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XArray: Add xa_for_each_range

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This function supports iterating over a range of an array.  Also add
documentation links for xa_for_each_start().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-01-12 15:54:10 -05:00
parent c44aa5e8ab
commit 00ed452c21
2 changed files with 38 additions and 9 deletions
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10
Documentation/core-api/xarray.rst
View File

@ -82,10 +82,10 @@ at that index is ``NULL``, you can use xa_insert() which
returns ``-EBUSY`` if the entry is not empty.
You can copy entries out of the XArray into a plain array by calling
xa_extract(). Or you can iterate over the present entries in
the XArray by calling xa_for_each(). You may prefer to use
xa_find() or xa_find_after() to move to the next present
entry in the XArray.
xa_extract(). Or you can iterate over the present entries in the XArray
by calling xa_for_each(), xa_for_each_start() or xa_for_each_range().
You may prefer to use xa_find() or xa_find_after() to move to the next
present entry in the XArray.
Calling xa_store_range() stores the same entry in a range
of indices. If you do this, some of the other operations will behave
@ -193,6 +193,8 @@ No lock needed:
Takes RCU read lock:
* xa_load()
* xa_for_each()
* xa_for_each_start()
* xa_for_each_range()
* xa_find()
* xa_find_after()
* xa_extract()

37
include/linux/xarray.h
View File

@ -416,6 +416,36 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
return xa->xa_flags & XA_FLAGS_MARK(mark);
}
/**
* xa_for_each_range() - Iterate over a portion of an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
* @start: First index to retrieve from array.
* @last: Last index to retrieve from array.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index. You may modify @index during the iteration if you
* want to skip or reprocess indices. It is safe to modify the array
* during the iteration. At the end of the iteration, @entry will be set
* to NULL and @index will have a value less than or equal to max.
*
* xa_for_each_range() is O(n.log(n)) while xas_for_each() is O(n). You have
* to handle your own locking with xas_for_each(), and if you have to unlock
* after each iteration, it will also end up being O(n.log(n)).
* xa_for_each_range() will spin if it hits a retry entry; if you intend to
* see retry entries, you should use the xas_for_each() iterator instead.
* The xas_for_each() iterator will expand into more inline code than
* xa_for_each_range().
*
* Context: Any context. Takes and releases the RCU lock.
*/
#define xa_for_each_range(xa, index, entry, start, last) \
for (index = start, \
entry = xa_find(xa, &index, last, XA_PRESENT); \
entry; \
entry = xa_find_after(xa, &index, last, XA_PRESENT))
/**
* xa_for_each_start() - Iterate over a portion of an XArray.
* @xa: XArray.
@ -439,11 +469,8 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
*
* Context: Any context. Takes and releases the RCU lock.
*/
#define xa_for_each_start(xa, index, entry, start) \
for (index = start, \
entry = xa_find(xa, &index, ULONG_MAX, XA_PRESENT); \
entry; \
entry = xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT))
#define xa_for_each_start(xa, index, entry, start) \
xa_for_each_range(xa, index, entry, start, ULONG_MAX)
/**
* xa_for_each() - Iterate over present entries in an XArray.