From: Fred Isaman <iisaman@xxxxxxxxxxxxxx>
Implements bl_write_begin and bl_do_flush, allowing block driver to read
in page "around" the data that is about to be copied to the page.
[pnfsblock: fix 64-bit compiler warnings for write_begin]
[pnfsblock: write_begin adjust for removed fields]
Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxxxxxx>
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
---
fs/nfs/blocklayout/blocklayout.c | 178 +++++++++++++++++++++++++++++++++++++-
1 files changed, 177 insertions(+), 1 deletions(-)
diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index d9bcb13..b9b961f 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -31,6 +31,8 @@
*/
#include <linux/module.h>
#include <linux/init.h>
+
+#include <linux/buffer_head.h> /* various write calls */
#include <linux/bio.h> /* struct bio */
#include <linux/vmalloc.h>
#include "blocklayout.h"
@@ -589,11 +591,185 @@ bl_clear_layoutdriver(struct nfs_server *server)
return 0;
}
+/* STUB - mark intersection of layout and page as bad, so is not
+ * used again.
+ */
+static void mark_bad_read(void)
+{
+ return;
+}
+
+/* Copied from buffer.c */
+static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
+{
+ if (uptodate) {
+ set_buffer_uptodate(bh);
+ } else {
+ /* This happens, due to failed READA attempts. */
+ clear_buffer_uptodate(bh);
+ }
+ unlock_buffer(bh);
+}
+
+/* Copied from buffer.c */
+static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
+{
+ __end_buffer_read_notouch(bh, uptodate);
+}
+
+/*
+ * map_block: map a requested I/0 block (isect) into an offset in the LVM
+ * meta block_device
+ */
+static void
+map_block(sector_t isect, struct pnfs_block_extent *be, struct buffer_head *bh)
+{
+ dprintk("%s enter be=%p\n", __func__, be);
+
+ set_buffer_mapped(bh);
+ bh->b_bdev = be->be_mdev;
+ bh->b_blocknr = (isect - be->be_f_offset + be->be_v_offset) >>
+ (be->be_mdev->bd_inode->i_blkbits - 9);
+
+ dprintk("%s isect %ld, bh->b_blocknr %ld, using bsize %Zd\n",
+ __func__, (long)isect,
+ (long)bh->b_blocknr,
+ bh->b_size);
+ return;
+}
+
+/* Given an unmapped page, zero it (or read in page for COW),
+ * and set appropriate flags/markings, but it is safe to not initialize
+ * the range given in [from, to).
+ */
+/* This is loosely based on nobh_write_begin */
+static int
+init_page_for_write(struct pnfs_block_layout *bl, struct page *page,
+ unsigned from, unsigned to, sector_t **pages_to_mark)
+{
+ struct buffer_head *bh;
+ int inval, ret = -EIO;
+ struct pnfs_block_extent *be = NULL, *cow_read = NULL;
+ sector_t isect;
+
+ dprintk("%s enter, %p\n", __func__, page);
+ bh = alloc_page_buffers(page, PAGE_CACHE_SIZE, 0);
+ if (!bh) {
+ ret = -ENOMEM;
+ goto cleanup;
+ }
+
+ isect = (sector_t)page->index << (PAGE_CACHE_SHIFT - 9);
+ be = find_get_extent(bl, isect, &cow_read);
+ if (!be)
+ goto cleanup;
+ inval = is_hole(be, isect);
+ dprintk("%s inval=%i, from=%u, to=%u\n", __func__, inval, from, to);
+ if (inval) {
+ if (be->be_state == PNFS_BLOCK_NONE_DATA) {
+ dprintk("%s PANIC - got NONE_DATA extent %p\n",
+ __func__, be);
+ goto cleanup;
+ }
+ map_block(isect, be, bh);
+ unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
+ }
+ if (PageUptodate(page)) {
+ /* Do nothing */
+ } else if (inval & !cow_read) {
+ zero_user_segments(page, 0, from, to, PAGE_CACHE_SIZE);
+ } else if (0 < from || PAGE_CACHE_SIZE > to) {
+ struct pnfs_block_extent *read_extent;
+
+ read_extent = (inval && cow_read) ? cow_read : be;
+ map_block(isect, read_extent, bh);
+ lock_buffer(bh);
+ bh->b_end_io = end_buffer_read_nobh;
+ submit_bh(READ, bh);
+ dprintk("%s: Waiting for buffer read\n", __func__);
+ /* XXX Don't really want to hold layout lock here */
+ wait_on_buffer(bh);
+ if (!buffer_uptodate(bh))
+ goto cleanup;
+ }
+ if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
+ /* There is a BUG here if is a short copy after write_begin,
+ * but I think this is a generic fs bug. The problem is that
+ * we have marked the page as initialized, but it is possible
+ * that the section not copied may never get copied.
+ */
+ ret = mark_initialized_sectors(be->be_inval, isect,
+ PAGE_CACHE_SECTORS,
+ pages_to_mark);
+ /* Want to preallocate mem so above can't fail */
+ if (ret)
+ goto cleanup;
+ }
+ SetPageMappedToDisk(page);
+ ret = 0;
+
+cleanup:
+ free_buffer_head(bh);
+ put_extent(be);
+ put_extent(cow_read);
+ if (ret) {
+ /* Need to mark layout with bad read...should now
+ * just use nfs4 for reads and writes.
+ */
+ mark_bad_read();
+ }
+ return ret;
+}
+
static int
bl_write_begin(struct pnfs_layout_segment *lseg, struct page *page, loff_t pos,
unsigned count, struct pnfs_fsdata *fsdata)
{
- return 0;
+ unsigned from, to;
+ int ret;
+ sector_t *pages_to_mark = NULL;
+ struct pnfs_block_layout *bl = BLK_LSEG2EXT(lseg);
+
+ dprintk("%s enter, %u@%lld\n", __func__, count, pos);
+ print_page(page);
+ /* The following code assumes blocksize >= PAGE_CACHE_SIZE */
+ if (bl->bl_blocksize < (PAGE_CACHE_SIZE >> 9)) {
+ dprintk("%s Can't handle blocksize %llu\n", __func__,
+ (u64)bl->bl_blocksize);
+ put_lseg(fsdata->lseg);
+ fsdata->lseg = NULL;
+ return 0;
+ }
+ if (PageMappedToDisk(page)) {
+ /* Basically, this is a flag that says we have
+ * successfully called write_begin already on this page.
+ */
+ /* NOTE - there are cache consistency issues here.
+ * For example, what if the layout is recalled, then regained?
+ * If the file is closed and reopened, will the page flags
+ * be reset? If not, we'll have to use layout info instead of
+ * the page flag.
+ */
+ return 0;
+ }
+ from = pos & (PAGE_CACHE_SIZE - 1);
+ to = from + count;
+ ret = init_page_for_write(bl, page, from, to, &pages_to_mark);
+ if (ret) {
+ dprintk("%s init page failed with %i", __func__, ret);
+ /* Revert back to plain NFS and just continue on with
+ * write. This assumes there is no request attached, which
+ * should be true if we get here.
+ */
+ BUG_ON(PagePrivate(page));
+ put_lseg(fsdata->lseg);
+ fsdata->lseg = NULL;
+ kfree(pages_to_mark);
+ ret = 0;
+ } else {
+ fsdata->private = pages_to_mark;
+ }
+ return ret;
}
static int
--
1.7.4.1
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