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XArray: Unify xa_cmpxchg and __xa_cmpxchg
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xa_cmpxchg() was one of the largest functions in the xarray
implementation.  By turning it into a wrapper and having the callers
take the lock (like several other functions), we save 160 bytes on a
tinyconfig build and reduce the duplication in xarray.c.

Signed-off-by: Matthew Wilcox <[email protected]>
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Matthew Wilcox committed Nov 5, 2018
1 parent 4c0608f commit c5beb07
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Showing 2 changed files with 69 additions and 85 deletions.
113 changes: 69 additions & 44 deletions include/linux/xarray.h
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Original file line number Diff line number Diff line change
Expand Up @@ -289,8 +289,6 @@ struct xarray {
void xa_init_flags(struct xarray *, gfp_t flags);
void *xa_load(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);
void *xa_store_range(struct xarray *, unsigned long first, unsigned long last,
void *entry, gfp_t);
bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t);
Expand Down Expand Up @@ -359,48 +357,6 @@ static inline void *xa_erase(struct xarray *xa, unsigned long index)
return xa_store(xa, index, NULL, 0);
}

/**
* 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: Process 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;
}

/**
* xa_release() - Release a reserved entry.
* @xa: XArray.
* @index: Index of entry.
*
* After calling xa_reserve(), you can call this function to release the
* reservation. If the entry at @index has been stored to, this function
* will do nothing.
*/
static inline void xa_release(struct xarray *xa, unsigned long index)
{
xa_cmpxchg(xa, index, NULL, NULL, 0);
}

/**
* xa_for_each() - Iterate over a portion of an XArray.
* @xa: XArray.
Expand Down Expand Up @@ -534,6 +490,61 @@ static inline void *xa_erase_irq(struct xarray *xa, unsigned long index)
return entry;
}

/**
* xa_cmpxchg() - 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.
*
* If the entry at @index is the same as @old, replace it with @entry.
* If the return value is equal to @old, then the exchange was successful.
*
* Context: Any context. Takes and releases the xa_lock. 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(struct xarray *xa, unsigned long index,
void *old, void *entry, gfp_t gfp)
{
void *curr;

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

return curr;
}

/**
* 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: Process 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;
}

/**
* xa_alloc() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
Expand Down Expand Up @@ -699,6 +710,20 @@ int xa_reserve_irq(struct xarray *xa, unsigned long index, gfp_t gfp)
return ret;
}

/**
* xa_release() - Release a reserved entry.
* @xa: XArray.
* @index: Index of entry.
*
* After calling xa_reserve(), you can call this function to release the
* reservation. If the entry at @index has been stored to, this function
* will do nothing.
*/
static inline void xa_release(struct xarray *xa, unsigned long index)
{
xa_cmpxchg(xa, index, NULL, NULL, 0);
}

/* Everything below here is the Advanced API. Proceed with caution. */

/*
Expand Down
41 changes: 0 additions & 41 deletions lib/xarray.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1406,47 +1406,6 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
}
EXPORT_SYMBOL(__xa_store);

/**
* xa_cmpxchg() - 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.
*
* If the entry at @index is the same as @old, replace it with @entry.
* If the return value is equal to @old, then the exchange was successful.
*
* Context: Process context. Takes and releases the xa_lock. May sleep
* if the @gfp flags permit.
* Return: The old value at this index or xa_err() if an error happened.
*/
void *xa_cmpxchg(struct xarray *xa, unsigned long index,
void *old, void *entry, gfp_t gfp)
{
XA_STATE(xas, xa, index);
void *curr;

if (WARN_ON_ONCE(xa_is_internal(entry)))
return XA_ERROR(-EINVAL);

do {
xas_lock(&xas);
curr = xas_load(&xas);
if (curr == XA_ZERO_ENTRY)
curr = NULL;
if (curr == old) {
xas_store(&xas, entry);
if (xa_track_free(xa) && entry)
xas_clear_mark(&xas, XA_FREE_MARK);
}
xas_unlock(&xas);
} while (xas_nomem(&xas, gfp));

return xas_result(&xas, curr);
}
EXPORT_SYMBOL(xa_cmpxchg);

/**
* __xa_cmpxchg() - Store this entry in the XArray.
* @xa: XArray.
Expand Down

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