Linux compat: Minimum kernel version 3.10

Increase the minimum supported kernel version from 2.6.32 to 3.10.
This removes support for the following Linux enterprise distributions.

    Distribution     | Kernel | End of Life
    ---------------- | ------ | -------------
    Ubuntu 12.04 LTS | 3.2    | Apr 28, 2017
    SLES 11          | 3.0    | Mar 32, 2019
    RHEL / CentOS 6  | 2.6.32 | Nov 30, 2020

The following changes were made as part of removing support.

* Updated `configure` to enforce a minimum kernel version as
  specified in the META file (Linux-Minimum: 3.10).

    configure: error:
        *** Cannot build against kernel version 2.6.32.
        *** The minimum supported kernel version is 3.10.

* Removed all `configure` kABI checks and matching C code for
  interfaces which solely predate the Linux 3.10 kernel.

* Updated all `configure` kABI checks to fail when an interface is
  missing which was in the 3.10 kernel up to the latest 5.1 kernel.
  Removed the HAVE_* preprocessor defines for these checks and
  updated the code to unconditionally use the verified interface.

* Inverted the detection logic in several kABI checks to match
  the new interface as it appears in 3.10 and newer and not the
  legacy interface.

* Consolidated the following checks in to individual files. Due
  the large number of changes in the checks it made sense to handle
  this now.  It would be desirable to group other related checks in
  the same fashion, but this as left as future work.

  - config/kernel-blkdev.m4 - Block device kABI checks
  - config/kernel-blk-queue.m4 - Block queue kABI checks
  - config/kernel-bio.m4 - Bio interface kABI checks

* Removed the kABI checks for sops->nr_cached_objects() and
  sops->free_cached_objects().  These interfaces are currently unused.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #9566

module/os/linux/spl/spl-cred.c

@@ -27,11 +27,7 @@
 #include <sys/cred.h>
 
 static int
-#ifdef HAVE_KUIDGID_T
 cr_groups_search(const struct group_info *group_info, kgid_t grp)
-#else
-cr_groups_search(const struct group_info *group_info, gid_t grp)
-#endif
 {
 	unsigned int left, right, mid;
 	int cmp;

module/os/linux/spl/spl-kmem-cache.c

@@ -1030,11 +1030,6 @@ spl_kmem_cache_create(char *name, size_t size, size_t align,
 			goto out;
 		}
 
-#if defined(HAVE_KMEM_CACHE_ALLOCFLAGS)
-		skc->skc_linux_cache->allocflags |= __GFP_COMP;
-#elif defined(HAVE_KMEM_CACHE_GFPFLAGS)
-		skc->skc_linux_cache->gfpflags |= __GFP_COMP;
-#endif
 		skc->skc_flags |= KMC_NOMAGAZINE;
 	}
 

module/os/linux/spl/spl-proc.c

@@ -712,9 +712,6 @@ static struct ctl_table spl_dir[] = {
 
 static struct ctl_table spl_root[] = {
 	{
-#ifdef HAVE_CTL_NAME
-	.ctl_name = CTL_KERN,
-#endif
 	.procname = "kernel",
 	.mode = 0555,
 	.child = spl_dir,

module/os/linux/spl/spl-vnode.c

@@ -48,17 +48,8 @@ spl_filp_fallocate(struct file *fp, int mode, loff_t offset, loff_t len)
 {
 	int error = -EOPNOTSUPP;
 
-#ifdef HAVE_FILE_FALLOCATE
 	if (fp->f_op->fallocate)
 		error = fp->f_op->fallocate(fp, mode, offset, len);
-#else
-#ifdef HAVE_INODE_FALLOCATE
-	if (fp->f_dentry && fp->f_dentry->d_inode &&
-	    fp->f_dentry->d_inode->i_op->fallocate)
-		error = fp->f_dentry->d_inode->i_op->fallocate(
-		    fp->f_dentry->d_inode, mode, offset, len);
-#endif /* HAVE_INODE_FALLOCATE */
-#endif /* HAVE_FILE_FALLOCATE */
 
 	return (error);
 }
@@ -66,11 +57,7 @@ spl_filp_fallocate(struct file *fp, int mode, loff_t offset, loff_t len)
 static int
 spl_filp_fsync(struct file *fp, int sync)
 {
-#ifdef HAVE_2ARGS_VFS_FSYNC
 	return (vfs_fsync(fp, sync));
-#else
-	return (vfs_fsync(fp, (fp)->f_dentry, sync));
-#endif /* HAVE_2ARGS_VFS_FSYNC */
 }
 
 static ssize_t
@@ -456,31 +443,6 @@ int vn_space(vnode_t *vp, int cmd, struct flock *bfp, int flag,
 	if (error == 0)
 		return (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)
-				return (0);
-		}
-		--end;
-
-		vp->v_file->f_dentry->d_inode->i_op->truncate_range(
-		    vp->v_file->f_dentry->d_inode, bfp->l_start, end);
-
-		return (0);
-	}
-#endif
-
 	return (error);
 }
 EXPORT_SYMBOL(vn_space);

module/os/linux/spl/spl-zlib.c

@@ -196,7 +196,7 @@ spl_zlib_init(void)
 {
 	int size;
 
-	size = MAX(spl_zlib_deflate_workspacesize(MAX_WBITS, MAX_MEM_LEVEL),
+	size = MAX(zlib_deflate_workspacesize(MAX_WBITS, MAX_MEM_LEVEL),
 	    zlib_inflate_workspacesize());
 
 	zlib_workspace_cache = kmem_cache_create(