[PATCH] Introduce SEEK_DATA/SEEK_HOLE support to XFS V1

[Jeff Liu <jeff.liu@oracle.com>]

Signed-off-by: Jie Liu <jeff.liu@oracle.com>

---
 fs/xfs/xfs_bmap.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_bmap.h |    1 +
 fs/xfs/xfs_file.c |   51 ++++++++++++++++++++++++++++++++-
 fs/xfs/xfs_iops.c |   64 +++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iops.h |    3 ++
 5 files changed, 199 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index c68baeb..04c3930 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -6133,3 +6133,84 @@ next_block:
 
 	return error;
 }
+
+
+int
+xfs_seek_data_hole(
+	struct xfs_inode	*ip,
+	loff_t			*start,
+	u32			type)
+{
+	xfs_mount_t		*mp = ip->i_mount;
+	xfs_fileoff_t		seekoff = *start;
+	xfs_fileoff_t		filelen;
+	xfs_extnum_t		lastx;
+	xfs_ifork_t		*ifp;
+	struct xfs_bmbt_irec	got;
+	struct xfs_bmbt_irec	prev;
+	u64			extoff;
+	u64			extlen;
+	int			eof;
+
+	if (xfs_get_extsz_hint(ip) ||
+	    ip->i_d.di_flags & (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)) {
+		filelen = XFS_MAXIOFFSET(mp);
+	} else {
+		filelen = ip->i_size;
+	}
+
+	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
+	xfs_bmap_search_extents(ip, XFS_BB_TO_FSBT(mp, BTOBB(*start)),
+				XFS_DATA_FORK, &eof, &lastx, &got, &prev);
+
+	if (type == SEEK_DATA) {
+		extoff = BBTOB(XFS_FSB_TO_BB(mp, got.br_startoff));
+		extlen = BBTOB(XFS_FSB_TO_BB(mp, got.br_blockcount));
+
+		if (eof) {
+			if (seekoff < extoff + extlen)
+				*start = seekoff;
+			else {
+				/*
+				 * There is no more data region past the
+				 * supplied offset.
+				 */
+				return XFS_ERROR(ENXIO);
+			}
+		}
+
+		*start = seekoff < extoff ? extoff : seekoff;
+	} else {
+		for (;;) {
+			extoff = BBTOB(XFS_FSB_TO_BB(mp, got.br_startoff));
+			extlen = BBTOB(XFS_FSB_TO_BB(mp, got.br_blockcount));
+			if (eof) {
+				/*
+				 * There might be a hole at the end of the
+				 * file, adjust to the file size.
+				 */
+				if (seekoff >= extoff) {
+					*start = min_t(xfs_fileoff_t, filelen,
+							(extoff + extlen));
+				}
+				break;
+			}
+
+			/* A hole found */
+			if (seekoff < extoff) {
+				*start = seekoff;
+				break;
+			}
+
+			/* Fetch the next extent */
+			seekoff = extoff + extlen;
+			if (++lastx < ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
+				xfs_bmbt_get_all(xfs_iext_get_ext(ifp, lastx),
+						 &got);
+			else
+				eof = 1;
+		}
+	}
+
+	return 0;
+}
diff --git a/fs/xfs/xfs_bmap.h b/fs/xfs/xfs_bmap.h
index 89ee672..964e29b 100644
--- a/fs/xfs/xfs_bmap.h
+++ b/fs/xfs/xfs_bmap.h
@@ -196,6 +196,7 @@ int	xfs_bunmapi(struct xfs_trans *tp, struct xfs_inode *ip,
 int	xfs_check_nostate_extents(struct xfs_ifork *ifp, xfs_extnum_t idx,
 		xfs_extnum_t num);
 uint	xfs_default_attroffset(struct xfs_inode *ip);
+int	xfs_seek_data_hole(struct xfs_inode *ip, loff_t *start, u32 type);
 
 #ifdef __KERNEL__
 /* bmap to userspace formatter - copy to user & advance pointer */
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 753ed9b..bf5471b 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1141,8 +1141,57 @@ xfs_vm_page_mkwrite(
 	return block_page_mkwrite(vma, vmf, xfs_get_blocks);
 }
 
+STATIC loff_t
+xfs_file_llseek(
+	struct file *file,
+	loff_t offset,
+	int origin)
+{
+	struct inode *inode = file->f_mapping->host;
+	int ret;
+
+	if (origin != SEEK_DATA && origin != SEEK_HOLE)
+		return generic_file_llseek(file, offset, origin);
+
+	mutex_lock(&inode->i_mutex);
+	switch (origin) {
+	case SEEK_DATA:
+	case SEEK_HOLE:
+		if (offset >= i_size_read(inode)) {
+			ret = -ENXIO;
+			goto error;
+		}
+
+		ret = xfs_find_desired_extent(inode, &offset, origin);
+		if (ret)
+			goto error;
+	}
+
+	if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	if (offset > inode->i_sb->s_maxbytes) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	if (offset != file->f_pos) {
+		file->f_pos = offset;
+		file->f_version = 0;
+	}
+
+	mutex_unlock(&inode->i_mutex);
+	return offset;
+
+error:
+	mutex_unlock(&inode->i_mutex);
+	return ret;
+}
+
 const struct file_operations xfs_file_operations = {
-	.llseek		= generic_file_llseek,
+	.llseek		= xfs_file_llseek,
 	.read		= do_sync_read,
 	.write		= do_sync_write,
 	.aio_read	= xfs_file_aio_read,
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 23ce927..482c1ff 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1030,6 +1030,70 @@ xfs_vn_fiemap(
 	return 0;
 }
 
+int
+xfs_find_desired_extent(
+	struct inode		*inode,
+	loff_t			*start,
+	u32			type)
+{
+	xfs_inode_t		*ip = XFS_I(inode);
+	xfs_mount_t		*mp = ip->i_mount;
+	struct xfs_ifork	*ifp;
+	int			lock;
+	int			error;
+
+	if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS &&
+	    ip->i_d.di_format != XFS_DINODE_FMT_BTREE &&
+	    ip->i_d.di_format != XFS_DINODE_FMT_LOCAL)
+		return XFS_ERROR(EINVAL);
+
+	xfs_ilock(ip, XFS_IOLOCK_SHARED);
+
+	/*
+	 * Flush the delay alloc blocks. Even after flushing the inode,
+	 * there can still be delalloc blocks on the inode beyond EOF
+	 * due to speculative preallocation. These are not removed until
+	 * the release function is called or the inode is inactivated.
+	 * Hence we cannot assert here that ip->i_delayed_blks == 0.
+	 */
+	if (ip->i_delayed_blks || ip->i_size > ip->i_d.di_size) {
+		error = xfs_flush_pages(ip, 0, -1, 0, FI_REMAPF);
+		if (error)
+			goto out_unlock_iolock;
+	}
+
+	lock = xfs_ilock_map_shared(ip);
+
+	if (XFS_FORCED_SHUTDOWN(mp)) {
+		error = EIO;
+		goto out_unlock_ilock;
+	}
+
+	XFS_STATS_INC(xs_blk_mapr);
+	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
+
+	ASSERT(ifp->if_ext_max ==
+	      XFS_IFORK_SIZE(ip, XFS_DATA_FORK) / (uint)sizeof(xfs_bmbt_rec_t));
+
+	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+		error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
+		if (error)
+			goto out_unlock_ilock;
+	}
+
+	error = xfs_seek_data_hole(ip, start, type);
+
+out_unlock_ilock:
+	xfs_iunlock_map_shared(ip, lock);
+out_unlock_iolock:
+	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+
+	if (error)
+		return -error;
+
+	return 0;
+}
+
 static const struct inode_operations xfs_inode_operations = {
 	.get_acl		= xfs_get_acl,
 	.getattr		= xfs_vn_getattr,
diff --git a/fs/xfs/xfs_iops.h b/fs/xfs/xfs_iops.h
index ef41c92..ea47abd 100644
--- a/fs/xfs/xfs_iops.h
+++ b/fs/xfs/xfs_iops.h
@@ -27,4 +27,7 @@ extern ssize_t xfs_vn_listxattr(struct dentry *, char *data, size_t size);
 
 extern void xfs_setup_inode(struct xfs_inode *);
 
+extern int xfs_find_desired_extent(struct inode *inode, loff_t *start,
+				   u32 type);
+
 #endif /* __XFS_IOPS_H__ */
-- 
1.7.4.1

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