[Fwd: [PATCH] Fix speculative allocation beyond eof]

[Lachlan McIlroy]

ping.

Anyone have any objections to this?

-------- Original Message --------
Subject: [PATCH] Fix speculative allocation beyond eof
Date: Tue, 23 Sep 2008 13:14:44 +1000
From: Lachlan McIlroy <lachlan at sgi.com>
Reply-To: lachlan at sgi.com
To: xfs-dev <xfs-dev at sgi.com>, xfs-oss <xfs at oss.sgi.com>

Speculative allocation beyond eof doesn't work properly.  It was broken some
time ago after a code cleanup that moved what is now xfs_iomap_eof_align_last_fsb()
and xfs_iomap_eof_want_preallocate() out of xfs_iomap_write_delay() into
separate functions.  The code used to use the current file size in various checks
but got changed to be max(file_size, i_new_size).  Since i_new_size is the result
of 'offset + count' then in xfs_iomap_eof_want_preallocate() the check for
'(offset + count) <= isize' will always be true.

ie if 'offset + count' is > ip->i_size then isize will be i_new_size and equal to
'offset + count'.

This change fixes all the places that used to use the current file size.

--- a/fs/xfs/xfs_iomap.c	2008-09-23 12:52:12.000000000 +1000
+++ b/fs/xfs/xfs_iomap.c	2008-09-23 12:51:29.000000000 +1000
@@ -290,7 +290,6 @@ STATIC int
xfs_iomap_eof_align_last_fsb(
	xfs_mount_t	*mp,
	xfs_inode_t	*ip,
-	xfs_fsize_t	isize,
	xfs_extlen_t	extsize,
	xfs_fileoff_t	*last_fsb)
{
@@ -306,14 +305,14 @@ xfs_iomap_eof_align_last_fsb(
	 * stripe width and we are allocating past the allocation eof.
	 */
	else if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC) &&
-	        (isize >= XFS_FSB_TO_B(mp, mp->m_swidth)))
+	        (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_swidth)))
		new_last_fsb = roundup_64(*last_fsb, mp->m_swidth);
	/*
	 * Roundup the allocation request to a stripe unit (m_dalign) boundary
	 * if the file size is >= stripe unit size, and we are allocating past
	 * the allocation eof.
	 */
-	else if (mp->m_dalign && (isize >= XFS_FSB_TO_B(mp, mp->m_dalign)))
+	else if (mp->m_dalign && (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_dalign)))
		new_last_fsb = roundup_64(*last_fsb, mp->m_dalign);

	/*
@@ -403,7 +402,6 @@ xfs_iomap_write_direct(
	xfs_filblks_t	count_fsb, resaligned;
	xfs_fsblock_t	firstfsb;
	xfs_extlen_t	extsz, temp;
-	xfs_fsize_t	isize;
	int		nimaps;
	int		bmapi_flag;
	int		quota_flag;
@@ -426,15 +424,10 @@ xfs_iomap_write_direct(
	rt = XFS_IS_REALTIME_INODE(ip);
	extsz = xfs_get_extsz_hint(ip);

-	isize = ip->i_size;
-	if (ip->i_new_size > isize)
-		isize = ip->i_new_size;
-
	offset_fsb = XFS_B_TO_FSBT(mp, offset);
	last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
-	if ((offset + count) > isize) {
-		error = xfs_iomap_eof_align_last_fsb(mp, ip, isize, extsz,
-							&last_fsb);
+	if ((offset + count) > ip->i_size) {
+		error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
		if (error)
			goto error_out;
	} else {
@@ -559,7 +552,6 @@ STATIC int
xfs_iomap_eof_want_preallocate(
	xfs_mount_t	*mp,
	xfs_inode_t	*ip,
-	xfs_fsize_t	isize,
	xfs_off_t	offset,
	size_t		count,
	int		ioflag,
@@ -573,7 +565,7 @@ xfs_iomap_eof_want_preallocate(
	int		n, error, imaps;

	*prealloc = 0;
-	if ((ioflag & BMAPI_SYNC) || (offset + count) <= isize)
+	if ((ioflag & BMAPI_SYNC) || (offset + count) <= ip->i_size)
		return 0;

	/*
@@ -617,7 +609,6 @@ xfs_iomap_write_delay(
	xfs_fileoff_t	ioalign;
	xfs_fsblock_t	firstblock;
	xfs_extlen_t	extsz;
-	xfs_fsize_t	isize;
	int		nimaps;
	xfs_bmbt_irec_t imap[XFS_WRITE_IMAPS];
	int		prealloc, fsynced = 0;
@@ -637,11 +628,7 @@ xfs_iomap_write_delay(
	offset_fsb = XFS_B_TO_FSBT(mp, offset);

retry:
-	isize = ip->i_size;
-	if (ip->i_new_size > isize)
-		isize = ip->i_new_size;
-
-	error = xfs_iomap_eof_want_preallocate(mp, ip, isize, offset, count,
+	error = xfs_iomap_eof_want_preallocate(mp, ip, offset, count,
				ioflag, imap, XFS_WRITE_IMAPS, &prealloc);
	if (error)
		return error;
@@ -655,8 +642,7 @@ retry:
	}

	if (prealloc || extsz) {
-		error = xfs_iomap_eof_align_last_fsb(mp, ip, isize, extsz,
-							&last_fsb);
+		error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
		if (error)
			return error;
	}