[PATCH 18/18] xfs: allow writeback on pages without buffer heads

Christoph Hellwig
2018-05-30T10:01:33Z

Disable the IOMAP_F_BUFFER_HEAD flag on file systems with a block size
equal to the page size, and deal with pages without buffer heads in
writeback. Thanks to the previous refactoring this is basically trivial
now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/xfs_aops.c | 47 +++++++++++++++++++++++++++++++++-------------
fs/xfs/xfs_iomap.c | 3 ++-
2 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 84f88cecd2f1..6640377b6eae 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -91,6 +91,19 @@ xfs_find_daxdev_for_inode(
return mp->m_ddev_targp->bt_daxdev;
}

+static void
+xfs_finish_page_writeback(
+ struct inode *inode,
+ struct bio_vec *bvec,
+ int error)
+{
+ if (error) {
+ SetPageError(bvec->bv_page);
+ mapping_set_error(inode->i_mapping, -EIO);
+ }
+ end_page_writeback(bvec->bv_page);
+}
+
/*
* We're now finished for good with this page. Update the page state via the
* associated buffer_heads, paying attention to the start and end offsets that
@@ -103,7 +116,7 @@ xfs_find_daxdev_for_inode(
* and buffers potentially freed after every call to end_buffer_async_write.
*/
static void
-xfs_finish_page_writeback(
+xfs_finish_buffer_writeback(
struct inode *inode,
struct bio_vec *bvec,
int error)
@@ -178,9 +191,12 @@ xfs_destroy_ioend(
next = bio->bi_private;

/* walk each page on bio, ending page IO on them */
- bio_for_each_segment_all(bvec, bio, i)
- xfs_finish_page_writeback(inode, bvec, error);
-
+ bio_for_each_segment_all(bvec, bio, i) {
+ if (page_has_buffers(bvec->bv_page))
+ xfs_finish_buffer_writeback(inode, bvec, error);
+ else
+ xfs_finish_page_writeback(inode, bvec, error);
+ }
bio_put(bio);
}

@@ -782,13 +798,16 @@ xfs_writepage_map(
{
LIST_HEAD(submit_list);
struct xfs_ioend *ioend, *next;
- struct buffer_head *bh;
+ struct buffer_head *bh = NULL;
ssize_t len = i_blocksize(inode);
int error = 0;
int count = 0;
loff_t file_offset; /* file offset of page */
unsigned poffset; /* offset into page */

+ if (page_has_buffers(page))
+ bh = page_buffers(page);
+
/*
* Walk the blocks on the page, and we we run off then end of the
* current map or find the current map invalid, grab a new one.
@@ -797,11 +816,9 @@ xfs_writepage_map(
* replace the bufferhead with some other state tracking mechanism in
* future.
*/
- file_offset = page_offset(page);
- bh = page_buffers(page);
- for (poffset = 0;
+ for (poffset = 0, file_offset = page_offset(page);
poffset < PAGE_SIZE;
- poffset += len, file_offset += len, bh = bh->b_this_page) {
+ poffset += len, file_offset += len) {
/* past the range we are writing, so nothing more to write. */
if (file_offset >= end_offset)
break;
@@ -809,9 +826,10 @@ xfs_writepage_map(
/*
* Block does not contain valid data, skip it.
*/
- if (!buffer_uptodate(bh)) {
+ if (bh && !buffer_uptodate(bh)) {
if (PageUptodate(page))
ASSERT(buffer_mapped(bh));
+ bh = bh->b_this_page;
continue;
}

@@ -836,10 +854,15 @@ xfs_writepage_map(
* meaningless for holes (!mapped && uptodate), so check we did
* have a buffer covering a hole here and continue.
*/
+ if (bh)
+ bh = bh->b_this_page;
continue;
}

- xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
+ if (bh) {
+ xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
+ bh = bh->b_this_page;
+ }
xfs_add_to_ioend(inode, file_offset, page, wpc, wbc,
&submit_list);
count++;
@@ -939,8 +962,6 @@ xfs_do_writepage(

trace_xfs_writepage(inode, page, 0, 0);

- ASSERT(page_has_buffers(page));
-
/*
* Refuse to write the page out if we are called from reclaim context.
*
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index f949f0dd7382..93c40da3378a 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1031,7 +1031,8 @@ xfs_file_iomap_begin(
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;

- iomap->flags |= IOMAP_F_BUFFER_HEAD;
+ if (i_blocksize(inode) < PAGE_SIZE)
+ iomap->flags |= IOMAP_F_BUFFER_HEAD;

if (((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == IOMAP_WRITE) &&
!IS_DAX(inode) && !xfs_get_extsz_hint(ip)) {
--
2.17.0