[PATCH] holepunch: fix disconnected pages after second truncate

shmem_truncate_range has its own truncate_inode_pages_range, to free any pages
racily instantiated while it was in progress: a SHMEM_PAGEIN flag is set when
this might have happened.  But holepunching gets no chance to clear that flag
at the start of vmtruncate_range, so it's always set (unless a truncate came
just before), so holepunch almost always does this second
truncate_inode_pages_range.

shmem holepunch has unlikely swap<->file races hereabouts whatever we do
(without a fuller rework than is fit for this release): I was going to skip
the second truncate in the punch_hole case, but Miklos points out that would
make holepunch correctness more vulnerable to swapoff.  So keep the second
truncate, but follow it by an unmap_mapping_range to eliminate the
disconnected pages (freed from pagecache while still mapped in userspace) that
it might have left behind.

Signed-off-by: Hugh Dickins <[email protected]>
Cc: Miklos Szeredi <[email protected]>
Cc: Badari Pulavarty <[email protected]>
Cc: Nick Piggin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions