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Add support for DISCARD to ZVOLs.

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DISCARD (REQ_DISCARD, BLKDISCARD) is useful for thin provisioning.
It allows ZVOL clients to discard (unmap, trim) block ranges from
a ZVOL, thus optimizing disk space usage by allowing a ZVOL to
shrink instead of just grow.

We can't use zfs_space() or zfs_freesp() here, since these functions
only work on regular files, not volumes. Fortunately we can use the
low-level function dmu_free_long_range() which does exactly what we
want.

Currently the discard operation is not added to the log. That's not
a big deal since losing discard requests cannot result in data
corruption. It would however result in disk space usage higher than
it should be. Thus adding log support to zvol_discard() is probably
a good idea for a future improvement.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Etienne Dechamps
2011-09-02 15:23:12 +02:00
committed by Brian Behlendorf
parent cb2d19010d
commit 30930fba21
60 changed files with 273 additions and 0 deletions
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configure
Vendored
+138
View File
@@ -14151,6 +14151,75 @@ $as_echo "no" >&6; }
fi
rm -Rf build
EXTRA_KCFLAGS="$tmp_flags"
{ $as_echo "$as_me:$LINENO: checking whether blk_queue_discard() is available" >&5
$as_echo_n "checking whether blk_queue_discard() is available... " >&6; }
tmp_flags="$EXTRA_KCFLAGS"
EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
cat confdefs.h - <<_ACEOF >conftest.c
/* confdefs.h. */
_ACEOF
cat confdefs.h >>conftest.$ac_ext
cat >>conftest.$ac_ext <<_ACEOF
/* end confdefs.h. */
#include <linux/blkdev.h>
int
main (void)
{
struct request_queue *q = NULL;
(void) blk_queue_discard(q);
;
return 0;
}
_ACEOF
rm -Rf build && mkdir -p build
echo "obj-m := conftest.o" >build/Makefile
if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
{ (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
(eval $ac_try) 2>&5
ac_status=$?
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
{ (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
(eval $ac_try) 2>&5
ac_status=$?
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); }; }; then
{ $as_echo "$as_me:$LINENO: result: yes" >&5
$as_echo "yes" >&6; }
cat >>confdefs.h <<\_ACEOF
#define HAVE_BLK_QUEUE_DISCARD 1
_ACEOF
else
$as_echo "$as_me: failed program was:" >&5
sed 's/^/| /' conftest.$ac_ext >&5
{ $as_echo "$as_me:$LINENO: result: no" >&5
$as_echo "no" >&6; }
fi
rm -Rf build
@@ -19969,6 +20038,75 @@ $as_echo "no" >&6; }
fi
rm -Rf build
EXTRA_KCFLAGS="$tmp_flags"
{ $as_echo "$as_me:$LINENO: checking whether blk_queue_discard() is available" >&5
$as_echo_n "checking whether blk_queue_discard() is available... " >&6; }
tmp_flags="$EXTRA_KCFLAGS"
EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
cat confdefs.h - <<_ACEOF >conftest.c
/* confdefs.h. */
_ACEOF
cat confdefs.h >>conftest.$ac_ext
cat >>conftest.$ac_ext <<_ACEOF
/* end confdefs.h. */
#include <linux/blkdev.h>
int
main (void)
{
struct request_queue *q = NULL;
(void) blk_queue_discard(q);
;
return 0;
}
_ACEOF
rm -Rf build && mkdir -p build
echo "obj-m := conftest.o" >build/Makefile
if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
{ (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
(eval $ac_try) 2>&5
ac_status=$?
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
{ (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
(eval $ac_try) 2>&5
ac_status=$?
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); }; }; then
{ $as_echo "$as_me:$LINENO: result: yes" >&5
$as_echo "yes" >&6; }
cat >>confdefs.h <<\_ACEOF
#define HAVE_BLK_QUEUE_DISCARD 1
_ACEOF
else
$as_echo "$as_me: failed program was:" >&5
sed 's/^/| /' conftest.$ac_ext >&5
{ $as_echo "$as_me:$LINENO: result: no" >&5
$as_echo "no" >&6; }
fi
rm -Rf build