user/sven/linux.git/lib/maple_tree.c, branch v6.5.3

maple_tree: disable mas_wr_append() when other readers are possible

2023-08-24T21:59:47Z

The current implementation of append may cause duplicate data and/or incorrect ranges to be returned to a reader during an update. Although this has not been reported or seen, disable the append write operation while the tree is in rcu mode out of an abundance of caution. During the analysis of the mas_next_slot() the following was artificially created by separating the writer and reader code: Writer: reader: mas_wr_append set end pivot updates end metata Detects write to last slot last slot write is to start of slot store current contents in slot overwrite old end pivot mas_next_slot(): read end metadata read old end pivot return with incorrect range store new value Alternatively: Writer: reader: mas_wr_append set end pivot updates end metata Detects write to last slot last lost write to end of slot store value mas_next_slot(): read end metadata read old end pivot read new end pivot return with incorrect range set old end pivot There may be other accesses that are not safe since we are now updating both metadata and pointers, so disabling append if there could be rcu readers is the safest action. Link: https://lkml.kernel.org/r/20230819004356.1454718-2-Liam.Howlett@oracle.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett Cc: Signed-off-by: Andrew Morton

maple_tree: set the node limit when creating a new root node

2023-07-17T19:53:22Z

Set the node limit of the root node so that the last pivot of all nodes is the node limit (if the node is not full). This patch also fixes a bug in mas_rev_awalk(). Effectively, always setting a maximum makes mas_logical_pivot() behave as mas_safe_pivot(). Without this fix, it is possible that very small tasks would fail to find the correct gap. Although this has not been observed with real tasks, it has been reported to happen in m68k nommu running the maple tree tests. Link: https://lkml.kernel.org/r/20230711035444.526-1-zhangpeng.00@bytedance.com Link: https://lore.kernel.org/linux-mm/CAMuHMdV4T53fOw7VPoBgPR7fP6RYqf=CBhD_y_vOg53zZX_DnA@mail.gmail.com/ Link: https://lkml.kernel.org/r/20230711035444.526-2-zhangpeng.00@bytedance.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Tested-by: Geert Uytterhoeven Cc: Signed-off-by: Andrew Morton

maple_tree: simplify and clean up mas_wr_node_store()

2023-06-09T23:25:45Z

Simplify and clean up mas_wr_node_store(), remove unnecessary code. Link: https://lkml.kernel.org/r/20230524031247.65949-10-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton

maple_tree: rework mas_wr_slot_store() to be cleaner and more efficient.

2023-06-09T23:25:45Z

Get whether the two gaps to be overwritten are empty to avoid calling mas_update_gap() all the time. Also clean up the code and add comments. Link: https://lkml.kernel.org/r/20230524031247.65949-9-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton

maple_tree: add comments and some minor cleanups to mas_wr_append()

2023-06-09T23:25:45Z

Add comment for mas_wr_append(), move mas_update_gap() into mas_wr_append(), and other cleanups to make mas_wr_modify() cleaner. Link: https://lkml.kernel.org/r/20230524031247.65949-8-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton

maple_tree: add mas_wr_new_end() to calculate new_end accurately

2023-06-09T23:25:45Z

The previous new_end calculation is inaccurate, because it assumes that two new pivots must be added (this is inaccurate), and sometimes it will miss the fast path and enter the slow path. Add mas_wr_new_end() to accurately calculate new_end to make the conditions for entering the fast path more accurate. Link: https://lkml.kernel.org/r/20230524031247.65949-7-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton

maple_tree: make the code symmetrical in mas_wr_extend_null()

2023-06-09T23:25:44Z

Just make the code symmetrical to improve readability. Link: https://lkml.kernel.org/r/20230524031247.65949-6-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton

maple_tree: simplify mas_is_span_wr()

2023-06-09T23:25:44Z

Make the code for detecting spanning writes more concise. Link: https://lkml.kernel.org/r/20230524031247.65949-5-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton

maple_tree: fix the arguments to __must_hold()

2023-06-09T23:25:44Z

Fix the arguments to __must_hold() to make sparse work. Link: https://lkml.kernel.org/r/20230524031247.65949-4-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton

maple_tree: drop mas_{rev_}alloc() and mas_fill_gap()

2023-06-09T23:25:44Z

mas_{rev_}alloc() and mas_fill_gap() are no longer used, delete them. Link: https://lkml.kernel.org/r/20230524031247.65949-3-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang Reviewed-by: Liam R. Howlett Signed-off-by: Andrew Morton