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| author |   Ryan Roberts <ryan.roberts@arm.com> | 2023-12-01 16:10:45 +0000 |
|---|---|---|
| committer |   Andrew Morton <akpm@linux-foundation.org> | 2023-12-12 10:57:06 -0800 |
| commit | ec056cef76a525706601b32048f174f9bea72c7c (patch) | |
| tree | 1f20c7758389b12221fd1e17c4e8f01155372907 /mm/internal.h | |
| parent | mm: memory: use folio_prealloc() in wp_page_copy() (diff) | |
| download | wireguard-linux-ec056cef76a525706601b32048f174f9bea72c7c.tar.xz wireguard-linux-ec056cef76a525706601b32048f174f9bea72c7c.zip | |
mm/readahead: do not allow order-1 folio
The THP machinery does not support order-1 folios because it requires meta
data spanning the first 3 `struct page`s. So order-2 is the smallest
large folio that we can safely create.
There was a theoretical bug whereby if ra->size was 2 or 3 pages (due to
the device-specific bdi->ra_pages being set that way), we could end up
with order = 1. Fix this by unconditionally checking if the preferred
order is 1 and if so, set it to 0. Previously this was done in a few
specific places, but with this refactoring it is done just once,
unconditionally, at the end of the calculation.
This is a theoretical bug found during review of the code; I have no
evidence to suggest this manifests in the real world (I expect all
device-specific ra_pages values are much bigger than 3).
Link: https://lkml.kernel.org/r/20231201161045.3962614-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/internal.h')
0 files changed, 0 insertions, 0 deletions