the oops under heavy load

[tom wang <wddi_1976@xxxxxxxxxxxx>]

hi:
 xfs developers.

 when I test xfs under heavy load, I found an oops at
 the function unlock_page(). After study the trace of
oops,
 I found that the oops happened here.
 (fs/xfs/pagebuf/page_buf.c 562 )


 if (!pb->pb_locked) {
       for (pi = 0; pi < page_count; pi++) {
            unlock_page(pb->pb_pages[pi]);
       }
 }

 I investigate the src code. I found that when the
memory is tight,
 the function (_pagebuf_lookup_pages) did not return
and it also did not check
 the pointer pb->pb_pages[pi], so if the memory is
tight, pb->pb_pages[pi]
 maybe NULL, at that time, if we called
unlock_page(pb->pb_pages[pi]), oops
 will happen.


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