Shmem uses shmem_recalc_inode to update i_blocks when it allocates page,
undoes range or swaps. But mm can drop clean page without notifying
shmem. This makes fstat sometimes return out-of-date block size.
The problem can be partially solved when we add
inode_operations->getattr which calls shmem_recalc_inode to update
i_blocks for fstat.
shmem_recalc_inode also updates counter used by statfs and
vm_committed_as. For them the situation is not changed. They still
suffer from the discrepancy after dropping clean page and before the
function is called by aforementioned triggers.
Signed-off-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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