mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-10 02:12:00 -04:00
1a14e3779d
grab_mapping_entry() has a bug in handling of ENOMEM condition. Suppose
we have a PMD entry at index i which we are downgrading to a PTE entry.
grab_mapping_entry() will set pmd_downgrade to true, lock the entry, clear
the entry in xarray, and decrement mapping->nrpages. The it will call:
entry = dax_make_entry(pfn_to_pfn_t(0), flags);
dax_lock_entry(xas, entry);
which inserts new PTE entry into xarray. However this may fail allocating
the new node. We handle this by:
if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM))
goto retry;
however pmd_downgrade stays set to true even though 'entry' returned from
get_unlocked_entry() will be NULL now. And we will go again through the
downgrade branch. This is mostly harmless except that mapping->nrpages is
decremented again and we temporarily have an invalid entry stored in
xarray. Fix the problem by setting pmd_downgrade to false each time we
lookup the entry we work with so that it matches the entry we found.
Link: https://lkml.kernel.org/r/20210622160015.18004-1-jack@suse.cz
Fixes: b15cd80068 ("dax: Convert page fault handlers to XArray")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.