On 10/29/20 9:33 AM, Brian Foster wrote:
iomap writeback mapping failure only calls into ->discard_page() if
the current page has not been added to the ioend. Accordingly, the
XFS callback assumes a full page discard and invalidation. This is
problematic for sub-page block size filesystems where some portion
of a page might have been mapped successfully before a failure to
map a delalloc block occurs. ->discard_page() is not called in that
error scenario and the bio is explicitly failed by iomap via the
error return from ->prepare_ioend(). As a result, the filesystem
leaks delalloc blocks and corrupts the filesystem block counters.
Since XFS is the only user of ->discard_page(), tweak the semantics
to invoke the callback unconditionally on mapping errors and provide
the file offset that failed to map. Update xfs_discard_page() to
discard the corresponding portion of the file and pass the range
along to iomap_invalidatepage(). The latter already properly handles
both full and sub-page scenarios by not changing any iomap or page
state on sub-page invalidations.
Looks ok to me
Reviewed-by: Allison Henderson <allison.henderson@xxxxxxxxxx>
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
v2.1:
- Rebased to v5.10-rc1.
fs/iomap/buffered-io.c | 15 ++++++++-------
fs/xfs/xfs_aops.c | 14 ++++++++------
include/linux/iomap.h | 2 +-
3 files changed, 17 insertions(+), 14 deletions(-)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 8180061b9e16..e4ea1f9f94d0 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1382,14 +1382,15 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
* appropriately.
*/
if (unlikely(error)) {
+ /*
+ * Let the filesystem know what portion of the current page
+ * failed to map. If the page wasn't been added to ioend, it
+ * won't be affected by I/O completion and we must unlock it
+ * now.
+ */
+ if (wpc->ops->discard_page)
+ wpc->ops->discard_page(page, file_offset);
if (!count) {
- /*
- * If the current page hasn't been added to ioend, it
- * won't be affected by I/O completions and we must
- * discard and unlock it right here.
- */
- if (wpc->ops->discard_page)
- wpc->ops->discard_page(page);
ClearPageUptodate(page);
unlock_page(page);
goto done;
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 55d126d4e096..5bf37afae5e9 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -527,13 +527,15 @@ xfs_prepare_ioend(
*/
static void
xfs_discard_page(
- struct page *page)
+ struct page *page,
+ loff_t fileoff)
{
struct inode *inode = page->mapping->host;
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
- loff_t offset = page_offset(page);
- xfs_fileoff_t start_fsb = XFS_B_TO_FSBT(mp, offset);
+ unsigned int pageoff = offset_in_page(fileoff);
+ xfs_fileoff_t start_fsb = XFS_B_TO_FSBT(mp, fileoff);
+ xfs_fileoff_t pageoff_fsb = XFS_B_TO_FSBT(mp, pageoff);
int error;
if (XFS_FORCED_SHUTDOWN(mp))
@@ -541,14 +543,14 @@ xfs_discard_page(
xfs_alert_ratelimited(mp,
"page discard on page "PTR_FMT", inode 0x%llx, offset %llu.",
- page, ip->i_ino, offset);
+ page, ip->i_ino, fileoff);
error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
- i_blocks_per_page(inode, page));
+ i_blocks_per_page(inode, page) - pageoff_fsb);
if (error && !XFS_FORCED_SHUTDOWN(mp))
xfs_alert(mp, "page discard unable to remove delalloc mapping.");
out_invalidate:
- iomap_invalidatepage(page, 0, PAGE_SIZE);
+ iomap_invalidatepage(page, pageoff, PAGE_SIZE - pageoff);
}
static const struct iomap_writeback_ops xfs_writeback_ops = {
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 172b3397a1a3..5bd3cac4df9c 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -221,7 +221,7 @@ struct iomap_writeback_ops {
* Optional, allows the file system to discard state on a page where
* we failed to submit any I/O.
*/
- void (*discard_page)(struct page *page);
+ void (*discard_page)(struct page *page, loff_t fileoff);
};
struct iomap_writepage_ctx {
