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dax: check for data cache aliasing at runtime

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Replace the following fs/Kconfig:FS_DAX dependency:

  depends on !(ARM || MIPS || SPARC)

By a runtime check within alloc_dax(). This runtime check returns
ERR_PTR(-EOPNOTSUPP) if the @ops parameter is non-NULL (which means
the kernel is using an aliased mapping) on an architecture which
has data cache aliasing.

Change the return value from NULL to PTR_ERR(-EOPNOTSUPP) for
CONFIG_DAX=n for consistency.

This is done in preparation for using cpu_dcache_is_aliasing() in a
following change which will properly support architectures which detect
data cache aliasing at runtime.

Link: https://lkml.kernel.org/r/20240215144633.96437-8-mathieu.desnoyers@efficios.com
Fixes: d92576f116 ("dax: does not work correctly with virtual aliasing caches")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Michael Sclafani <dm-devel@lists.linux.dev>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Mathieu Desnoyers 2024-02-15 09:46:31 -05:00 committed by Andrew Morton
parent 562ce8285b
commit 1df4ca0155
2 changed files with 10 additions and 1 deletions
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10
drivers/dax/super.c
View file

@ -451,6 +451,16 @@ struct dax_device *alloc_dax(void *private, const struct dax_operations *ops)
dev_t devt;
int minor;
/*
* Unavailable on architectures with virtually aliased data caches,
* except for device-dax (NULL operations pointer), which does
* not use aliased mappings from the kernel.
*/
if (ops && (IS_ENABLED(CONFIG_ARM) ||
IS_ENABLED(CONFIG_MIPS) ||
IS_ENABLED(CONFIG_SPARC)))
return ERR_PTR(-EOPNOTSUPP);
if (WARN_ON_ONCE(ops && !ops->zero_page_range))
return ERR_PTR(-EINVAL);

1
fs/Kconfig
View file

@ -60,7 +60,6 @@ endif # BLOCK
config FS_DAX
bool "File system based Direct Access (DAX) support"
depends on MMU
depends on !(ARM || MIPS || SPARC)
depends on ZONE_DEVICE || FS_DAX_LIMITED
select FS_IOMAP
select DAX