--- a/usr/src/uts/common/fs/ufs/lufs.c	Fri Jun 19 12:13:15 2009 -0600
+++ b/usr/src/uts/common/fs/ufs/lufs.c	Fri Jun 19 11:32:47 2009 -0700
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
@@ -65,10 +65,12 @@
 /* Tunables */
 uint_t		ldl_maxlogsize	= LDL_MAXLOGSIZE;
 uint_t		ldl_minlogsize	= LDL_MINLOGSIZE;
+uint_t		ldl_softlogcap	= LDL_SOFTLOGCAP;
 uint32_t	ldl_divisor	= LDL_DIVISOR;
 uint32_t	ldl_mintransfer	= LDL_MINTRANSFER;
 uint32_t	ldl_maxtransfer	= LDL_MAXTRANSFER;
 uint32_t	ldl_minbufsize	= LDL_MINBUFSIZE;
+uint32_t	ldl_cgsizereq	= 0;
 
 /* Generation of header ids */
 static kmutex_t	genid_mutex;
@@ -656,7 +658,7 @@
  *	Assumes the file system is write locked and is not logging
  */
 static int
-lufs_alloc(struct ufsvfs *ufsvfsp, struct fiolog *flp, cred_t *cr)
+lufs_alloc(struct ufsvfs *ufsvfsp, struct fiolog *flp, size_t minb, cred_t *cr)
 {
 	int		error = 0;
 	buf_t		*bp = NULL;
@@ -689,7 +691,7 @@
 	ip = ufs_alloc_inode(ufsvfsp, UFSROOTINO);
 	ip->i_mode = IFSHAD;		/* make the dummy a shadow inode */
 	rw_enter(&ip->i_contents, RW_WRITER);
-	fno = contigpref(ufsvfsp, nb + fs->fs_bsize);
+	fno = contigpref(ufsvfsp, nb + fs->fs_bsize, minb);
 	error = alloc(ip, fno, fs->fs_bsize, &fno, cr);
 	if (error)
 		goto errout;
@@ -733,7 +735,7 @@
 	while (nb) {
 		error = alloc(ip, fno + fs->fs_frag, fs->fs_bsize, &fno, cr);
 		if (error) {
-			if (tb < ldl_minlogsize)
+			if (tb < minb)
 				goto errout;
 			error = 0;
 			break;
@@ -760,6 +762,12 @@
 		tb += fs->fs_bsize;
 		nb -= fs->fs_bsize;
 	}
+
+	if (tb < minb) {	/* Failed to reach minimum log size */
+		error = ENOSPC;
+		goto errout;
+	}
+
 	ebp->nbytes = (uint32_t)tb;
 	setsum(&ebp->chksum, (int32_t *)bp->b_un.b_addr, fs->fs_bsize);
 	UFS_BWRITE2(ufsvfsp, bp);
@@ -983,6 +991,10 @@
 	struct ulockfs	*ulp;
 	vfs_t		*vfsp = ufsvfsp->vfs_vfs;
 	uint64_t	tmp_nbytes_actual;
+	uint64_t	cg_minlogsize;
+	uint32_t	cgsize;
+	static int	minlogsizewarn = 0;
+	static int	maxlogsizewarn = 0;
 
 	/*
 	 * Check if logging is already enabled
@@ -1004,6 +1016,22 @@
 	flp->error = FIOLOG_ENONE;
 
 	/*
+	 * The size of the ufs log is determined using the following rules:
+	 *
+	 * 1) If no size is requested the log size is calculated as a
+	 *    ratio of the total file system size. By default this is
+	 *    1MB of log per 1GB of file system. This calculation is then
+	 *    capped at the log size specified by ldl_softlogcap.
+	 * 2) The log size requested may then be increased based on the
+	 *    number of cylinder groups contained in the file system.
+	 *    To prevent a hang the log has to be large enough to contain a
+	 *    single transaction that alters every cylinder group in the file
+	 *    system. This is calculated as cg_minlogsize.
+	 * 3) Finally a check is made that the log size requested is within
+	 *    the limits of ldl_minlogsize and ldl_maxlogsize.
+	 */
+
+	/*
 	 * Adjust requested log size
 	 */
 	flp->nbytes_actual = flp->nbytes_requested;
@@ -1011,7 +1039,59 @@
 		tmp_nbytes_actual =
 		    (((uint64_t)fs->fs_size) / ldl_divisor) << fs->fs_fshift;
 		flp->nbytes_actual = (uint_t)MIN(tmp_nbytes_actual, INT_MAX);
+		/*
+		 * The 1MB per 1GB log size allocation only applies up to
+		 * ldl_softlogcap size of log.
+		 */
+		flp->nbytes_actual = MIN(flp->nbytes_actual, ldl_softlogcap);
 	}
+
+	cgsize = ldl_cgsizereq ? ldl_cgsizereq : LDL_CGSIZEREQ(fs);
+
+	/*
+	 * Determine the log size required based on the number of cylinder
+	 * groups in the file system. The log has to be at least this size
+	 * to prevent possible hangs due to log space exhaustion.
+	 */
+	cg_minlogsize = cgsize * fs->fs_ncg;
+
+	/*
+	 * Ensure that the minimum log size isn't so small that it could lead
+	 * to a full log hang.
+	 */
+	if (ldl_minlogsize < LDL_MINLOGSIZE) {
+		ldl_minlogsize = LDL_MINLOGSIZE;
+		if (!minlogsizewarn) {
+			cmn_err(CE_WARN, "ldl_minlogsize too small, increasing "
+			    "to 0x%x", LDL_MINLOGSIZE);
+			minlogsizewarn = 1;
+		}
+	}
+
+	/*
+	 * Ensure that the maximum log size isn't greater than INT_MAX as the
+	 * logical log offset fields would overflow.
+	 */
+	if (ldl_maxlogsize > INT_MAX) {
+		ldl_maxlogsize = INT_MAX;
+		if (!maxlogsizewarn) {
+			cmn_err(CE_WARN, "ldl_maxlogsize too large, reducing "
+			    "to 0x%x", INT_MAX);
+			maxlogsizewarn = 1;
+		}
+	}
+
+	if (cg_minlogsize > ldl_maxlogsize) {
+		cmn_err(CE_WARN,
+		    "%s: reducing calculated log size from 0x%x to "
+		    "ldl_maxlogsize (0x%x).", fs->fs_fsmnt, (int)cg_minlogsize,
+		    ldl_maxlogsize);
+	}
+
+	cg_minlogsize = MAX(cg_minlogsize, ldl_minlogsize);
+	cg_minlogsize = MIN(cg_minlogsize, ldl_maxlogsize);
+
+	flp->nbytes_actual = MAX(flp->nbytes_actual, cg_minlogsize);
 	flp->nbytes_actual = MAX(flp->nbytes_actual, ldl_minlogsize);
 	flp->nbytes_actual = MIN(flp->nbytes_actual, ldl_maxlogsize);
 	flp->nbytes_actual = blkroundup(fs, flp->nbytes_actual);
@@ -1106,7 +1186,7 @@
 		goto recheck;
 	}
 
-	error = lufs_alloc(ufsvfsp, flp, cr);
+	error = lufs_alloc(ufsvfsp, flp, cg_minlogsize, cr);
 	if (error)
 		goto errout;
 

--- a/usr/src/uts/common/fs/ufs/ufs_alloc.c	Fri Jun 19 12:13:15 2009 -0600
+++ b/usr/src/uts/common/fs/ufs/ufs_alloc.c	Fri Jun 19 11:32:47 2009 -0700
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
@@ -68,6 +68,7 @@
 #include <fs/fs_subr.h>
 #include <sys/cmn_err.h>
 #include <sys/policy.h>
+#include <sys/fs/ufs_log.h>
 
 static ino_t	hashalloc();
 static daddr_t	fragextend();
@@ -75,6 +76,7 @@
 static daddr_t	alloccgblk();
 static ino_t	ialloccg();
 static daddr_t	mapsearch();
+static int	findlogstartcg();
 
 extern int	inside[], around[];
 extern uchar_t	*fragtbl[];
@@ -1944,12 +1946,13 @@
  * writing the ufs log file to, minimizing future disk head seeking
  */
 daddr_t
-contigpref(ufsvfs_t *ufsvfsp, size_t nb)
+contigpref(ufsvfs_t *ufsvfsp, size_t nb, size_t minb)
 {
 	struct fs	*fs	= ufsvfsp->vfs_fs;
 	daddr_t		nblk	= lblkno(fs, blkroundup(fs, nb));
+	daddr_t		minblk	= lblkno(fs, blkroundup(fs, minb));
 	daddr_t		savebno, curbno, cgbno;
-	int		cg, cgblks, savecg, savenblk, curnblk;
+	int		cg, cgblks, savecg, savenblk, curnblk, startcg;
 	uchar_t		*blksfree;
 	buf_t		*bp;
 	struct cg	*cgp;
@@ -1957,12 +1960,13 @@
 	savenblk = 0;
 	savecg = 0;
 	savebno = 0;
-	for (cg = 0; cg < fs->fs_ncg; ++cg) {
 
-		/* not enough free blks for a contig check */
-		if (fs->fs_cs(fs, cg).cs_nbfree < nblk)
-			continue;
+	if ((startcg = findlogstartcg(fs, nblk, minblk)) == -1)
+		cg = 0;	/* Nothing suitable found */
+	else
+		cg = startcg;
 
+	for (; cg < fs->fs_ncg; ++cg) {
 		/*
 		 * find the largest contiguous range in this cg
 		 */
@@ -1979,9 +1983,14 @@
 		cgbno = 0;
 		while (cgbno < cgblks && savenblk < nblk) {
 			/* find a free block */
-			for (; cgbno < cgblks; ++cgbno)
-				if (isblock(fs, blksfree, cgbno))
-					break;
+			for (; cgbno < cgblks; ++cgbno) {
+				if (isblock(fs, blksfree, cgbno)) {
+					if (startcg != -1)
+						goto done;
+					else
+						break;
+				}
+			}
 			curbno = cgbno;
 			/* count the number of free blocks */
 			for (curnblk = 0; cgbno < cgblks; ++cgbno) {
@@ -2001,6 +2010,13 @@
 			break;
 	}
 
+done:
+	if (startcg != -1) {
+		brelse(bp);
+		savecg = startcg;
+		savebno = cgbno;
+	}
+
 	/* convert block offset in cg to frag offset in cg */
 	savebno = blkstofrags(fs, savebno);
 
@@ -2009,3 +2025,78 @@
 
 	return (savebno);
 }
+
+/*
+ * The object of this routine is to find a start point for the UFS log.
+ * Ideally the space should be allocated from the smallest possible number
+ * of contiguous cylinder groups. This is found by using a sliding window
+ * technique. The smallest window of contiguous cylinder groups, which is
+ * still able to accommodate the target, is found by moving the window
+ * through the cylinder groups in a single pass. The end of the window is
+ * advanced until the space is accommodated, then the start is advanced until
+ * it no longer fits, the end is then advanced again and so on until the
+ * final cylinder group is reached. The first suitable instance is recorded
+ * and its starting cg number is returned.
+ *
+ * If we are not able to find a minimum amount of space, represented by
+ * minblk, or to do so uses more than the available extents, then return -1.
+ */
+
+int
+findlogstartcg(struct fs *fs, daddr_t requested, daddr_t minblk)
+{
+	int	 ncgs;		 /* number of cylinder groups */
+	daddr_t target;		 /* amount of space sought */
+	int	 cwidth, ctotal; /* current window width and total */
+	int	 bwidth, btotal; /* best window width and total so far */
+	int	 s;	/* index of the first element in the current window */
+	int	 e;	/* index of the first element + the width */
+			/*  (i.e. 1 + index of last element) */
+	int	 bs; /* index of the first element in the best window so far */
+	int	 header, max_extents;
+
+	target = requested;
+	ncgs = fs->fs_ncg;
+
+	header = sizeof (extent_block_t) - sizeof (extent_t);
+	max_extents = ((fs->fs_bsize)-header) / sizeof (extent_t);
+	cwidth = ctotal = 0;
+	btotal = -1;
+	bwidth = ncgs;
+	s = e = 0;
+	while (e < ncgs) {
+	/* Advance the end of the window until it accommodates the target. */
+		while (ctotal < target && e < ncgs) {
+			ctotal += fs->fs_cs(fs, e).cs_nbfree;
+			e++;
+		}
+
+		/*
+		 * Advance the start of the window until it no longer
+		 * accommodates the target.
+		 */
+		while (ctotal >= target && s < e) {
+			/* See if this is the smallest window so far. */
+			cwidth = e - s;
+			if (cwidth <= bwidth) {
+				if (cwidth == bwidth && ctotal <= btotal)
+					goto more;
+				bwidth = cwidth;
+				btotal = ctotal;
+				bs = s;
+			}
+more:
+			ctotal -= fs->fs_cs(fs, s).cs_nbfree;
+			s++;
+		}
+	}
+
+	/*
+	 * If we cannot allocate the minimum required or we use too many
+	 * extents to do so, return -1.
+	 */
+	if (btotal < minblk || bwidth > max_extents)
+		bs = -1;
+
+	return (bs);
+}

--- a/usr/src/uts/common/sys/fs/ufs_inode.h	Fri Jun 19 12:13:15 2009 -0600
+++ b/usr/src/uts/common/sys/fs/ufs_inode.h	Fri Jun 19 11:32:47 2009 -0700
@@ -878,7 +878,7 @@
 extern	int	ufs_freesp(struct vnode *, struct flock64 *, int, cred_t *);
 extern	ino_t	dirpref(inode_t *);
 extern	daddr_t	blkpref(struct inode *, daddr_t, int, daddr32_t *);
-extern	daddr_t	contigpref(ufsvfs_t *, size_t);
+extern	daddr_t	contigpref(ufsvfs_t *, size_t, size_t);
 
 extern	int	ufs_rdwri(enum uio_rw, int, struct inode *, caddr_t, ssize_t,
 	offset_t, enum uio_seg, int *, cred_t *);

--- a/usr/src/uts/common/sys/fs/ufs_log.h	Fri Jun 19 12:13:15 2009 -0600
+++ b/usr/src/uts/common/sys/fs/ufs_log.h	Fri Jun 19 11:32:47 2009 -0700
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
@@ -97,12 +97,25 @@
 #define	LDL_DIVISOR		1024 /* 1024 gives 1MB per 1GB */
 
 /*
+ * This gives the maximum size of log for which the 1MB per 1GB rule
+ * applies. The size of the log will only be greater than this based
+ * on the cylinder group space requirements.
+ */
+#define	LDL_SOFTLOGCAP		(256 * 1024 * 1024)
+
+/*
  * But set reasonable min/max units
- *   BUT never set LDL_MAXLOGSIZE to greater than LDL_REALMAXLOGSIZE.  The
- *   scan code will break (See sect_trailer).
  */
 #define	LDL_MINLOGSIZE		(1024 * 1024)
-#define	LDL_MAXLOGSIZE		(64 * 1024 * 1024)
+#define	LDL_MAXLOGSIZE		(512 * 1024 * 1024)
+
+/*
+ * Log space requirement per cylinder group. This needs to accommodate a
+ * cg delta (inc. header) and have a factor to cover other deltas involved
+ * in a single transaction which could touch all cyl groups in a file system.
+ */
+#define	LDL_CGSIZEREQ(fs) \
+	((fs)->fs_cgsize + ((fs)->fs_cgsize >> 1))
 
 #define	LDL_MINBUFSIZE		(32 * 1024)
 #define	LDL_USABLE_BSIZE	(DEV_BSIZE - sizeof (sect_trailer_t))