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XArray: Honour reserved entries in xa_insert

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xa_insert() should treat reserved entries as occupied, not as available.
Also, it should treat requests to insert a NULL pointer as a request
to reserve the slot.  Add xa_insert_bh() and xa_insert_irq() for
completeness.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox
2019-01-02 13:57:03 -05:00
parent 76b4e52995
commit b0606fed6e
4 changed files with 126 additions and 48 deletions
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15
Documentation/core-api/xarray.rst
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@@ -108,12 +108,13 @@ some, but not all of the other indices changing.
Sometimes you need to ensure that a subsequent call to :c:func:`xa_store`
will not need to allocate memory. The :c:func:`xa_reserve` function
will store a reserved entry at the indicated index. Users of the normal
API will see this entry as containing ``NULL``. If you do not need to
use the reserved entry, you can call :c:func:`xa_release` to remove the
unused entry. If another user has stored to the entry in the meantime,
:c:func:`xa_release` will do nothing; if instead you want the entry to
become ``NULL``, you should use :c:func:`xa_erase`.
will store a reserved entry at the indicated index. Users of the
normal API will see this entry as containing ``NULL``. If you do
not need to use the reserved entry, you can call :c:func:`xa_release`
to remove the unused entry. If another user has stored to the entry
in the meantime, :c:func:`xa_release` will do nothing; if instead you
want the entry to become ``NULL``, you should use :c:func:`xa_erase`.
Using :c:func:`xa_insert` on a reserved entry will fail.
If all entries in the array are ``NULL``, the :c:func:`xa_empty` function
will return ``true``.
@@ -183,6 +184,8 @@ Takes xa_lock internally:
* :c:func:`xa_store_bh`
* :c:func:`xa_store_irq`
* :c:func:`xa_insert`
* :c:func:`xa_insert_bh`
* :c:func:`xa_insert_irq`
* :c:func:`xa_erase`
* :c:func:`xa_erase_bh`
* :c:func:`xa_erase_irq`