ARC: Move header reallocation under db_mtx lock #15330
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As part of openzfs#14340 I've removed b_evict_lock, that played no role in ARC eviction process. But appears it played a secondary role of protecting b_hdr pointers in arc_buf_t during header reallocation by arc_hdr_realloc_crypt(), that, as found in openzfs#15293, may cause use after free races if some encrypted block is read while being synced after been writen. After closer look on b_evict_lock I still do not believe it covered all the possible races, so I am not eager to resurrect it. Instead this refactors arc_hdr_realloc_crypt() into arc_realloc_crypt() and moves its calls from arc_write_ready() into upper levels ready callbacks, like dbuf_write_ready(), where it is protected by existing db_mtx, protecting also all the arc buffer accesses. Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored by: iXsystems, Inc.
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Assuming you're expecting this to help with #11679, I got this after a few runs of If I misunderstood your expectations for this patch, my apologies for the noise. e: And on my x86_64 system, it dies with: |
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As part of #14340 I've removed b_evict_lock, that played no role in ARC eviction process. But appears it played a secondary role of protecting b_hdr pointers in arc_buf_t during header reallocation by arc_hdr_realloc_crypt(), that, as found in #15293, may cause use after free races if some encrypted block is read while being synced after been writen.
After closer look on b_evict_lock I still do not believe it covered all the possible races, so I am not eager to resurrect it. Instead this refactors arc_hdr_realloc_crypt() into arc_realloc_crypt() and moves its calls from arc_write_ready() into upper levels ready callbacks, like dbuf_write_ready(), where it is protected by existing db_mtx, protecting also all the arc buffer accesses.
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Signed-off-by.