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@xxxxxxxxxxxxx>
---
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
