• Hugh Dickins's avatar
    mm for fs: add truncate_pagecache_range() · 623e3db9
    Hugh Dickins authored
    Holepunching filesystems ext4 and xfs are using truncate_inode_pages_range
    but forgetting to unmap pages first (ocfs2 remembers).  This is not really
    a bug, since races already require truncate_inode_page() to handle that
    case once the page is locked; but it can be very inefficient if the file
    being punched happens to be mapped into many vmas.
    Provide a drop-in replacement truncate_pagecache_range() which does the
    unmapping pass first, handling the awkward mismatch between arguments to
    truncate_inode_pages_range() and arguments to unmap_mapping_range().
    Note that holepunching does not unmap privately COWed pages in the range:
    POSIX requires that we do so when truncating, but it's hard to justify,
    difficult to implement without an i_size cutoff, and no filesystem is
    attempting to implement it.
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Cc: "Theodore Ts'o" <tytso@mit.edu>
    Cc: Andreas Dilger <adilger.kernel@dilger.ca>
    Cc: Mark Fasheh <mfasheh@suse.com>
    Cc: Joel Becker <jlbec@evilplan.org>
    Cc: Ben Myers <bpm@sgi.com>
    Cc: Alex Elder <elder@kernel.org>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
truncate.c 19.7 KB