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2021-03-30XArray: Fix splitting to non-zero ordersMatthew Wilcox (Oracle)1-2/+2
Splitting an order-4 entry into order-2 entries would leave the array containing pointers to 000040008000c000 instead of 000044448888cccc. This is a one-character fix, but enhance the test suite to check this case. Reported-by: Zi Yan <ziy@nvidia.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2021-03-30XArray: Fix split documentationMatthew Wilcox (Oracle)1-3/+4
I wrote the documentation backwards; the new order of the entry is stored in the xas and the caller passes the old entry. Reported-by: Zi Yan <ziy@nvidia.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-10-20Merge tag 'xarray-5.9' of git://git.infradead.org/users/willy/xarrayLinus Torvalds1-1/+24
Pull XArray updates from Matthew Wilcox: - Fix the test suite after introduction of the local_lock - Fix a bug in the IDA spotted by Coverity - Change the API that allows the workingset code to delete a node - Fix xas_reload() when dealing with entries that occupy multiple indices - Add a few more tests to the test suite - Fix an unsigned int being shifted into an unsigned long * tag 'xarray-5.9' of git://git.infradead.org/users/willy/xarray: XArray: Fix xas_create_range for ranges above 4 billion radix-tree: fix the comment of radix_tree_next_slot() XArray: Fix xas_reload for multi-index entries XArray: Add private interface for workingset node deletion XArray: Fix xas_for_each_conflict documentation XArray: Test marked multiorder iterations XArray: Test two more things about xa_cmpxchg ida: Free allocated bitmap in error path radix tree test suite: Fix compilation
2020-10-16XArray: add xas_splitMatthew Wilcox (Oracle)1-9/+159
In order to use multi-index entries for huge pages in the page cache, we need to be able to split a multi-index entry (eg if a file is truncated in the middle of a huge page entry). This version does not support splitting more than one level of the tree at a time. This is an acceptable limitation for the page cache as we do not expect to support order-12 pages in the near future. [akpm@linux-foundation.org: export xas_split_alloc() to modules] [willy@infradead.org: fix xarray split] Link: https://lkml.kernel.org/r/20200910175450.GV6583@casper.infradead.org [willy@infradead.org: fix xarray] Link: https://lkml.kernel.org/r/20201001233943.GW20115@casper.infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Qian Cai <cai@lca.pw> Cc: Song Liu <songliubraving@fb.com> Link: https://lkml.kernel.org/r/20200903183029.14930-3-willy@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-16XArray: add xa_get_orderMatthew Wilcox (Oracle)1-0/+40
Patch series "Fix read-only THP for non-tmpfs filesystems". As described more verbosely in the [3/3] changelog, we can inadvertently put an order-0 page in the page cache which occupies 512 consecutive entries. Users are running into this if they enable the READ_ONLY_THP_FOR_FS config option; see https://bugzilla.kernel.org/show_bug.cgi?id=206569 and Qian Cai has also reported it here: https://lore.kernel.org/lkml/20200616013309.GB815@lca.pw/ This is a rather intrusive way of fixing the problem, but has the advantage that I've actually been testing it with the THP patches, which means that it sees far more use than it does upstream -- indeed, Song has been entirely unable to reproduce it. It also has the advantage that it removes a few patches from my gargantuan backlog of THP patches. This patch (of 3): This function returns the order of the entry at the index. We need this because there isn't space in the shadow entry to encode its order. [akpm@linux-foundation.org: export xa_get_order to modules] Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Qian Cai <cai@lca.pw> Cc: Song Liu <songliubraving@fb.com> Link: https://lkml.kernel.org/r/20200903183029.14930-1-willy@infradead.org Link: https://lkml.kernel.org/r/20200903183029.14930-2-willy@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13XArray: Fix xas_create_range for ranges above 4 billionMatthew Wilcox (Oracle)1-1/+1
The 'sibs' variable would be shifted as a 32-bit integer, so if 'shift' is more than 32, this is undefined behaviour. In practice, this doesn't happen because the page cache is the only user and nobody uses 16TB pages. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-10-13XArray: Add private interface for workingset node deletionMatthew Wilcox (Oracle)1-0/+23
Move the tricky bits of dealing with the XArray from the workingset code to the XArray. Make it clear in the documentation that this is a private interface, and only export it for the benefit of the test suite. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-03-12xarray: Fix early termination of xas_for_each_markedMatthew Wilcox (Oracle)1-0/+2
xas_for_each_marked() is using entry == NULL as a termination condition of the iteration. When xas_for_each_marked() is used protected only by RCU, this can however race with xas_store(xas, NULL) in the following way: TASK1 TASK2 page_cache_delete() find_get_pages_range_tag() xas_for_each_marked() xas_find_marked() off = xas_find_chunk() xas_store(&xas, NULL) xas_init_marks(&xas); ... rcu_assign_pointer(*slot, NULL); entry = xa_entry(off); And thus xas_for_each_marked() terminates prematurely possibly leading to missed entries in the iteration (translating to missing writeback of some pages or a similar problem). If we find a NULL entry that has been marked, skip it (unless we're trying to allocate an entry). Reported-by: Jan Kara <jack@suse.cz> CC: stable@vger.kernel.org Fixes: ef8e5717db01 ("page cache: Convert delete_batch to XArray") Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-02-27XArray: Optimise xas_sibling() if !CONFIG_XARRAY_MULTIMatthew Wilcox (Oracle)1-1/+1
If CONFIG_XARRAY_MULTI is disabled, then xas_sibling() must be false. Reported-by: JaeJoon Jung <rgbi3307@gmail.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2020-01-31XArray: Fix xas_pause for large multi-index entriesMatthew Wilcox (Oracle)1-1/+1
Inspired by the recent Coverity report, I looked for other places where the offset wasn't being converted to an unsigned long before being shifted, and I found one in xas_pause() when the entry being paused is of order >32. Fixes: b803b42823d0 ("xarray: Add XArray iterators") Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: stable@vger.kernel.org
2020-01-31XArray: Fix xa_find_next for large multi-index entriesMatthew Wilcox (Oracle)1-1/+2
Coverity pointed out that xas_sibling() was shifting xa_offset without promoting it to an unsigned long first, so the shift could cause an overflow and we'd get the wrong answer. The fix is obvious, and the new test-case provokes UBSAN to report an error: runtime error: shift exponent 60 is too large for 32-bit type 'int' Fixes: 19c30f4dd092 ("XArray: Fix xa_find_after with multi-index entries") Reported-by: Bjorn Helgaas <bhelgaas@google.com> Reported-by: Kees Cook <keescook@chromium.org> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: stable@vger.kernel.org
2020-01-17XArray: Fix xas_find returning too many entriesMatthew Wilcox (Oracle)1-2/+8
If you call xas_find() with the initial index > max, it should have returned NULL but was returning the entry at index. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: stable@vger.kernel.org
2020-01-17XArray: Fix xa_find_after with multi-index entriesMatthew Wilcox (Oracle)1-7/+13
If the entry is of an order which is a multiple of XA_CHUNK_SIZE, the current detection of sibling entries does not work. Factor out an xas_sibling() function to make xa_find_after() a little more understandable, and write a new implementation that doesn't suffer from the same bug. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: stable@vger.kernel.org
2020-01-17XArray: Fix infinite loop with entry at ULONG_MAXMatthew Wilcox (Oracle)1-0/+3
If there is an entry at ULONG_MAX, xa_for_each() will overflow the 'index + 1' in xa_find_after() and wrap around to 0. Catch this case and terminate the loop by returning NULL. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: stable@vger.kernel.org
2019-11-08XArray: Fix xas_pause at ULONG_MAXMatthew Wilcox (Oracle)1-3/+5
If we were unlucky enough to call xas_pause() when the index was at ULONG_MAX (or a multi-slot entry which ends at ULONG_MAX), we would wrap the index back around to 0 and restart the iteration from the beginning. Use the XAS_BOUNDS state to indicate that we should just stop the iteration. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2019-07-01XArray: Fix xas_next() with a single entry at 0Matthew Wilcox (Oracle)1-0/+4
If there is only a single entry at 0, the first time we call xas_next(), we return the entry. Unfortunately, all subsequent times we call xas_next(), we also return the entry at 0 instead of noticing that the xa_index is now greater than zero. This broke find_get_pages_contig(). Fixes: 64d3e9a9e0cc ("xarray: Step through an XArray") Reported-by: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2019-05-31mm: fix page cache convergence regressionJohannes Weiner1-2/+10
Since a28334862993 ("page cache: Finish XArray conversion"), on most major Linux distributions, the page cache doesn't correctly transition when the hot data set is changing, and leaves the new pages thrashing indefinitely instead of kicking out the cold ones. On a freshly booted, freshly ssh'd into virtual machine with 1G RAM running stock Arch Linux: [root@ham ~]# ./reclaimtest.sh + dd of=workingset-a bs=1M count=0 seek=600 + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + ./mincore workingset-a 153600/153600 workingset-a + dd of=workingset-b bs=1M count=0 seek=600 + cat workingset-b + cat workingset-b + cat workingset-b + cat workingset-b + ./mincore workingset-a workingset-b 104029/153600 workingset-a 120086/153600 workingset-b + cat workingset-b + cat workingset-b + cat workingset-b + cat workingset-b + ./mincore workingset-a workingset-b 104029/153600 workingset-a 120268/153600 workingset-b workingset-b is a 600M file on a 1G host that is otherwise entirely idle. No matter how often it's being accessed, it won't get cached. While investigating, I noticed that the non-resident information gets aggressively reclaimed - /proc/vmstat::workingset_nodereclaim. This is a problem because a workingset transition like this relies on the non-resident information tracked in the page cache tree of evicted file ranges: when the cache faults are refaults of recently evicted cache, we challenge the existing active set, and that allows a new workingset to establish itself. Tracing the shrinker that maintains this memory revealed that all page cache tree nodes were allocated to the root cgroup. This is a problem, because 1) the shrinker sizes the amount of non-resident information it keeps to the size of the cgroup's other memory and 2) on most major Linux distributions, only kernel threads live in the root cgroup and everything else gets put into services or session groups: [root@ham ~]# cat /proc/self/cgroup 0::/user.slice/user-0.slice/session-c1.scope As a result, we basically maintain no non-resident information for the workloads running on the system, thus breaking the caching algorithm. Looking through the code, I found the culprit in the above-mentioned patch: when switching from the radix tree to xarray, it dropped the __GFP_ACCOUNT flag from the tree node allocations - the flag that makes sure the allocated memory gets charged to and tracked by the cgroup of the calling process - in this case, the one doing the fault. To fix this, allow xarray users to specify per-tree flag that makes xarray allocate nodes using __GFP_ACCOUNT. Then restore the page cache tree annotation to request such cgroup tracking for the cache nodes. With this patch applied, the page cache correctly converges on new workingsets again after just a few iterations: [root@ham ~]# ./reclaimtest.sh + dd of=workingset-a bs=1M count=0 seek=600 + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + cat workingset-a + ./mincore workingset-a 153600/153600 workingset-a + dd of=workingset-b bs=1M count=0 seek=600 + cat workingset-b + ./mincore workingset-a workingset-b 124607/153600 workingset-a 87876/153600 workingset-b + cat workingset-b + ./mincore workingset-a workingset-b 81313/153600 workingset-a 133321/153600 workingset-b + cat workingset-b + ./mincore workingset-a workingset-b 63036/153600 workingset-a 153600/153600 workingset-b Cc: stable@vger.kernel.org # 4.20+ Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2019-02-21XArray: Fix xa_reserve for 2-byte aligned entriesMatthew Wilcox1-3/+5
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 <willy@infradead.org>
2019-02-21XArray: Fix xa_erase of 2-byte aligned entriesMatthew Wilcox1-1/+1
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 <willy@infradead.org>
2019-02-20XArray: Use xa_cmpxchg to implement xa_reserveMatthew Wilcox1-36/+0
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>
2019-02-20XArray: Fix xa_release in allocating arraysMatthew Wilcox1-5/+1
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 <jgg@ziepe.ca> Signed-off-by: Matthew Wilcox <willy@infradead.org>
2019-02-06XArray: Add cyclic allocationMatthew Wilcox1-0/+50
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>
2019-02-06XArray: Redesign xa_alloc APIMatthew Wilcox1-15/+14
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 <willy@infradead.org>
2019-02-06XArray: Add support for 1s-based allocationMatthew Wilcox1-0/+11
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>
2019-02-06XArray: Change xa_insert to return -EBUSYMatthew Wilcox1-2/+2
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>
2019-02-04XArray: Update xa_erase family descriptionsMatthew Wilcox1-9/+8
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 <willy@infradead.org>
2019-01-06XArray: Honour reserved entries in xa_insertMatthew Wilcox1-0/+41
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>
2019-01-06XArray: Permit storing 2-byte-aligned pointersMatthew Wilcox1-9/+13
On m68k, statically allocated pointers may only be two-byte aligned. This clashes with the XArray's method for tagging internal pointers. Permit storing these pointers in single slots (ie not in multislots). Signed-off-by: Matthew Wilcox <willy@infradead.org>
2019-01-06XArray: Turn xa_init_flags into a static inlineMatthew Wilcox1-29/+0
A regular xa_init_flags() put all dynamically-initialised XArrays into the same locking class. That leads to lockdep believing that taking one XArray lock while holding another is a deadlock. It's possible to work around some of these situations with separate locking classes for irq/bh/regular XArrays, and SINGLE_DEPTH_NESTING, but that's ugly, and it doesn't work for all situations (where we have completely unrelated XArrays). Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-12-13XArray: Fix xa_alloc when id exceeds maxMatthew Wilcox1-5/+3
Specifying a starting ID greater than the maximum ID isn't something attempted very often, but it should fail. It was succeeding due to xas_find_marked() returning the wrong error state, so add tests for both xa_alloc() and xas_find_marked(). Fixes: b803b42823d0 ("xarray: Add XArray iterators") Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-16XArray: Correct xa_store_rangeMatthew Wilcox1-2/+3
The explicit '64' should have been BITS_PER_LONG, but while looking at this code I realised I meant to use __ffs(), not ilog2(). Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05XArray: Fix DocumentationMatthew Wilcox1-5/+5
Minor fixes. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05XArray: Handle NULL pointers differently for allocationMatthew Wilcox1-3/+10
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>
2018-11-05XArray: Unify xa_store and __xa_storeMatthew Wilcox1-33/+25
Saves around 115 bytes on a tinyconfig build and reduces the amount of code duplication in the XArray implementation. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05XArray: Turn xa_erase into an exported functionMatthew Wilcox1-0/+24
Make xa_erase() take the spinlock and then call __xa_erase(), but make it out of line since it's such a common function. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05XArray: Unify xa_cmpxchg and __xa_cmpxchgMatthew Wilcox1-41/+0
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 <willy@infradead.org>
2018-11-05XArray: Regularise xa_reserveMatthew Wilcox1-11/+7
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>
2018-11-05XArray: Export __xa_foo to non-GPL modulesMatthew Wilcox1-3/+3
Without this, it's not possible to use static inlines like xa_store_bh() and xa_erase_irq(). Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-11-05XArray: Fix xa_for_each with a single element at 0Matthew Wilcox1-0/+2
The following sequence of calls would result in an infinite loop in xa_find_after(): xa_store(xa, 0, x, GFP_KERNEL); index = 0; xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) { } xa_find_after() was confusing the situation where we found no entry in the tree with finding a multiorder entry, so it would look for the successor entry forever. Just check for this case explicitly. Includes a few new checks in the test suite to be sure this doesn't reappear. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Add range store functionalityMatthew Wilcox1-2/+95
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>
2018-10-21xarray: Track free entries in an XArrayMatthew Wilcox1-4/+84
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>
2018-10-21xarray: Add xa_reserve and xa_releaseMatthew Wilcox1-0/+47
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>
2018-10-21xarray: Add xas_create_rangeMatthew Wilcox1-0/+50
This hopefully temporary function is useful for users who have not yet been converted to multi-index entries. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Add xas_for_each_conflictMatthew Wilcox1-0/+61
This iterator iterates over each entry that is stored in the index or indices specified by the xa_state. This is intended for use for a conditional store of a multiindex entry, or to allow entries which are about to be removed from the xarray to be disposed of properly. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Step through an XArrayMatthew Wilcox1-0/+74
The xas_next and xas_prev functions move the xas index by one position, and adjust the rest of the iterator state to match it. This is more efficient than calling xas_set() as it keeps the iterator at the leaves of the tree instead of walking the iterator from the root each time. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Destroy an XArrayMatthew Wilcox1-0/+28
This function frees all the internal memory allocated to the xarray and reinitialises it to be empty. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Extract entries from an XArrayMatthew Wilcox1-0/+80
The xa_extract function combines the functionality of radix_tree_gang_lookup() and radix_tree_gang_lookup_tagged(). It extracts entries matching the specified filter into a normal array. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Add XArray iteratorsMatthew Wilcox1-0/+292
The xa_for_each iterator allows the user to efficiently walk a range of the array, executing the loop body once for each entry in that range that matches the filter. This commit also includes xa_find() and xa_find_after() which are helper functions for xa_for_each() but may also be useful in their own right. In the xas family of functions, we have xas_for_each(), xas_find(), xas_next_entry(), xas_for_each_tagged(), xas_find_tagged(), xas_next_tagged() and xas_pause(). Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Add XArray conditional store operationsMatthew Wilcox1-0/+71
Like cmpxchg(), xa_cmpxchg will only store to the index if the current entry matches the old entry. It returns the current entry, which is usually more useful than the errno returned by radix_tree_insert(). For the users who really only want the errno, the xa_insert() wrapper provides a more convenient calling convention. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-10-21xarray: Add XArray unconditional store operationsMatthew Wilcox1-0/+693
xa_store() differs from radix_tree_insert() in that it will overwrite an existing element in the array rather than returning an error. This is the behaviour which most users want, and those that want more complex behaviour generally want to use the xas family of routines anyway. For memory allocation, xa_store() will first attempt to request memory from the slab allocator; if memory is not immediately available, it will drop the xa_lock and allocate memory, keeping a pointer in the xa_state. It does not use the per-CPU cache, although those will continue to exist until all radix tree users are converted to the xarray. This patch also includes xa_erase() and __xa_erase() for a streamlined way to store NULL. Since there is no need to allocate memory in order to store a NULL in the XArray, we do not need to trouble the user with deciding what memory allocation flags to use. Signed-off-by: Matthew Wilcox <willy@infradead.org>
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