Messages in this thread | | | Subject | Re: [PATCH 18/25] btrfs: Use readahead_batch_length | From | John Hubbard <> | Date | Thu, 17 Dec 2020 01:15:10 -0800 |
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On 12/16/20 10:23 AM, Matthew Wilcox (Oracle) wrote: > Implement readahead_batch_length() to determine the number of bytes in > the current batch of readahead pages and use it in btrfs. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- > fs/btrfs/extent_io.c | 6 ++---- > include/linux/pagemap.h | 9 +++++++++ > 2 files changed, 11 insertions(+), 4 deletions(-) > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index 6e3b72e63e42..42936a83a91b 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -4436,10 +4436,8 @@ void extent_readahead(struct readahead_control *rac) > int nr; > > while ((nr = readahead_page_batch(rac, pagepool))) { > - u64 contig_start = page_offset(pagepool[0]); > - u64 contig_end = page_offset(pagepool[nr - 1]) + PAGE_SIZE - 1; > - > - ASSERT(contig_start + nr * PAGE_SIZE - 1 == contig_end); > + u64 contig_start = readahead_pos(rac); > + u64 contig_end = contig_start + readahead_batch_length(rac);
Something in this tiny change is breaking btrfs: it hangs my Fedora 33 test system (which changed over to btrfs) on boot. I haven't quite figured out what's really wrong, but git bisect lands here, *and* turning the whole extent_readahead() function into a no-op (on top of the whole series) allows everything to work once again.
Sorry for not actually solving the root cause, but I figured you'd be able to jump straight to the answer, with the above information, so I'm sending it out early.
thanks, -- John Hubbard NVIDIA
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