[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, 26 insertions, 38 deletions

diff --git a/fs/gfs2/page.c b/fs/gfs2/page.c
index cd93644c7d70..a8165a693b56 100644
--- a/fs/gfs2/page.c
+++ b/fs/gfs2/page.c
@@ -38,20 +38,17 @@ void gfs2_pte_inval(struct gfs2_glock *gl)
         struct inode *inode;
 
         ip = gl->gl_object;
+        inode = &ip->i_inode;
         if (!ip || !S_ISREG(ip->i_di.di_mode))
                 return;
 
         if (!test_bit(GIF_PAGED, &ip->i_flags))
                 return;
 
-        inode = gfs2_ip2v_lookup(ip);
-        if (inode) {
-                unmap_shared_mapping_range(inode->i_mapping, 0, 0);
-                iput(inode);
+        unmap_shared_mapping_range(inode->i_mapping, 0, 0);
 
-                if (test_bit(GIF_SW_PAGED, &ip->i_flags))
-                        set_bit(GLF_DIRTY, &gl->gl_flags);
-        }
+        if (test_bit(GIF_SW_PAGED, &ip->i_flags))
+                set_bit(GLF_DIRTY, &gl->gl_flags);
 
         clear_bit(GIF_SW_PAGED, &ip->i_flags);
 }
@@ -68,19 +65,12 @@ void gfs2_page_inval(struct gfs2_glock *gl)
         struct inode *inode;
 
         ip = gl->gl_object;
+        inode = &ip->i_inode;
         if (!ip || !S_ISREG(ip->i_di.di_mode))
                 return;
 
-        inode = gfs2_ip2v_lookup(ip);
-        if (inode) {
-                struct address_space *mapping = inode->i_mapping;
-
-                truncate_inode_pages(mapping, 0);
-                gfs2_assert_withdraw(ip->i_sbd, !mapping->nrpages);
-
-                iput(inode);
-        }
-
+        truncate_inode_pages(inode->i_mapping, 0);
+        gfs2_assert_withdraw(GFS2_SB(&ip->i_inode), !inode->i_mapping->nrpages);
         clear_bit(GIF_PAGED, &ip->i_flags);
 }
 
@@ -97,32 +87,30 @@ void gfs2_page_sync(struct gfs2_glock *gl, int flags)
 {
         struct gfs2_inode *ip;
         struct inode *inode;
+        struct address_space *mapping;
+        int error = 0;
 
         ip = gl->gl_object;
+        inode = &ip->i_inode;
         if (!ip || !S_ISREG(ip->i_di.di_mode))
                 return;
 
-        inode = gfs2_ip2v_lookup(ip);
-        if (inode) {
-                struct address_space *mapping = inode->i_mapping;
-                int error = 0;
+        mapping = inode->i_mapping;
 
-                if (flags & DIO_START)
-                        filemap_fdatawrite(mapping);
-                if (!error && (flags & DIO_WAIT))
-                        error = filemap_fdatawait(mapping);
+        if (flags & DIO_START)
+                filemap_fdatawrite(mapping);
+        if (!error && (flags & DIO_WAIT))
+                error = filemap_fdatawait(mapping);
 
-                /* Put back any errors cleared by filemap_fdatawait()
-                   so they can be caught by someone who can pass them
-                   up to user space. */
+        /* Put back any errors cleared by filemap_fdatawait()
+           so they can be caught by someone who can pass them
+           up to user space. */
 
-                if (error == -ENOSPC)
-                        set_bit(AS_ENOSPC, &mapping->flags);
-                else if (error)
-                        set_bit(AS_EIO, &mapping->flags);
+        if (error == -ENOSPC)
+                set_bit(AS_ENOSPC, &mapping->flags);
+        else if (error)
+                set_bit(AS_EIO, &mapping->flags);
 
-                iput(inode);
-        }
 }
 
 /**
@@ -138,8 +126,8 @@ void gfs2_page_sync(struct gfs2_glock *gl, int flags)
 int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,
                         uint64_t block, void *private)
 {
-        struct gfs2_sbd *sdp = ip->i_sbd;
-        struct inode *inode = ip->i_vnode;
+        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+        struct inode *inode = &ip->i_inode;
         struct page *page = (struct page *)private;
         struct buffer_head *bh;
         int release = 0;
@@ -193,8 +181,8 @@ int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,
 int gfs2_block_truncate_page(struct address_space *mapping)
 {
         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);
         loff_t from = inode->i_size;
         unsigned long index = from >> PAGE_CACHE_SHIFT;
         unsigned offset = from & (PAGE_CACHE_SIZE-1);