xfs: remove XFS_TRANS_NOFS Christoph Hellwig
2019-06-27 22:30 ` Darrick J. Wong
2019-06-28 5:37 ` Christoph Hellwig
2019-06-28 17:41 ` Darrick J. Wong
2019-06-27 10:48 ` [PATCH 07/13] xfs: allow merging ioends over append boundaries Christoph Hellwig
2019-06-27 18:23 ` Darrick J. Wong
2019-06-27 21:43 ` Luis Chamberlain
2019-06-28 2:52 ` Zorro Lang
2019-06-28 3:33 ` Darrick J. Wong
2019-06-28 5:51 ` Christoph Hellwig
2019-06-28 17:05 ` Darrick J. Wong
2019-06-27 10:48 ` [PATCH 08/13] xfs: simplify xfs_ioend_can_merge Christoph Hellwig
2019-06-27 10:48 ` [PATCH 09/13] xfs: refactor the ioend merging code Christoph Hellwig
2019-06-27 10:48 ` [PATCH 10/13] xfs: turn io_append_trans into an io_private void pointer Christoph Hellwig
2019-06-27 10:48 ` [PATCH 11/13] xfs: remove the fork fields in the writepage_ctx and ioend Christoph Hellwig
2019-06-27 10:48 ` [PATCH 12/13] iomap: move the xfs writeback code to iomap.c Christoph Hellwig
2019-06-27 10:48 ` [PATCH 13/13] iomap: add tracing for the address space operations Christoph Hellwig
2019-06-28 1:32 ` lift the xfs writepage code into iomap v2 Darrick J. Wong
2019-06-28 5:42 ` Christoph Hellwig
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