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| author | Jan Kara <jack@suse.cz> | 2021-06-29 05:35:04 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-07-14 17:53:25 +0300 |
| commit | a87a201989ecbec6a11dab3203ac1599eee0d72b (patch) | |
| tree | 8c9c904095a01927c8ff8f72cb0e26094b6c7682 /fs/dax.c | |
| parent | 6ea84116b3fe69e336d1abede43915789e5291b6 (diff) | |
| download | linux-a87a201989ecbec6a11dab3203ac1599eee0d72b.tar.xz | |
dax: fix ENOMEM handling in grab_mapping_entry()
[ 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: b15cd800682f ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'fs/dax.c')
| -rw-r--r-- | fs/dax.c | 3 |
1 files changed, 2 insertions, 1 deletions
@@ -477,10 +477,11 @@ static void *grab_mapping_entry(struct xa_state *xas, struct address_space *mapping, unsigned int order) { unsigned long index = xas->xa_index; - bool pmd_downgrade = false; /* splitting PMD entry into PTE entries? */ + bool pmd_downgrade; /* splitting PMD entry into PTE entries? */ void *entry; retry: + pmd_downgrade = false; xas_lock_irq(xas); entry = get_unlocked_entry(xas, order); |