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authorLinus Torvalds <torvalds@linux-foundation.org>2019-03-12 06:06:18 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-12 06:06:18 +0300
commitea295481b6e313b4ea3ca2720ffcafd6005b5643 (patch)
tree85cade73987615fb5d86acdf2c7eac0a0378e255 /Documentation/core-api
parentf3124ccf025caf25b764d900d1f9c49731673e49 (diff)
parent4a5c8d898948d1ac876522cdd62f07a78104bfe9 (diff)
downloadlinux-ea295481b6e313b4ea3ca2720ffcafd6005b5643.tar.xz
Merge tag 'xarray-5.1-rc1' of git://git.infradead.org/users/willy/linux-dax
Pull XArray updates from Matthew Wilcox: "This pull request changes the xa_alloc() API. I'm only aware of one subsystem that has started trying to use it, and we agree on the fixup as part of the merge. The xa_insert() error code also changed to match xa_alloc() (EEXIST to EBUSY), and I added xa_alloc_cyclic(). Beyond that, the usual bugfixes, optimisations and tweaking. I now have a git tree with all users of the radix tree and IDR converted over to the XArray that I'll be feeding to maintainers over the next few weeks" * tag 'xarray-5.1-rc1' of git://git.infradead.org/users/willy/linux-dax: XArray: Fix xa_reserve for 2-byte aligned entries XArray: Fix xa_erase of 2-byte aligned entries XArray: Use xa_cmpxchg to implement xa_reserve XArray: Fix xa_release in allocating arrays XArray: Mark xa_insert and xa_reserve as must_check XArray: Add cyclic allocation XArray: Redesign xa_alloc API XArray: Add support for 1s-based allocation XArray: Change xa_insert to return -EBUSY XArray: Update xa_erase family descriptions XArray tests: RCU lock prohibits GFP_KERNEL
Diffstat (limited to 'Documentation/core-api')
-rw-r--r--Documentation/core-api/xarray.rst15
1 files changed, 10 insertions, 5 deletions
diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst
index 5d54b27c6eba..ef6f9f98f595 100644
--- a/Documentation/core-api/xarray.rst
+++ b/Documentation/core-api/xarray.rst
@@ -85,7 +85,7 @@ which was at that index; if it returns the same entry which was passed as
If you want to only store a new entry to an index if the current entry
at that index is ``NULL``, you can use :c:func:`xa_insert` which
-returns ``-EEXIST`` if the entry is not empty.
+returns ``-EBUSY`` if the entry is not empty.
You can enquire whether a mark is set on an entry by using
:c:func:`xa_get_mark`. If the entry is not ``NULL``, you can set a mark
@@ -131,17 +131,23 @@ If you use :c:func:`DEFINE_XARRAY_ALLOC` to define the XArray, or
initialise it by passing ``XA_FLAGS_ALLOC`` to :c:func:`xa_init_flags`,
the XArray changes to track whether entries are in use or not.
-You can call :c:func:`xa_alloc` to store the entry at any unused index
+You can call :c:func:`xa_alloc` to store the entry at an unused index
in the XArray. If you need to modify the array from interrupt context,
you can use :c:func:`xa_alloc_bh` or :c:func:`xa_alloc_irq` to disable
interrupts while allocating the ID.
-Using :c:func:`xa_store`, :c:func:`xa_cmpxchg` or :c:func:`xa_insert`
-will mark the entry as being allocated. Unlike a normal XArray, storing
+Using :c:func:`xa_store`, :c:func:`xa_cmpxchg` or :c:func:`xa_insert` will
+also mark the entry as being allocated. Unlike a normal XArray, storing
``NULL`` will mark the entry as being in use, like :c:func:`xa_reserve`.
To free an entry, use :c:func:`xa_erase` (or :c:func:`xa_release` if
you only want to free the entry if it's ``NULL``).
+By default, the lowest free entry is allocated starting from 0. If you
+want to allocate entries starting at 1, it is more efficient to use
+:c:func:`DEFINE_XARRAY_ALLOC1` or ``XA_FLAGS_ALLOC1``. If you want to
+allocate IDs up to a maximum, then wrap back around to the lowest free
+ID, you can use :c:func:`xa_alloc_cyclic`.
+
You cannot use ``XA_MARK_0`` with an allocating XArray as this mark
is used to track whether an entry is free or not. The other marks are
available for your use.
@@ -209,7 +215,6 @@ Assumes xa_lock held on entry:
* :c:func:`__xa_erase`
* :c:func:`__xa_cmpxchg`
* :c:func:`__xa_alloc`
- * :c:func:`__xa_reserve`
* :c:func:`__xa_set_mark`
* :c:func:`__xa_clear_mark`