• Hugh Dickins's avatar
    tmpfs: take control of its truncate_range · 94c1e62d
    Hugh Dickins authored
    2.6.35's new truncate convention gave tmpfs the opportunity to control
    its file truncation, no longer enforced from outside by vmtruncate().
    We shall want to build upon that, to handle pagecache and swap together.
    
    Slightly redefine the ->truncate_range interface: let it now be called
    between the unmap_mapping_range()s, with the filesystem responsible for
    doing the truncate_inode_pages_range() from it - just as the filesystem
    is nowadays responsible for doing that from its ->setattr.
    
    Let's rename shmem_notify_change() to shmem_setattr().  Instead of
    calling the generic truncate_setsize(), bring that code in so we can
    call shmem_truncate_range() - which will later be updated to perform its
    own variant of truncate_inode_pages_range().
    
    Remove the punch_hole unmap_mapping_range() from shmem_truncate_range():
    now that the COW's unmap_mapping_range() comes after ->truncate_range,
    there is no need to call it a third time.
    
    Export shmem_truncate_range() and add it to the list in shmem_fs.h, so
    that i915_gem_object_truncate() can call it explicitly in future; get
    this patch in first, then update drm/i915 once this is available (until
    then, i915 will just be doing the truncate_inode_pages() twice).
    
    Though introduced five years ago, no other filesystem is implementing
    ->truncate_range, and its only other user is madvise(,,MADV_REMOVE): we
    expect to convert it to fallocate(,FALLOC_FL_PUNCH_HOLE,,) shortly,
    whereupon ->truncate_range can be removed from inode_operations -
    shmem_truncate_range() will help i915 across that transition too.
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Cc: Christoph Hellwig <hch@infradead.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    94c1e62d
shmem_fs.h 2.33 KB