copy: fix copying of extents beyond the apparent file size

fallocate can allocate extents beyond EOF via FALLOC_FL_KEEP_SIZE.
Where there is a gap (hole) between the extents, and EOF is within
that gap, the final hole wasn't reproduced, resulting in silent
data corruption in the copied file (size too small).

* src/copy.c (extent_copy): Ensure we don't process extents
beyond the apparent file size, since processing and allocating
those is not currently supported.
* tests/cp/fiemap-extents.sh: Renamed from tests/cp/fiemap-empty.sh
and re-enable parts checking the extents at and beyond EOF.
* tests/local.mk: Reference the renamed test.
* NEWS: Mention the bug fix.
Fixes http://bugs.gnu.org/21790

5 files changed, 105 insertions, 104 deletions

diff --git a/NEWS b/NEWS
index 9f6bff213..298814613 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,11 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** Bug fixes
 
+  cp now correctly copies files with a hole at the end of the file,
+  and extents allocated beyond the apparent size of the file.
+  That combination resulted in the trailing hole not being reproduced.
+  [bug introduced in coreutils-8.10]
+
   ls no longer prematurely wraps lines when printing short file names.
   [bug introduced in 5.1.0]
 
diff --git a/src/copy.c b/src/copy.c
index dc1cd2904..6771bb53b 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -432,6 +432,20 @@ extent_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
               ext_len = 0;
             }
 
+          /* Truncate extent to EOF.  Extents starting after EOF are
+             treated as zero length extents starting right after EOF.
+             Generally this will trigger with an extent starting after
+             src_total_size, and result in creating a hole or zeros until EOF.
+             Though in a file in which extents have changed since src_total_size
+             was determined, we might have an extent spanning that size,
+             in which case we'll only copy data up to that size.  */
+          if (src_total_size < ext_start + ext_len)
+            {
+              if (src_total_size < ext_start)
+                ext_start = src_total_size;
+              ext_len = src_total_size - ext_start;
+            }
+
           ext_hole_size = ext_start - last_ext_start - last_ext_len;
 
           wrote_hole_at_eof = false;
@@ -495,14 +509,17 @@ extent_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
               off_t n_read;
               empty_extent = false;
               last_ext_len = ext_len;
+              bool read_hole;
 
               if ( ! sparse_copy (src_fd, dest_fd, buf, buf_size,
                                   sparse_mode == SPARSE_ALWAYS ? hole_size: 0,
                                   true, src_name, dst_name, ext_len, &n_read,
-                                  &wrote_hole_at_eof))
+                                  &read_hole))
                 goto fail;
 
               dest_pos = ext_start + n_read;
+              if (n_read)
+                wrote_hole_at_eof = read_hole;
             }
 
           /* If the file ends with unwritten extents not accounted for in the
diff --git a/tests/cp/fiemap-empty.sh b/tests/cp/fiemap-empty.sh
deleted file mode 100755
index b3b2cd72b..000000000
--- a/tests/cp/fiemap-empty.sh
+++ /dev/null
@@ -1,102 +0,0 @@
-#!/bin/sh
-# Test cp reads unwritten extents efficiently
-
-# Copyright (C) 2011-2015 Free Software Foundation, Inc.
-
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
-print_ver_ cp
-
-# FIXME: enable any part of this test that is still relevant,
-# or, if none are relevant (now that cp does not handle unwritten
-# extents), just remove the test altogether.
-# Note also if checking allocations may need to sync first on BTRFS at least
-skip_ 'disabled for now'
-
-touch fiemap_chk
-fiemap_capable_ fiemap_chk ||
-  skip_ 'this file system lacks FIEMAP support'
-rm fiemap_chk
-
-# TODO: rather than requiring $(fallocate), possible add
-# this functionality to truncate --alloc
-fallocate --help >/dev/null || skip_ 'The fallocate utility is required'
-fallocate -l 1 -n falloc.test ||
-  skip_ 'this file system lacks FALLOCATE support'
-rm falloc.test
-
-# Require more space than we'll actually use, so that
-# tests run in parallel do not run out of space.
-# Otherwise, with inadequate space, simply running the following
-# fallocate command would induce a temporary disk-full condition,
-# which would cause failure of unrelated tests run in parallel.
-require_file_system_bytes_free_ 800000000
-
-fallocate -l 600MiB space.test ||
-  skip_ 'this test needs at least 600MiB free space'
-
-# Disable this test on old BTRFS (e.g. Fedora 14)
-# which reports ordinary extents for unwritten ones.
-filefrag space.test || skip_ 'the 'filefrag' utility is missing'
-filefrag -v space.test | grep -F 'unwritten' > /dev/null ||
-  skip_ 'this file system does not report empty extents as "unwritten"'
-
-rm space.test
-
-# Ensure we read a large empty file quickly
-fallocate -l 300MiB empty.big || framework_failure_
-timeout 3 cp --sparse=always empty.big cp.test || fail=1
-test $(stat -c %s empty.big) = $(stat -c %s cp.test) || fail=1
-rm empty.big cp.test
-
-# Ensure we handle extents beyond file size correctly.
-# Note until we support fallocate, we will not maintain
-# the file allocation.  FIXME: amend this test when fallocate is supported.
-fallocate -l 10MiB -n unwritten.withdata || framework_failure_
-dd count=10 if=/dev/urandom conv=notrunc iflag=fullblock of=unwritten.withdata
-cp unwritten.withdata cp.test || fail=1
-test $(stat -c %s unwritten.withdata) = $(stat -c %s cp.test) || fail=1
-cmp unwritten.withdata cp.test || fail=1
-rm unwritten.withdata cp.test
-
-# The following to generate unaccounted extents followed by a hole, is not
-# supported by ext4 at least. The ftruncate discards all extents not
-# accounted for in the size.
-#  fallocate -l 10MiB -n unacc.withholes
-#  dd count=10 if=/dev/urandom conv=notrunc iflag=fullblock of=unacc.withholes
-#  truncate -s20M unacc.withholes
-
-# Ensure we handle a hole after empty extents correctly.
-# Since all extents are accounted for in the size,
-# we can maintain the allocation independently from
-# fallocate() support.
-fallocate -l 10MiB empty.withholes
-truncate -s 20M empty.withholes
-sectors_per_block=$(expr $(stat -c %o .) / 512)
-cp empty.withholes cp.test || fail=1
-test $(stat -c %s empty.withholes) = $(stat -c %s cp.test) || fail=1
-# These are usually equal but can vary by an IO block due to alignment
-alloc_diff=$(expr $(stat -c %b empty.withholes) - $(stat -c %b cp.test))
-alloc_diff=$(echo $alloc_diff | tr -d -- -) # abs()
-test $alloc_diff -le $sectors_per_block || fail=1
-# Again with SPARSE_ALWAYS
-cp --sparse=always empty.withholes cp.test || fail=1
-test $(stat -c %s empty.withholes) = $(stat -c %s cp.test) || fail=1
-# cp.test should take 0 space, but allowing for some systems
-# that store default extended attributes in data blocks
-test $(stat -c %b cp.test) -le $sectors_per_block || fail=1
-rm empty.withholes cp.test
-
-Exit $fail
diff --git a/tests/cp/fiemap-extents.sh b/tests/cp/fiemap-extents.sh
new file mode 100755
index 000000000..55ec5dfd8
--- /dev/null
+++ b/tests/cp/fiemap-extents.sh
@@ -0,0 +1,81 @@
+#!/bin/sh
+# Test cp handles extents correctly
+
+# Copyright (C) 2011-2015 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ cp
+
+require_sparse_support_
+
+touch fiemap_chk
+fiemap_capable_ fiemap_chk ||
+  skip_ 'this file system lacks FIEMAP support'
+rm fiemap_chk
+
+fallocate --help >/dev/null || skip_ 'The fallocate utility is required'
+touch falloc.test || framework_failure_
+fallocate -l 1 -o 0 -n falloc.test ||
+  skip_ 'this file system lacks FALLOCATE support'
+rm falloc.test
+
+# We don't currently handle unwritten extents specially
+if false; then
+# Require more space than we'll actually use, so that
+# tests run in parallel do not run out of space.
+# Otherwise, with inadequate space, simply running the following
+# fallocate command would induce a temporary disk-full condition,
+# which would cause failure of unrelated tests run in parallel.
+require_file_system_bytes_free_ 800000000
+
+fallocate -l 600MiB space.test ||
+  skip_ 'this test needs at least 600MiB free space'
+
+# Disable this test on old BTRFS (e.g. Fedora 14)
+# which reports ordinary extents for unwritten ones.
+filefrag space.test || skip_ 'the 'filefrag' utility is missing'
+filefrag -v space.test | grep -F 'unwritten' > /dev/null ||
+  skip_ 'this file system does not report empty extents as "unwritten"'
+
+rm space.test
+
+# Ensure we read a large empty file quickly
+fallocate -l 300MiB empty.big || framework_failure_
+timeout 3 cp --sparse=always empty.big cp.test || fail=1
+test $(stat -c %s empty.big) = $(stat -c %s cp.test) || fail=1
+rm empty.big cp.test
+fi
+
+# Ensure we handle extents beyond file size correctly.
+# Note until we support fallocate, we will not maintain
+# the file allocation.  FIXME: amend this test if fallocate is supported.
+# Note currently this only uses fiemap logic when the allocation (-l)
+# is smaller than the size, thus identifying the file as sparse.
+# Note the '-l 1' case is an effective noop, and just checks
+# a file with a trailing hole is copied correctly.
+for sparse_mode in always auto never; do
+  for alloc in '-l 4MiB ' '-l 1MiB -o 4MiB' '-l 1'; do
+    dd count=10 if=/dev/urandom iflag=fullblock of=unwritten.withdata
+    truncate -s 2MiB unwritten.withdata || framework_failure_
+    fallocate $alloc -n unwritten.withdata || framework_failure_
+    cp --sparse=$sparse_mode unwritten.withdata cp.test || fail=1
+    test $(stat -c %s unwritten.withdata) = $(stat -c %s cp.test) || fail=1
+    cmp unwritten.withdata cp.test || fail=1
+    rm unwritten.withdata cp.test
+  done
+done
+
+Exit $fail
diff --git a/tests/local.mk b/tests/local.mk
index adf96f015..89fdbb0bc 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -446,7 +446,7 @@ all_tests =					\
   tests/cp/existing-perm-dir.sh			\
   tests/cp/existing-perm-race.sh		\
   tests/cp/fail-perm.sh				\
-  tests/cp/fiemap-empty.sh			\
+  tests/cp/fiemap-extents.sh			\
   tests/cp/fiemap-FMR.sh			\
   tests/cp/fiemap-perf.sh			\
   tests/cp/fiemap-2.sh				\