linux/lib/xarray.c, branch v5.1

XArray: Fix xa_reserve for 2-byte aligned entries

2019-02-21T22:54:44Z

If we reserve index 0, the next entry to be stored there might be 2-byte aligned. That means we have to create the root xa_node at the time of reserving the initial entry. Signed-off-by: Matthew Wilcox

XArray: Fix xa_erase of 2-byte aligned entries

2019-02-21T22:36:45Z

xas_store() was interpreting the entry it found in the array as a node entry if the bottom two bits had value 2. That's only true if either the entry is in the root node or in a non-leaf node. Signed-off-by: Matthew Wilcox

XArray: Use xa_cmpxchg to implement xa_reserve

2019-02-20T22:08:54Z

Jason feels this is clearer, and it saves a function and an exported symbol. Suggested-by: Jason Gunthorpe Signed-off-by: Matthew Wilcox

XArray: Fix xa_release in allocating arrays

2019-02-20T22:08:54Z

xa_cmpxchg() was a little too magic in turning ZERO entries into NULL, and would leave the entry set to the ZERO entry instead of releasing it for future use. After careful review of existing users of xa_cmpxchg(), change the semantics so that it does not translate either incoming argument from NULL into ZERO entries. Add several tests to the test-suite to make sure this problem doesn't come back. Reported-by: Jason Gunthorpe Signed-off-by: Matthew Wilcox

XArray: Add cyclic allocation

2019-02-06T18:32:25Z

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

XArray: Redesign xa_alloc API

2019-02-06T18:32:23Z

It was too easy to forget to initialise the start index. Add an xa_limit data structure which can be used to pass min & max, and define a couple of special values for common cases. Also add some more tests cribbed from the IDR test suite. Change the return value from -ENOSPC to -EBUSY to match xa_insert(). Signed-off-by: Matthew Wilcox

XArray: Add support for 1s-based allocation

2019-02-06T18:13:24Z

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

XArray: Change xa_insert to return -EBUSY

2019-02-06T18:12:15Z

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

XArray: Update xa_erase family descriptions

2019-02-05T04:16:58Z

xa_erase does not allocate memory and doesn't have a gfp parameter. Update the descriptions of all four variants to be more useful. Signed-off-by: Matthew Wilcox

XArray: Honour reserved entries in xa_insert

2019-01-07T03:12:58Z

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