linux-toradex.git/include/linux/xarray.h, branch v5.1-rc1

XArray: Use xa_cmpxchg to implement xa_reserve

2019-02-20T22:08:54+00:00

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

2019-02-20T22:08:54+00:00

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: Mark xa_insert and xa_reserve as must_check

2019-02-09T05:00:49+00:00

If the user doesn't care about the return value from xa_insert(), then
they should be using xa_store() instead.  The point of xa_reserve() is
to get the return value early before taking another lock, so this should
also be __must_check.

Signed-off-by: Matthew Wilcox

XArray: Add cyclic allocation

2019-02-06T18:32:25+00:00

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

2019-02-06T18:32:23+00:00

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

2019-02-06T18:13:24+00:00

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

2019-02-06T18:12:15+00:00

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

2019-02-05T04:16:58+00:00

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: Fix an arithmetic error in xa_is_err

2019-01-17T12:19:42+00:00

There is a math problem here which leads to a lot of static checker
warnings for me:

net/sunrpc/clnt.c:451 rpc_new_client() error: (-4096) too low for ERR_PTR

Error values are from -1 to -4095 or from 0xffffffff to 0xfffff001 in
hexadecimal.  (I am assuming a 32 bit system for simplicity).  We are
using the lowest two bits to hold some internal XArray data so the
error is shifted two spaces to the left.  0xfffff001 << 2 is 0xffffc004.
And finally we want to check that BIT(1) is set so we add 2 which gives
us 0xffffc006.

In other words, we should be checking that "entry >= 0xffffc006", but
the check is actually testing if "entry >= 0xffffc002".

Fixes: 76b4e5299565 ("XArray: Permit storing 2-byte-aligned pointers")
Signed-off-by: Dan Carpenter 
[Use xa_mk_internal() instead of changing the bracketing]
Signed-off-by: Matthew Wilcox

XArray: Fix typo in comment

2019-01-14T17:52:16+00:00

Seems copy and paste typo, not a big deal but still
for consistency sake better to fix.

Signed-off-by: Cyrill Gorcunov 
Signed-off-by: Matthew Wilcox