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c872674da7
[ Upstream commit 1a14e3779dd58c16b30e56558146e5cc850ba8b0 ]
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:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.