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XArray: Add xa_cmpxchg_irq and xa_cmpxchg_bh

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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: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox 2018-11-26 16:08:43 -05:00
parent eff3860bbf
commit 55f3f7eab7
3 changed files with 59 additions and 4 deletions
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5
Documentation/core-api/xarray.rst
View File

@ -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

54
include/linux/xarray.h
View File

@ -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.

4
mm/shmem.c
View File

@ -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));