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Add interface for file hole punching.

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This adds an interface to "punch holes" (deallocate space) in VFS
files. The interface is identical to the Solaris VOP_SPACE interface.
This interface is necessary for TRIM support on file vdevs.

This is implemented using Linux fallocate(FALLOC_FL_PUNCH_HOLE), which
was introduced in 2.6.38. For a brief time before 2.6.38 this was done
using the truncate_range inode operation, which was quickly deprecated.
This patch only supports FALLOC_FL_PUNCH_HOLE.

This adds support for the truncate_range() inode operation to
VOP_SPACE() for file hole punching. This API is deprecated and removed
in 3.5, so it's only useful for old kernels.

On tmpfs, the truncate_range() inode operation translates to
shmem_truncate_range(). Unfortunately, this function expects the end
offset to be inclusive and aligned to the end of a page. If it is not,
the kernel will stop with a BUG_ON().

This patch fixes the issue by adapting to the constraints set forth by
shmem_truncate_range().

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #168
This commit is contained in:
Etienne Dechamps
2012-09-03 14:56:26 +02:00
committed by Brian Behlendorf
parent a6c6839a88
commit bbdc6ae495
3 changed files with 81 additions and 0 deletions
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config/spl-build.m4
+22
View File
@@ -72,6 +72,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
SPL_AC_4ARGS_VFS_RENAME
SPL_AC_VFS_FSYNC
SPL_AC_2ARGS_VFS_FSYNC
SPL_AC_INODE_TRUNCATE_RANGE
SPL_AC_FS_STRUCT_SPINLOCK
SPL_AC_CRED_STRUCT
SPL_AC_GROUPS_SEARCH
@@ -1992,6 +1993,27 @@ AC_DEFUN([SPL_AC_2ARGS_VFS_FSYNC], [
])
])
dnl #
dnl # 3.5 API change,
dnl # inode_operations.truncate_range removed
dnl # (deprecated in favor of FALLOC_FL_PUNCH_HOLE)
dnl #
AC_DEFUN([SPL_AC_INODE_TRUNCATE_RANGE], [
AC_MSG_CHECKING([whether truncate_range() inode operation is available])
SPL_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
struct inode_operations ops;
ops.truncate_range = NULL;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_INODE_TRUNCATE_RANGE, 1,
[truncate_range() inode operation is available])
],[
AC_MSG_RESULT(no)
])
]))
dnl #
dnl # 2.6.33 API change. Also backported in RHEL5 as of 2.6.18-190.el5.
dnl # Earlier versions of rwsem_is_locked() were inline and had a race