[PATCH v5 7/9] iomap/xfs: Eliminate the iomap_valid handler

Andreas Gruenbacher
2022-12-31T15:11:41Z

Eliminate the ->iomap_valid() handler by switching to a ->get_folio()
handler and validating the mapping there.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/iomap/buffered-io.c | 25 +++++--------------------
fs/xfs/xfs_iomap.c | 37 ++++++++++++++++++++++++++-----------
include/linux/iomap.h | 22 +++++-----------------
3 files changed, 36 insertions(+), 48 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 4f363d42dbaf..df6fca11f18c 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -630,7 +630,7 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
const struct iomap *srcmap = iomap_iter_srcmap(iter);
struct folio *folio;
- int status = 0;
+ int status;

BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
if (srcmap != &iter->iomap)
@@ -646,27 +646,12 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
folio = page_ops->get_folio(iter, pos, len);
else
folio = iomap_get_folio(iter, pos);
- if (IS_ERR(folio))
- return PTR_ERR(folio);
-
- /*
- * Now we have a locked folio, before we do anything with it we need to
- * check that the iomap we have cached is not stale. The inode extent
- * mapping can change due to concurrent IO in flight (e.g.
- * IOMAP_UNWRITTEN state can change and memory reclaim could have
- * reclaimed a previously partially written page at this index after IO
- * completion before this write reaches this file offset) and hence we
- * could do the wrong thing here (zero a page range incorrectly or fail
- * to zero) and corrupt data.
- */
- if (page_ops && page_ops->iomap_valid) {
- bool iomap_valid = page_ops->iomap_valid(iter->inode,
- &iter->iomap);
- if (!iomap_valid) {
+ if (IS_ERR(folio)) {
+ if (folio == ERR_PTR(-ESTALE)) {
iter->iomap.flags |= IOMAP_F_STALE;
- status = 0;
- goto out_unlock;
+ return 0;
}
+ return PTR_ERR(folio);
}

if (pos + len > folio_pos(folio) + folio_size(folio))
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 669c1bc5c3a7..d0bf99539180 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -62,29 +62,44 @@ xfs_iomap_inode_sequence(
return cookie | READ_ONCE(ip->i_df.if_seq);
}

-/*
- * Check that the iomap passed to us is still valid for the given offset and
- * length.
- */
-static bool
-xfs_iomap_valid(
- struct inode *inode,
- const struct iomap *iomap)
+static struct folio *
+xfs_get_folio(
+ struct iomap_iter *iter,
+ loff_t pos,
+ unsigned len)
{
+ struct inode *inode = iter->inode;
+ struct iomap *iomap = &iter->iomap;
struct xfs_inode *ip = XFS_I(inode);
+ struct folio *folio;

+ folio = iomap_get_folio(iter, pos);
+ if (IS_ERR(folio))
+ return folio;
+
+ /*
+ * Now that we have a locked folio, we need to check that the iomap we
+ * have cached is not stale. The inode extent mapping can change due to
+ * concurrent IO in flight (e.g., IOMAP_UNWRITTEN state can change and
+ * memory reclaim could have reclaimed a previously partially written
+ * page at this index after IO completion before this write reaches
+ * this file offset) and hence we could do the wrong thing here (zero a
+ * page range incorrectly or fail to zero) and corrupt data.
+ */
if (iomap->validity_cookie !=
xfs_iomap_inode_sequence(ip, iomap->flags)) {
trace_xfs_iomap_invalid(ip, iomap);
- return false;
+ folio_unlock(folio);
+ folio_put(folio);
+ return ERR_PTR(-ESTALE);
}

XFS_ERRORTAG_DELAY(ip->i_mount, XFS_ERRTAG_WRITE_DELAY_MS);
- return true;
+ return folio;
}

const struct iomap_page_ops xfs_iomap_page_ops = {
- .iomap_valid = xfs_iomap_valid,
+ .get_folio = xfs_get_folio,
};

int
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index dd3575ada5d1..6f8e3321e475 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -134,29 +134,17 @@ static inline bool iomap_inline_data_valid(const struct iomap *iomap)
* When get_folio succeeds, put_folio will always be called to do any
* cleanup work necessary. put_folio is responsible for unlocking and putting
* @folio.
+ *
+ * When an iomap is created, the filesystem can store internal state (e.g., a
+ * sequence number) in iomap->validity_cookie. When it then detects in the
+ * get_folio handler that the iomap is no longer up to date and needs to be
+ * refreshed, it can return ERR_PTR(-ESTALE) to trigger a retry.
*/
struct iomap_page_ops {
struct folio *(*get_folio)(struct iomap_iter *iter, loff_t pos,
unsigned len);
void (*put_folio)(struct inode *inode, loff_t pos, unsigned copied,
struct folio *folio);
-
- /*
- * Check that the cached iomap still maps correctly to the filesystem's
- * internal extent map. FS internal extent maps can change while iomap
- * is iterating a cached iomap, so this hook allows iomap to detect that
- * the iomap needs to be refreshed during a long running write
- * operation.
- *
- * The filesystem can store internal state (e.g. a sequence number) in
- * iomap->validity_cookie when the iomap is first mapped to be able to
- * detect changes between mapping time and whenever .iomap_valid() is
- * called.
- *
- * This is called with the folio over the specified file position held
- * locked by the iomap code.
- */
- bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap);
};

/*
--
2.38.1