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 01/12] list.h: add list_pop and list_pop_entry helpers
Date: Mon, 22 Jul 2019 11:50:13 +0200 [thread overview]
Message-ID: <20190722095024.19075-2-hch@lst.de> (raw)
In-Reply-To: <20190722095024.19075-1-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 85c92555e31f..d3b00267446a 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -514,6 +514,39 @@ 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:[~2019-07-22 9:50 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-22 9:50 lift the xfs writepage code into iomap v3 Christoph Hellwig
2019-07-22 9:50 ` Christoph Hellwig [this message]
2019-07-22 20:12 ` [PATCH 01/12] list.h: add list_pop and list_pop_entry helpers Matthew Wilcox
2019-07-22 9:50 ` [PATCH 02/12] xfs: initialize iomap->flags in xfs_bmbt_to_iomap Christoph Hellwig
2019-07-22 9:50 ` [PATCH 03/12] xfs: use a struct iomap in xfs_writepage_ctx Christoph Hellwig
2019-07-22 9:50 ` [PATCH 04/12] xfs: refactor the ioend merging code Christoph Hellwig
2019-07-22 9:50 ` [PATCH 05/12] xfs: turn io_append_trans into an io_private void pointer Christoph Hellwig
2019-07-22 9:50 ` [PATCH 06/12] xfs: remove the fork fields in the writepage_ctx and ioend Christoph Hellwig
2019-07-22 9:50 ` [PATCH 07/12] iomap: move the xfs writeback code to iomap.c Christoph Hellwig
2019-07-22 9:50 ` [PATCH 08/12] iomap: add tracing for the address space operations Christoph Hellwig
2019-07-22 9:50 ` [PATCH 09/12] iomap: move struct iomap_page out of iomap.h Christoph Hellwig
2019-07-22 9:50 ` [PATCH 10/12] iomap: warn on inline maps in iomap_writepage_map Christoph Hellwig
2019-07-22 9:50 ` [PATCH 11/12] xfs: set IOMAP_F_NEW more carefully Christoph Hellwig
2019-07-22 9:50 ` [PATCH 12/12] iomap: zero newly allocated mapped blocks Christoph Hellwig
2019-07-22 20:12 ` lift the xfs writepage code into iomap v3 Andreas Gruenbacher
2019-07-26 23:37 ` Darrick J. Wong
2019-07-27 13:33 ` Andreas Gruenbacher
2019-07-29 0:06 ` Darrick J. Wong
2019-07-30 1:17 ` Darrick J. Wong
2019-07-31 6:04 ` Damien Le Moal
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