Messages in this thread Patch in this message |  | | Date | Thu, 26 Apr 2001 04:58:00 +0200 | From | Andrea Arcangeli <> | Subject | RAWIO-6 update [was Re: RAWIO-5 and O_DIRECT-3 updates] |
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On Tue, Apr 24, 2001 at 08:56:00AM +0200, Andrea Arcangeli wrote: > I fixed a new bug pointed out by Andrew and discussed on the kiobuf list > (thanks Andrew!) (lock_kiovec was not handling correctly a failed trylockpage > and could unlock pages locked by other people, not a big deal though as such > function is never called in the whole pre6 and I'm wondering if it make sense > at all to allow the pinned pages to be locked down in 2.4 [it certainly is > still necessary in 2.2 for all the reads from disk]). However I didn't killed > that function just in case there's an useful use of it. New updated rawio patch > against vanilla 2.4.4pre6 is here: > > ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/patches/v2.4/2.4.4pre6/rawio-5.bz2
My 2.4 rawio-* patches had from the start an annoying bug that can be triggered only with machines with more than 1G (I know, strictly speaking some houndred MB less than 1G for vmalloc and friends but you got it)
The bug is caused by this debugging check in the highmem bounce buffer code that I didn't trapped while keeping the slab cache constructed to improve the allocation of the buffer headers:
memset(&bh->b_wait, -1, sizeof(bh->b_wait));
The side effect of the bug is that the kernel locks hard while paging init in during boot (as said above only if you have more than 1G of ram). You can guess why I didn't trapped it during regression testing. So this is the incremental fix against rawio-5:
diff -urN rawio-5/mm/highmem.c rawio-6/mm/highmem.c --- rawio-5/mm/highmem.c Thu Dec 14 22:34:14 2000 +++ rawio-6/mm/highmem.c Thu Apr 26 02:37:07 2001 @@ -207,6 +207,10 @@ bh_orig->b_end_io(bh_orig, uptodate); __free_page(bh->b_page); +#ifdef HIGHMEM_DEBUG + /* Don't clobber the constructed slab cache */ + init_waitqueue_head(&bh->b_wait); +#endif kmem_cache_free(bh_cachep, bh); } @@ -260,12 +264,14 @@ bh->b_count = bh_orig->b_count; bh->b_rdev = bh_orig->b_rdev; bh->b_state = bh_orig->b_state; +#ifdef HIGHMEM_DEBUG bh->b_flushtime = jiffies; bh->b_next_free = NULL; bh->b_prev_free = NULL; /* bh->b_this_page */ bh->b_reqnext = NULL; bh->b_pprev = NULL; +#endif /* bh->b_page */ if (rw == WRITE) { bh->b_end_io = bounce_end_io_write; @@ -274,7 +280,9 @@ bh->b_end_io = bounce_end_io_read; bh->b_private = (void *)bh_orig; bh->b_rsector = bh_orig->b_rsector; +#ifdef HIGHMEM_DEBUG memset(&bh->b_wait, -1, sizeof(bh->b_wait)); +#endif return bh; }
(side note: right now HIGHMEM_DEBUG is enabled by default and that's ok of course)
And here it is an update that is now supposed to work with highmem machines as well:
ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/patches/v2.4/2.4.4pre7/rawio-6
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