Re: [PATCH v2 0/7] fs/buffer: split pagecache lookups into atomic or blocking

[Luis Chamberlain <mcgrof@kernel.org>]

On Thu, Apr 17, 2025 at 06:59:14PM -0700, Davidlohr Bueso wrote:
> Hello,
> 
> Changes from v1: rebased on top of vfs.fixes (Christian).
> 
> This is a respin of the series[0] to address the sleep in atomic scenarios for
> noref migration with large folios, introduced in:
> 
>       3c20917120ce61 ("block/bdev: enable large folio support for large logical block sizes")
> 
> The main difference is that it removes the first patch and moves the fix (reducing
> the i_private_lock critical region in the migration path) to the final patch, which
> also introduces the new BH_Migrate flag. It also simplifies the locking scheme in
> patch 1 to avoid folio trylocking in the atomic lookup cases. So essentially blocking
> users will take the folio lock and hence wait for migration, and otherwise nonblocking
> callers will bail the lookup if a noref migration is on-going. Blocking callers
> will also benefit from potential performance gains by reducing contention on the
> spinlock for bdev mappings.
> 
> Applies against latest vfs.fixes. Please consider for Linus' tree.
> 
> Patch 1: carves a path for callers that can block to take the folio lock.
> Patch 2: adds sleeping flavors to pagecache lookups, no users.
> Patches 3-6: converts to the new call, where possible.
> Patch 7: does the actual sleep in atomic fix.
> 
> Thanks!

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Tested-by: kdevops@lists.linux.dev # [0] [1]
Link: https://kdevops.org/ext4/v6.15-rc2.html # [0]
Link: https://lore.kernel.org/all/aAAEvcrmREWa1SKF@bombadil.infradead.org/ # [1]

  Luis