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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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22
config/spl-build.m4
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

6
include/sys/vnode.h
View File

@ -66,6 +66,9 @@
#define FNODSYNC 0x10000 /* fsync pseudo flag */
#define FNOFOLLOW 0x20000 /* don't follow symlinks */
#define F_FREESP 11 /* Free file space */
/*
* The vnode AT_ flags are mapped to the Linux ATTR_* flags.
* This allows them to be used safely with an iattr structure.
@ -185,6 +188,8 @@ extern int vn_remove(const char *path, uio_seg_t seg, int flags);
extern int vn_rename(const char *path1, const char *path2, int x1);
extern int vn_getattr(vnode_t *vp, vattr_t *vap, int flags, void *x3, void *x4);
extern int vn_fsync(vnode_t *vp, int flags, void *x3, void *x4);
extern int vn_space(vnode_t *vp, int cmd, struct flock *bfp, int flag,
offset_t offset, void *x6, void *x7);
extern file_t *vn_getf(int fd);
extern void vn_releasef(int fd);
extern int vn_set_pwd(const char *filename);
@ -197,6 +202,7 @@ void spl_vn_fini(void);
#define VOP_SEEK vn_seek
#define VOP_GETATTR vn_getattr
#define VOP_FSYNC vn_fsync
#define VOP_SPACE vn_space
#define VOP_PUTPAGE(vp, o, s, f, x1, x2) ((void)0)
#define vn_is_readonly(vp) 0
#define getf vn_getf

53
module/spl/spl-vnode.c
View File

@ -25,6 +25,7 @@
\*****************************************************************************/
#include <sys/vnode.h>
#include <linux/falloc.h>
#include <spl-debug.h>
#ifdef SS_DEBUG_SUBSYS
@ -510,6 +511,58 @@ int vn_fsync(vnode_t *vp, int flags, void *x3, void *x4)
} /* vn_fsync() */
EXPORT_SYMBOL(vn_fsync);
int vn_space(vnode_t *vp, int cmd, struct flock *bfp, int flag,
offset_t offset, void *x6, void *x7)
{
int error = EOPNOTSUPP;
SENTRY;
if (cmd != F_FREESP || bfp->l_whence != 0)
SRETURN(EOPNOTSUPP);
ASSERT(vp);
ASSERT(vp->v_file);
ASSERT(bfp->l_start >= 0 && bfp->l_len > 0);
#ifdef FALLOC_FL_PUNCH_HOLE
if (vp->v_file->f_op->fallocate) {
error = -vp->v_file->f_op->fallocate(vp->v_file,
FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
bfp->l_start, bfp->l_len);
if (!error)
SRETURN(0);
}
#endif
#ifdef HAVE_INODE_TRUNCATE_RANGE
if (vp->v_file->f_dentry && vp->v_file->f_dentry->d_inode &&
vp->v_file->f_dentry->d_inode->i_op &&
vp->v_file->f_dentry->d_inode->i_op->truncate_range) {
off_t end = bfp->l_start + bfp->l_len;
/*
* Judging from the code in shmem_truncate_range(),
* it seems the kernel expects the end offset to be
* inclusive and aligned to the end of a page.
*/
if (end % PAGE_SIZE != 0) {
end &= ~(off_t)(PAGE_SIZE - 1);
if (end <= bfp->l_start)
SRETURN(0);
}
--end;
vp->v_file->f_dentry->d_inode->i_op->truncate_range(
vp->v_file->f_dentry->d_inode,
bfp->l_start, end
);
SRETURN(0);
}
#endif
SRETURN(error);
}
EXPORT_SYMBOL(vn_space);
/* Function must be called while holding the vn_file_lock */
static file_t *
file_find(int fd)