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authorSong Liu <songliubraving@fb.com>2019-10-18 20:20:40 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-10-19 06:32:33 -0400
commitaa5de305c90c995321df452f274fe75b52bd8fcc (patch)
tree6ce098dda02fa906d14be6e8bd338d34a105945d /scripts/gdb
parentef18a1ca847b01cb7296f11a728cb2f5ef671760 (diff)
kernel/events/uprobes.c: only do FOLL_SPLIT_PMD for uprobe register
Attaching uprobe to text section in THP splits the PMD mapped page table into PTE mapped entries. On uprobe detach, we would like to regroup PMD mapped page table entry to regain performance benefit of THP. However, the regroup is broken For perf_event based trace_uprobe. This is because perf_event based trace_uprobe calls uprobe_unregister twice on close: first in TRACE_REG_PERF_CLOSE, then in TRACE_REG_PERF_UNREGISTER. The second call will split the PMD mapped page table entry, which is not the desired behavior. Fix this by only use FOLL_SPLIT_PMD for uprobe register case. Add a WARN() to confirm uprobe unregister never work on huge pages, and abort the operation when this WARN() triggers. Link: http://lkml.kernel.org/r/20191017164223.2762148-6-songliubraving@fb.com Fixes: 5a52c9df62b4 ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT") Signed-off-by: Song Liu <songliubraving@fb.com> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: William Kucharski <william.kucharski@oracle.com> Cc: Yang Shi <yang.shi@linux.alibaba.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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