ACK: [X/B/D/E/F][PATCH 0/1] bcache: fix oops for block size > page size
andrea.righi at canonical.com
Wed Jul 8 07:11:52 UTC 2020
On Tue, Jul 07, 2020 at 12:32:49PM -0300, Mauricio Faria de Oliveira wrote:
> BugLink: https://bugs.launchpad.net/bugs/1867916
> This is not high priority, as the regression surface
> is limited by user-specific configuration; they will
> be provided w/ test kernel builds for the time being.
> Please review/fix when convenient.
> * Users of bcache who manually specified a block size
> greater than the page size when creating the device
> with 'make-bcache' started to hit a kernel BUG/oops
> after kernel upgrades. (This is not widely used.)
> * The issue has been exposed with commit ad6bf88a6c19
> ("block: fix an integer overflow in logical block size")
> because it increased the range of values accepted as
> logical block size, which used to overflow to zero,
> and thus receive a default of 512 via block layer.
> * The issue existed previously, but with fewer values
> exposed (e.g. 8k, 16k, 32k); the regression reports
> happened with larger values (512k) for RAID stripes.
> * The upstream commit dcacbc1242c7 ("bcache: check and
> adjust logical block size for backing devices") checks
> the block size and adjusts it if needed, to the value
> of the underlying device's logical block size.
> * It is merged as of v5.8-rcN, and sent to v5.7 stable.
> [Test Case]
> * Run make-bcache with block size greater than page size.
> $ sudo make-bcache --bdev $DEV --block 8k
> * Expected results: bcache device registered; no BUG/oops.
> * Detailed steps on LP bug comment.
> [Regression Potential]
> * Restricted to users who specify a bcache block size
> greater than page size.
> * Regressions could theoretically manifest on bcache
> device probe/register, if the underlying device's
> logical block size for whatever triggers issues not
> seen previously with the overflow/default 512 bytes.
> [Other Info]
> * Unstable has the patch on both master and master-5.7.
> * Groovy should get it on rebase.
Upstream fix that solves a potential kernel BUG, reviewed by bcache
maintainer, also tested with positive result, all good to me.
Acked-by: Andrea Righi <andrea.righi at canonical.com>
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