Commit Graph

14 Commits

Author SHA1 Message Date
Matthew Wilcox
962033d55d XArray: Use xa_cmpxchg to implement xa_reserve
Jason feels this is clearer, and it saves a function and an exported
symbol.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
2019-02-20 17:08:54 -05:00
Matthew Wilcox
2fa044e51a XArray: Add cyclic allocation
This differs slightly from the IDR equivalent in five ways.

1. It can allocate up to UINT_MAX instead of being limited to INT_MAX,
   like xa_alloc().  Also like xa_alloc(), it will write to the 'id'
   pointer before placing the entry in the XArray.
2. The 'next' cursor is allocated separately from the XArray instead
   of being part of the IDR.  This saves memory for all the users which
   do not use the cyclic allocation API and suits some users better.
3. It returns -EBUSY instead of -ENOSPC.
4. It will attempt to wrap back to the minimum value on memory allocation
   failure as well as on an -EBUSY error, assuming that a user would
   rather allocate a small ID than suffer an ID allocation failure.
5. It reports whether it has wrapped, which is important to some users.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2019-02-06 13:32:25 -05:00
Matthew Wilcox
3ccaf57a6a XArray: Add support for 1s-based allocation
A lot of places want to allocate IDs starting at 1 instead of 0.
While the xa_alloc() API supports this, it's not very efficient if lots
of IDs are allocated, due to having to walk down to the bottom of the
tree to see if ID 1 is available, then all the way over to the next
non-allocated ID.  This method marks ID 0 as being occupied which wastes
one slot in the XArray, but preserves xa_empty() as working.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2019-02-06 13:13:24 -05:00
Matthew Wilcox
fd9dc93e36 XArray: Change xa_insert to return -EBUSY
Userspace translates EEXIST to "File exists" which isn't a very good
error message for the problem.  "Device or resource busy" is a better
indication of what went wrong.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2019-02-06 13:12:15 -05:00
Matthew Wilcox
b0606fed6e XArray: Honour reserved entries in xa_insert
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>
2019-01-06 22:12:58 -05:00
Matthew Wilcox
55f3f7eab7 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: Matthew Wilcox <willy@infradead.org>
2018-12-06 08:26:17 -05:00
Matthew Wilcox
804dfaf01b XArray: Fix Documentation
Minor fixes.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05 16:38:10 -05:00
Matthew Wilcox
d9c480435a XArray: Handle NULL pointers differently for allocation
For allocating XArrays, it makes sense to distinguish beteen erasing an
entry and storing NULL.  Storing NULL keeps the index allocated with a
NULL pointer associated with it while xa_erase() frees the index.  Some
existing IDR users rely on this ability.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05 16:38:09 -05:00
Matthew Wilcox
84e5acb76d XArray: Add xa_store_bh() and xa_store_irq()
These convenience wrappers disable interrupts while taking the spinlock.
A number of drivers would otherwise have to open-code these functions.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05 16:38:09 -05:00
Matthew Wilcox
4c0608f4a0 XArray: Regularise xa_reserve
The xa_reserve() function was a little unusual in that it attempted to
be callable for all kinds of locking scenarios.  Make it look like the
other APIs with __xa_reserve, xa_reserve_bh and xa_reserve_irq variants.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05 16:38:08 -05:00
Matthew Wilcox
0e9446c35a xarray: Add range store functionality
This version of xa_store_range() really only supports load and store.
Our only user only needs basic load and store functionality, so there's
no need to do the extra work to support marking and overlapping stores
correctly yet.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21 10:46:46 -04:00
Matthew Wilcox
371c752dc6 xarray: Track free entries in an XArray
Add the optional ability to track which entries in an XArray are free
and provide xa_alloc() to replace most of the functionality of the IDR.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21 10:46:32 -04:00
Matthew Wilcox
9f14d4f1f1 xarray: Add xa_reserve and xa_release
This function reserves a slot in the XArray for users which need
to acquire multiple locks before storing their entry in the tree and
so cannot use a plain xa_store().

Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21 10:46:00 -04:00
Matthew Wilcox
992a8e60e3 xarray: Add documentation
This is documentation on how to use the XArray, not details about its
internal implementation.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Josef Bacik <jbacik@fb.com>
2018-10-21 10:45:57 -04:00