[PATCH 09/58] [GFS2] Add writepages for GFS2 jdata

swhiteho
2008-01-21T10:05:46Z

This patch resolves a lock ordering issue where we had been getting
a transaction lock in the wrong order with respect to the page lock.
By using writepages rather than just writepage, it is then possible
to start a transaction before locking the page, and thus matching the
locking order elsewhere in the code.

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

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 70b404d..1e1fe8d 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -650,7 +650,7 @@ static void gfs2_ordered_write(struct gfs2_sbd *sdp)
get_bh(bh);
gfs2_log_unlock(sdp);
lock_buffer(bh);
- if (test_clear_buffer_dirty(bh)) {
+ if (buffer_mapped(bh) && test_clear_buffer_dirty(bh)) {
bh->b_end_io = end_buffer_write_sync;
submit_bh(WRITE, bh);
} else {
diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 4bf73ed..48913e5 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -21,6 +21,7 @@
#include <linux/gfs2_ondisk.h>
#include <linux/lm_interface.h>
#include <linux/swap.h>
+#include <linux/pagevec.h>

#include "gfs2.h"
#include "incore.h"
@@ -189,6 +190,34 @@ static int gfs2_ordered_writepage(struct page *page,
}

/**
+ * __gfs2_jdata_writepage - The core of jdata writepage
+ * @page: The page to write
+ * @wbc: The writeback control
+ *
+ * This is shared between writepage and writepages and implements the
+ * core of the writepage operation. If a transaction is required then
+ * PageChecked will have been set and the transaction will have
+ * already been started before this is called.
+ */
+
+static int __gfs2_jdata_writepage(struct page *page, struct writeback_control *wbc)
+{
+ struct inode *inode = page->mapping->host;
+ struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_sbd *sdp = GFS2_SB(inode);
+
+ if (PageChecked(page)) {
+ ClearPageChecked(page);
+ if (!page_has_buffers(page)) {
+ create_empty_buffers(page, inode->i_sb->s_blocksize,
+ (1 << BH_Dirty)|(1 << BH_Uptodate));
+ }
+ gfs2_page_add_databufs(ip, page, 0, sdp->sd_vfs->s_blocksize-1);
+ }
+ return block_write_full_page(page, gfs2_get_block_noalloc, wbc);
+}
+
+/**
* gfs2_jdata_writepage - Write complete page
* @page: Page to write
*
@@ -199,7 +228,6 @@ static int gfs2_ordered_writepage(struct page *page,
static int gfs2_jdata_writepage(struct page *page, struct writeback_control *wbc)
{
struct inode *inode = page->mapping->host;
- struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_sbd *sdp = GFS2_SB(inode);
int error;
int done_trans = 0;
@@ -209,18 +237,14 @@ static int gfs2_jdata_writepage(struct page *page, struct writeback_control *wbc
return error;

if (PageChecked(page)) {
+ if (wbc->sync_mode != WB_SYNC_ALL)
+ goto out_ignore;
error = gfs2_trans_begin(sdp, RES_DINODE + 1, 0);
if (error)
goto out_ignore;
- ClearPageChecked(page);
- if (!page_has_buffers(page)) {
- create_empty_buffers(page, inode->i_sb->s_blocksize,
- (1 << BH_Dirty)|(1 << BH_Uptodate));
- }
- gfs2_page_add_databufs(ip, page, 0, sdp->sd_vfs->s_blocksize-1);
done_trans = 1;
}
- error = block_write_full_page(page, gfs2_get_block_noalloc, wbc);
+ error = __gfs2_jdata_writepage(page, wbc);
if (done_trans)
gfs2_trans_end(sdp);
return error;
@@ -247,6 +271,178 @@ static int gfs2_writeback_writepages(struct address_space *mapping,
}

/**
+ * gfs2_write_jdata_pagevec - Write back a pagevec's worth of pages
+ * @mapping: The mapping
+ * @wbc: The writeback control
+ * @writepage: The writepage function to call for each page
+ * @pvec: The vector of pages
+ * @nr_pages: The number of pages to write
+ *
+ * Returns: non-zero if loop should terminate, zero otherwise
+ */
+
+static int gfs2_write_jdata_pagevec(struct address_space *mapping,
+ struct writeback_control *wbc,
+ struct pagevec *pvec,
+ int nr_pages, pgoff_t end)
+{
+ struct inode *inode = mapping->host;
+ struct gfs2_sbd *sdp = GFS2_SB(inode);
+ loff_t i_size = i_size_read(inode);
+ pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
+ unsigned offset = i_size & (PAGE_CACHE_SIZE-1);
+ unsigned nrblocks = nr_pages * (PAGE_CACHE_SIZE/inode->i_sb->s_blocksize);
+ struct backing_dev_info *bdi = mapping->backing_dev_info;
+ int i;
+ int ret;
+
+ ret = gfs2_trans_begin(sdp, nrblocks, 0);
+ if (ret < 0)
+ return ret;
+
+ for(i = 0; i < nr_pages; i++) {
+ struct page *page = pvec->pages[i];
+
+ lock_page(page);
+
+ if (unlikely(page->mapping != mapping)) {
+ unlock_page(page);
+ continue;
+ }
+
+ if (!wbc->range_cyclic && page->index > end) {
+ ret = 1;
+ unlock_page(page);
+ continue;
+ }
+
+ if (wbc->sync_mode != WB_SYNC_NONE)
+ wait_on_page_writeback(page);
+
+ if (PageWriteback(page) ||
+ !clear_page_dirty_for_io(page)) {
+ unlock_page(page);
+ continue;
+ }
+
+ /* Is the page fully outside i_size? (truncate in progress) */
+ if (page->index > end_index || (page->index == end_index && !offset)) {
+ page->mapping->a_ops->invalidatepage(page, 0);
+ unlock_page(page);
+ continue;
+ }
+
+ ret = __gfs2_jdata_writepage(page, wbc);
+
+ if (ret || (--(wbc->nr_to_write) <= 0))
+ ret = 1;
+ if (wbc->nonblocking && bdi_write_congested(bdi)) {
+ wbc->encountered_congestion = 1;
+ ret = 1;
+ }
+
+ }
+ gfs2_trans_end(sdp);
+ return ret;
+}
+
+/**
+ * gfs2_write_cache_jdata - Like write_cache_pages but different
+ * @mapping: The mapping to write
+ * @wbc: The writeback control
+ * @writepage: The writepage function to call
+ * @data: The data to pass to writepage
+ *
+ * The reason that we use our own function here is that we need to
+ * start transactions before we grab page locks. This allows us
+ * to get the ordering right.
+ */
+
+static int gfs2_write_cache_jdata(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ struct backing_dev_info *bdi = mapping->backing_dev_info;
+ int ret = 0;
+ int done = 0;
+ struct pagevec pvec;
+ int nr_pages;
+ pgoff_t index;
+ pgoff_t end;
+ int scanned = 0;
+ int range_whole = 0;
+
+ if (wbc->nonblocking && bdi_write_congested(bdi)) {
+ wbc->encountered_congestion = 1;
+ return 0;
+ }
+
+ pagevec_init(&pvec, 0);
+ if (wbc->range_cyclic) {
+ index = mapping->writeback_index; /* Start from prev offset */
+ end = -1;
+ } else {
+ index = wbc->range_start >> PAGE_CACHE_SHIFT;
+ end = wbc->range_end >> PAGE_CACHE_SHIFT;
+ if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+ range_whole = 1;
+ scanned = 1;
+ }
+
+retry:
+ while (!done && (index <= end) &&
+ (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+ PAGECACHE_TAG_DIRTY,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
+ scanned = 1;
+ ret = gfs2_write_jdata_pagevec(mapping, wbc, &pvec, nr_pages, end);
+ if (ret)
+ done = 1;
+ if (ret > 0)
+ ret = 0;
+
+ pagevec_release(&pvec);
+ cond_resched();
+ }
+
+ if (!scanned && !done) {
+ /*
+ * We hit the last page and there is more work to be done: wrap
+ * back to the start of the file
+ */
+ scanned = 1;
+ index = 0;
+ goto retry;
+ }
+
+ if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
+ mapping->writeback_index = index;
+ return ret;
+}
+
+
+/**
+ * gfs2_jdata_writepages - Write a bunch of dirty pages back to disk
+ * @mapping: The mapping to write
+ * @wbc: The writeback control
+ *
+ */
+
+static int gfs2_jdata_writepages(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ struct gfs2_inode *ip = GFS2_I(mapping->host);
+ struct gfs2_sbd *sdp = GFS2_SB(mapping->host);
+ int ret;
+
+ ret = gfs2_write_cache_jdata(mapping, wbc);
+ if (ret == 0 && wbc->sync_mode == WB_SYNC_ALL) {
+ gfs2_log_flush(sdp, ip->i_gl);
+ ret = gfs2_write_cache_jdata(mapping, wbc);
+ }
+ return ret;
+}
+
+/**
* stuffed_readpage - Fill in a Linux page with stuffed file data
* @ip: the inode
* @page: the page
@@ -937,6 +1133,7 @@ static const struct address_space_operations gfs2_ordered_aops = {

static const struct address_space_operations gfs2_jdata_aops = {
.writepage = gfs2_jdata_writepage,
+ .writepages = gfs2_jdata_writepages,
.readpage = gfs2_readpage,
.readpages = gfs2_readpages,
.sync_page = block_sync_page,
--
1.5.1.2