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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
View File

@ -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`

110
include/linux/xarray.h
View File

@ -463,39 +463,12 @@ void *__xa_erase(struct xarray *, unsigned long index);
void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old,
void *entry, gfp_t);
int __xa_insert(struct xarray *, unsigned long index, void *entry, gfp_t);
int __xa_alloc(struct xarray *, u32 *id, u32 max, void *entry, gfp_t);
int __xa_reserve(struct xarray *, unsigned long index, gfp_t);
void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
/**
* __xa_insert() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* If you would rather see the existing entry in the array, use __xa_cmpxchg().
* This function is for users who don't care what the entry is, only that
* one is present.
*
* Context: Any context. Expects xa_lock to be held on entry. May
* release and reacquire xa_lock if the @gfp flags permit.
* Return: 0 if the store succeeded. -EEXIST if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int __xa_insert(struct xarray *xa, unsigned long index,
void *entry, gfp_t gfp)
{
void *curr = __xa_cmpxchg(xa, index, NULL, entry, gfp);
if (!curr)
return 0;
if (xa_is_err(curr))
return xa_err(curr);
return -EEXIST;
}
/**
* xa_store_bh() - Store this entry in the XArray.
* @xa: XArray.
@ -685,24 +658,83 @@ static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* If you would rather see the existing entry in the array, use xa_cmpxchg().
* This function is for users who don't care what the entry is, only that
* one is present.
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present. Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Process context. Takes and releases the xa_lock.
* May sleep if the @gfp flags permit.
* Context: Any context. Takes and releases the xa_lock. May sleep if
* the @gfp flags permit.
* Return: 0 if the store succeeded. -EEXIST if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int xa_insert(struct xarray *xa, unsigned long index,
void *entry, gfp_t gfp)
{
void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp);
if (!curr)
return 0;
if (xa_is_err(curr))
return xa_err(curr);
return -EEXIST;
int err;
xa_lock(xa);
err = __xa_insert(xa, index, entry, gfp);
xa_unlock(xa);
return err;
}
/**
* xa_insert_bh() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present. Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: 0 if the store succeeded. -EEXIST if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int xa_insert_bh(struct xarray *xa, unsigned long index,
void *entry, gfp_t gfp)
{
int err;
xa_lock_bh(xa);
err = __xa_insert(xa, index, entry, gfp);
xa_unlock_bh(xa);
return err;
}
/**
* xa_insert_irq() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present. Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: 0 if the store succeeded. -EEXIST if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int xa_insert_irq(struct xarray *xa, unsigned long index,
void *entry, gfp_t gfp)
{
int err;
xa_lock_irq(xa);
err = __xa_insert(xa, index, entry, gfp);
xa_unlock_irq(xa);
return err;
}
/**

8
lib/test_xarray.c
View File

@ -382,10 +382,12 @@ static noinline void check_reserve(struct xarray *xa)
xa_erase_index(xa, 12345678);
XA_BUG_ON(xa, !xa_empty(xa));
/* And so does xa_insert */
/* But xa_insert does not */
xa_reserve(xa, 12345678, GFP_KERNEL);
XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) != 0);
xa_erase_index(xa, 12345678);
XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) !=
-EEXIST);
XA_BUG_ON(xa, xa_empty(xa));
XA_BUG_ON(xa, xa_erase(xa, 12345678) != NULL);
XA_BUG_ON(xa, !xa_empty(xa));
/* Can iterate through a reserved entry */

41
lib/xarray.c
View File

@ -1439,6 +1439,47 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
}
EXPORT_SYMBOL(__xa_cmpxchg);
/**
* __xa_insert() - Store this entry in the XArray if no entry is present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present. Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Any context. Expects xa_lock to be held on entry. May
* release and reacquire xa_lock if @gfp flags permit.
* Return: 0 if the store succeeded. -EEXIST if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
{
XA_STATE(xas, xa, index);
void *curr;
if (WARN_ON_ONCE(xa_is_advanced(entry)))
return -EINVAL;
if (!entry)
entry = XA_ZERO_ENTRY;
do {
curr = xas_load(&xas);
if (!curr) {
xas_store(&xas, entry);
if (xa_track_free(xa))
xas_clear_mark(&xas, XA_FREE_MARK);
} else {
xas_set_err(&xas, -EEXIST);
}
} while (__xas_nomem(&xas, gfp));
return xas_error(&xas);
}
EXPORT_SYMBOL(__xa_insert);
/**
* __xa_reserve() - Reserve this index in the XArray.
* @xa: XArray.