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author | Markus Stockhausen <stockhausen@collogia.de> | 2018-07-27 17:09:53 +0200 |
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committer | Jens Axboe <axboe@kernel.dk> | 2018-07-27 17:09:53 +0200 |
commit | dc30b96ab6d569060741572cf30517d3179429a8 (patch) | |
tree | 9b84c38b14a2064c82766d3beca0511820e4606c | |
parent | scsi: virtio_scsi: fix pi_bytes{out,in} on 4 KiB block size devices (diff) | |
download | linux-dc30b96ab6d569060741572cf30517d3179429a8.tar.xz linux-dc30b96ab6d569060741572cf30517d3179429a8.zip |
readahead: stricter check for bdi io_pages
ondemand_readahead() checks bdi->io_pages to cap the maximum pages
that need to be processed. This works until the readit section. If
we would do an async only readahead (async size = sync size) and
target is at beginning of window we expand the pages by another
get_next_ra_size() pages. Btrace for large reads shows that kernel
always issues a doubled size read at the beginning of processing.
Add an additional check for io_pages in the lower part of the func.
The fix helps devices that hard limit bio pages and rely on proper
handling of max_hw_read_sectors (e.g. older FusionIO cards). For
that reason it could qualify for stable.
Fixes: 9491ae4a ("mm: don't cap request size based on read-ahead setting")
Cc: stable@vger.kernel.org
Signed-off-by: Markus Stockhausen stockhausen@collogia.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r-- | mm/readahead.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/mm/readahead.c b/mm/readahead.c index 9f62b7151100..a59ea70527b9 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -386,6 +386,7 @@ ondemand_readahead(struct address_space *mapping, { struct backing_dev_info *bdi = inode_to_bdi(mapping->host); unsigned long max_pages = ra->ra_pages; + unsigned long add_pages; pgoff_t prev_offset; /* @@ -475,10 +476,17 @@ readit: * Will this read hit the readahead marker made by itself? * If so, trigger the readahead marker hit now, and merge * the resulted next readahead window into the current one. + * Take care of maximum IO pages as above. */ if (offset == ra->start && ra->size == ra->async_size) { - ra->async_size = get_next_ra_size(ra, max_pages); - ra->size += ra->async_size; + add_pages = get_next_ra_size(ra, max_pages); + if (ra->size + add_pages <= max_pages) { + ra->async_size = add_pages; + ra->size += add_pages; + } else { + ra->size = max_pages; + ra->async_size = max_pages >> 1; + } } return ra_submit(ra, mapping, filp); |