[GFS2] Use ->page_mkwrite() for mmap()
This cleans up the mmap() code path for GFS2 by implementing the
page_mkwrite function for GFS2. We are thus able to use the
generic filemap_fault function for our ->fault() implementation.
This now means that shared writable mappings will be much more
efficiently shared across the cluster if there is a reasonable
proportion of read activity (the greater proportion, the better).
As a side effect, it also reduces the size of the code, removes
special cases from readpage and readpages, and makes the code
path easier to follow.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/ops_file.c b/fs/gfs2/ops_file.c
index a729c86..6f3aeb0 100644
--- a/fs/gfs2/ops_file.c
+++ b/fs/gfs2/ops_file.c
@@ -33,7 +33,6 @@
#include "lm.h"
#include "log.h"
#include "meta_io.h"
-#include "ops_vm.h"
#include "quota.h"
#include "rgrp.h"
#include "trans.h"
@@ -169,7 +168,7 @@
if (put_user(fsflags, ptr))
error = -EFAULT;
- gfs2_glock_dq_m(1, &gh);
+ gfs2_glock_dq(&gh);
gfs2_holder_uninit(&gh);
return error;
}
@@ -293,6 +292,125 @@
return -ENOTTY;
}
+/**
+ * gfs2_allocate_page_backing - Use bmap to allocate blocks
+ * @page: The (locked) page to allocate backing for
+ *
+ * We try to allocate all the blocks required for the page in
+ * one go. This might fail for various reasons, so we keep
+ * trying until all the blocks to back this page are allocated.
+ * If some of the blocks are already allocated, thats ok too.
+ */
+
+static int gfs2_allocate_page_backing(struct page *page)
+{
+ struct inode *inode = page->mapping->host;
+ struct buffer_head bh;
+ unsigned long size = PAGE_CACHE_SIZE;
+ u64 lblock = page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+
+ do {
+ bh.b_state = 0;
+ bh.b_size = size;
+ gfs2_block_map(inode, lblock, 1, &bh);
+ if (!buffer_mapped(&bh))
+ return -EIO;
+ size -= bh.b_size;
+ lblock += (bh.b_size >> inode->i_blkbits);
+ } while(size > 0);
+ return 0;
+}
+
+/**
+ * gfs2_page_mkwrite - Make a shared, mmap()ed, page writable
+ * @vma: The virtual memory area
+ * @page: The page which is about to become writable
+ *
+ * When the page becomes writable, we need to ensure that we have
+ * blocks allocated on disk to back that page.
+ */
+
+static int gfs2_page_mkwrite(struct vm_area_struct *vma, struct page *page)
+{
+ struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
+ struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_sbd *sdp = GFS2_SB(inode);
+ unsigned long last_index;
+ u64 pos = page->index << (PAGE_CACHE_SIZE - inode->i_blkbits);
+ unsigned int data_blocks, ind_blocks, rblocks;
+ int alloc_required = 0;
+ struct gfs2_holder gh;
+ struct gfs2_alloc *al;
+ int ret;
+
+ gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_ATIME, &gh);
+ ret = gfs2_glock_nq_atime(&gh);
+ if (ret)
+ goto out;
+
+ set_bit(GIF_SW_PAGED, &ip->i_flags);
+ gfs2_write_calc_reserv(ip, PAGE_CACHE_SIZE, &data_blocks, &ind_blocks);
+ ret = gfs2_write_alloc_required(ip, pos, PAGE_CACHE_SIZE, &alloc_required);
+ if (ret || !alloc_required)
+ goto out_unlock;
+
+ ip->i_alloc.al_requested = 0;
+ al = gfs2_alloc_get(ip);
+ ret = gfs2_quota_lock(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
+ if (ret)
+ goto out_alloc_put;
+ ret = gfs2_quota_check(ip, ip->i_inode.i_uid, ip->i_inode.i_gid);
+ if (ret)
+ goto out_quota_unlock;
+ al->al_requested = data_blocks + ind_blocks;
+ ret = gfs2_inplace_reserve(ip);
+ if (ret)
+ goto out_quota_unlock;
+
+ rblocks = RES_DINODE + ind_blocks;
+ if (gfs2_is_jdata(ip))
+ rblocks += data_blocks ? data_blocks : 1;
+ if (ind_blocks || data_blocks)
+ rblocks += RES_STATFS + RES_QUOTA;
+ ret = gfs2_trans_begin(sdp, rblocks, 0);
+ if (ret)
+ goto out_trans_fail;
+
+ lock_page(page);
+ ret = -EINVAL;
+ last_index = ip->i_inode.i_size >> PAGE_CACHE_SHIFT;
+ if (page->index > last_index)
+ goto out_unlock_page;
+ if (!PageUptodate(page) || page->mapping != ip->i_inode.i_mapping)
+ goto out_unlock_page;
+ if (gfs2_is_stuffed(ip)) {
+ ret = gfs2_unstuff_dinode(ip, page);
+ if (ret)
+ goto out_unlock_page;
+ }
+ ret = gfs2_allocate_page_backing(page);
+
+out_unlock_page:
+ unlock_page(page);
+ gfs2_trans_end(sdp);
+out_trans_fail:
+ gfs2_inplace_release(ip);
+out_quota_unlock:
+ gfs2_quota_unlock(ip);
+out_alloc_put:
+ gfs2_alloc_put(ip);
+out_unlock:
+ gfs2_glock_dq(&gh);
+out:
+ gfs2_holder_uninit(&gh);
+ return ret;
+}
+
+static struct vm_operations_struct gfs2_vm_ops = {
+ .fault = filemap_fault,
+ .page_mkwrite = gfs2_page_mkwrite,
+};
+
/**
* gfs2_mmap -
@@ -315,14 +433,7 @@
return error;
}
- /* This is VM_MAYWRITE instead of VM_WRITE because a call
- to mprotect() can turn on VM_WRITE later. */
-
- if ((vma->vm_flags & (VM_MAYSHARE | VM_MAYWRITE)) ==
- (VM_MAYSHARE | VM_MAYWRITE))
- vma->vm_ops = &gfs2_vm_ops_sharewrite;
- else
- vma->vm_ops = &gfs2_vm_ops_private;
+ vma->vm_ops = &gfs2_vm_ops;
gfs2_glock_dq_uninit(&i_gh);
