Commit 55f3f7ea authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

XArray: Add xa_cmpxchg_irq and xa_cmpxchg_bh 



These convenience wrappers match the other _irq and _bh wrappers we
already have.  It turns out I'd already open-coded xa_cmpxchg_irq()
in the shmem code, so convert that.

Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
parent eff3860b

Documentation/core-api/xarray.rst

+4 −1
Original line number Diff line number Diff line
@@ -187,6 +187,8 @@ Takes xa_lock internally: 
 * :c:func:`xa_erase_bh`

 * :c:func:`xa_erase_irq`

 * :c:func:`xa_cmpxchg`

 * :c:func:`xa_cmpxchg_bh`

 * :c:func:`xa_cmpxchg_irq`

 * :c:func:`xa_store_range`

 * :c:func:`xa_alloc`

 * :c:func:`xa_alloc_bh`
@@ -263,7 +265,8 @@ using :c:func:`xa_lock_irqsave` in both the interrupt handler and process 
context, or :c:func:`xa_lock_irq` in process context and :c:func:`xa_lock`

in the interrupt handler.  Some of the more common patterns have helper

functions such as :c:func:`xa_store_bh`, :c:func:`xa_store_irq`,

:c:func:`xa_erase_bh` and :c:func:`xa_erase_irq`.

:c:func:`xa_erase_bh`, :c:func:`xa_erase_irq`, :c:func:`xa_cmpxchg_bh`

and :c:func:`xa_cmpxchg_irq`.



Sometimes you need to protect access to the XArray with a mutex because

that lock sits above another mutex in the locking hierarchy.  That does

include/linux/xarray.h

+54 −0
Original line number Diff line number Diff line
@@ -553,6 +553,60 @@ static inline void *xa_cmpxchg(struct xarray *xa, unsigned long index, 
	return curr;

}



/**

 * xa_cmpxchg_bh() - Conditionally replace an entry in the XArray.

 * @xa: XArray.

 * @index: Index into array.

 * @old: Old value to test against.

 * @entry: New value to place in array.

 * @gfp: Memory allocation flags.

 *

 * This function is like calling xa_cmpxchg() except it disables softirqs

 * while holding the array lock.

 *

 * Context: Any context.  Takes and releases the xa_lock while

 * disabling softirqs.  May sleep if the @gfp flags permit.

 * Return: The old value at this index or xa_err() if an error happened.

 */

static inline void *xa_cmpxchg_bh(struct xarray *xa, unsigned long index,

			void *old, void *entry, gfp_t gfp)

{

	void *curr;



	xa_lock_bh(xa);

	curr = __xa_cmpxchg(xa, index, old, entry, gfp);

	xa_unlock_bh(xa);



	return curr;

}



/**

 * xa_cmpxchg_irq() - Conditionally replace an entry in the XArray.

 * @xa: XArray.

 * @index: Index into array.

 * @old: Old value to test against.

 * @entry: New value to place in array.

 * @gfp: Memory allocation flags.

 *

 * This function is like calling xa_cmpxchg() except it disables interrupts

 * while holding the array lock.

 *

 * Context: Process context.  Takes and releases the xa_lock while

 * disabling interrupts.  May sleep if the @gfp flags permit.

 * Return: The old value at this index or xa_err() if an error happened.

 */

static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,

			void *old, void *entry, gfp_t gfp)

{

	void *curr;



	xa_lock_irq(xa);

	curr = __xa_cmpxchg(xa, index, old, entry, gfp);

	xa_unlock_irq(xa);



	return curr;

}



/**

 * xa_insert() - Store this entry in the XArray unless another entry is

 *			already present.

mm/shmem.c

+1 −3
Original line number Diff line number Diff line
@@ -661,9 +661,7 @@ static int shmem_free_swap(struct address_space *mapping, 
{

	void *old;



	xa_lock_irq(&mapping->i_pages);

	old = __xa_cmpxchg(&mapping->i_pages, index, radswap, NULL, 0);

	xa_unlock_irq(&mapping->i_pages);

	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);

	if (old != radswap)

		return -ENOENT;

	free_swap_and_cache(radix_to_swp_entry(radswap));