[GFS2] Fix unlinked file handling

This patch fixes the way we have been dealing with unlinked,
but still open files. It removes all limits (other than memory
for inodes, as per every other filesystem) on numbers of these
which we can support on GFS2. It also means that (like other
fs) its the responsibility of the last process to close the file
to deallocate the storage, rather than the person who did the
unlinking. Note that with GFS2, those two events might take place
on different nodes.

Also there are a number of other changes:

 o We use the Linux inode subsystem as it was intended to be
used, wrt allocating GFS2 inodes
 o The Linux inode cache is now the point which we use for
local enforcement of only holding one copy of the inode in
core at once (previous to this we used the glock layer).
 o We no longer use the unlinked "special" file. We just ignore it
completely. This makes unlinking more efficient.
 o We now use the 4th block allocation state. The previously unused
state is used to track unlinked but still open inodes.
 o gfs2_inoded is no longer needed
 o Several fields are now no longer needed (and removed) from the in
core struct gfs2_inode
 o Several fields are no longer needed (and removed) from the in core
superblock

There are a number of future possible optimisations and clean ups
which have been made possible by this patch.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 15 insertions, 16 deletions

diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 16d3ebd32092..207363aed112 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -81,7 +81,6 @@ int gfs2_get_block(struct inode *inode, sector_t lblock,
 static int get_block_noalloc(struct inode *inode, sector_t lblock,
 			     struct buffer_head *bh_result, int create)
 {
-	struct gfs2_inode *ip = inode->u.generic_ip;
 	int new = 0;
 	uint64_t dblock;
 	int error;
@@ -93,7 +92,7 @@ static int get_block_noalloc(struct inode *inode, sector_t lblock,
 
 	if (dblock)
 		map_bh(bh_result, inode->i_sb, dblock);
-	else if (gfs2_assert_withdraw(ip->i_sbd, !create))
+	else if (gfs2_assert_withdraw(GFS2_SB(inode), !create))
 		error = -EIO;
 	if (boundary)
 		set_buffer_boundary(bh_result);
@@ -114,8 +113,8 @@ static int get_block_noalloc(struct inode *inode, sector_t lblock,
 static int gfs2_writepage(struct page *page, struct writeback_control *wbc)
 {
 	struct inode *inode = page->mapping->host;
-	struct gfs2_inode *ip = page->mapping->host->u.generic_ip;
-	struct gfs2_sbd *sdp = ip->i_sbd;
+	struct gfs2_inode *ip = GFS2_I(page->mapping->host);
+	struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);
 	loff_t i_size = i_size_read(inode);
 	pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
 	unsigned offset;
@@ -216,8 +215,8 @@ static int stuffed_readpage(struct gfs2_inode *ip, struct page *page)
 
 static int gfs2_readpage(struct file *file, struct page *page)
 {
-	struct gfs2_inode *ip = page->mapping->host->u.generic_ip;
-	struct gfs2_sbd *sdp = ip->i_sbd;
+	struct gfs2_inode *ip = GFS2_I(page->mapping->host);
+	struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);
 	struct gfs2_holder gh;
 	int error;
 
@@ -271,8 +270,8 @@ static int gfs2_readpages(struct file *file, struct address_space *mapping,
 			  struct list_head *pages, unsigned nr_pages)
 {
 	struct inode *inode = mapping->host;
-	struct gfs2_inode *ip = inode->u.generic_ip;
-	struct gfs2_sbd *sdp = ip->i_sbd;
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct gfs2_holder gh;
 	unsigned page_idx;
 	int ret;
@@ -345,8 +344,8 @@ out_unlock:
 static int gfs2_prepare_write(struct file *file, struct page *page,
 			      unsigned from, unsigned to)
 {
-	struct gfs2_inode *ip = page->mapping->host->u.generic_ip;
-	struct gfs2_sbd *sdp = ip->i_sbd;
+	struct gfs2_inode *ip = GFS2_I(page->mapping->host);
+	struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);
 	unsigned int data_blocks, ind_blocks, rblocks;
 	int alloc_required;
 	int error = 0;
@@ -440,8 +439,8 @@ static int gfs2_commit_write(struct file *file, struct page *page,
 			     unsigned from, unsigned to)
 {
 	struct inode *inode = page->mapping->host;
-	struct gfs2_inode *ip = inode->u.generic_ip;
-	struct gfs2_sbd *sdp = ip->i_sbd;
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	int error = -EOPNOTSUPP;
 	struct buffer_head *dibh;
 	struct gfs2_alloc *al = &ip->i_alloc;;
@@ -520,7 +519,7 @@ fail_nounlock:
 
 static sector_t gfs2_bmap(struct address_space *mapping, sector_t lblock)
 {
-	struct gfs2_inode *ip = mapping->host->u.generic_ip;
+	struct gfs2_inode *ip = GFS2_I(mapping->host);
 	struct gfs2_holder i_gh;
 	sector_t dblock = 0;
 	int error;
@@ -594,7 +593,7 @@ static ssize_t gfs2_direct_IO_write(struct kiocb *iocb, const struct iovec *iov,
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
-	struct gfs2_inode *ip = inode->u.generic_ip;
+	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_holder gh;
 	int rv;
 
@@ -641,8 +640,8 @@ static ssize_t gfs2_direct_IO(int rw, struct kiocb *iocb,
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
-	struct gfs2_inode *ip = inode->u.generic_ip;
-	struct gfs2_sbd *sdp = ip->i_sbd;
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
 
 	if (rw == WRITE)
 		return gfs2_direct_IO_write(iocb, iov, offset, nr_segs);