Add interface for file hole punching.

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.
dechamps · Sep 3, 2012 · 0c0cb0d · 0c0cb0d
1 parent ac8ca67
commit 0c0cb0d
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diff --git a/config/spl-build.m4 b/config/spl-build.m4
@@ -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_FALLOC_FL_PUNCH_HOLE
 	SPL_AC_FS_STRUCT_SPINLOCK
 	SPL_AC_CRED_STRUCT
 	SPL_AC_GROUPS_SEARCH
@@ -1992,6 +1993,28 @@ AC_DEFUN([SPL_AC_2ARGS_VFS_FSYNC], [
 	])
 ])
 
+dnl #
+dnl # 2.6.38 API change,
+dnl # check if file hole punching is available
+dnl #
+AC_DEFUN([SPL_AC_FALLOC_FL_PUNCH_HOLE],
+	[AC_MSG_CHECKING([whether kernel defines FALLOC_FL_PUNCH_HOLE])
+	SPL_LINUX_TRY_COMPILE([
+		#include <linux/fs.h>
+		#include <linux/falloc.h>
+	],[
+		#ifndef FALLOC_FL_PUNCH_HOLE
+		#error FALLOC_FL_PUNCH_HOLE is undefined
+		#endif
+	],[
+		AC_MSG_RESULT([yes])
+		AC_DEFINE(HAVE_FALLOC_FL_PUNCH_HOLE, 1,
+		          [kernel defines FALLOC_FL_PUNCH_HOLE])
+	],[
+		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

diff --git a/include/sys/vnode.h b/include/sys/vnode.h
@@ -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

diff --git a/module/spl/spl-vnode.c b/module/spl/spl-vnode.c
@@ -25,6 +25,7 @@
 \*****************************************************************************/
 
 #include <sys/vnode.h>
+#include <linux/falloc.h>
 #include <spl-debug.h>
 
 #ifdef SS_DEBUG_SUBSYS
@@ -510,6 +511,39 @@ 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)
+{
+	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);
+
+#ifndef HAVE_FALLOC_FL_PUNCH_HOLE
+
+	SRETURN(-EOPNOTSUPP);
+
+#else
+
+	if (!vp->v_file->f_op->fallocate)
+		SRETURN(-EOPNOTSUPP);
+
+	/*
+	 * TODO: on some older kernel versions the interface is a
+	 * "truncate_range" inode operation.
+	 */
+	SRETURN(-vp->v_file->f_op->fallocate(vp->v_file,
+	    FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
+	    bfp->l_start, bfp->l_len));
+
+#endif
+}
+EXPORT_SYMBOL(vn_space);
+
 /* Function must be called while holding the vn_file_lock */
 static file_t *
 file_find(int fd)