Merge tag 'xfs-6.2-merge-8' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull XFS updates from Darrick Wong:
 "The highlight of this is a batch of fixes for the online metadata
  checking code as we start the loooong march towards merging online
  repair. I aim to merge that in time for the 2023 LTS.

  There are also a large number of data corruption and race condition
  fixes in this patchset. Most notably fixed are write() calls to
  unwritten extents racing with writeback, which required some late(r
  than I prefer) code changes to iomap to support the necessary
  revalidations. I don't really like iomap changes going in past -rc4,
  but Dave and I have been working on it long enough that I chose to
  push it for 6.2 anyway.

  There are also a number of other subtle problems fixed, including the
  log racing with inode writeback to write inodes with incorrect link
  count to disk; file data mapping corruptions as a result of incorrect
  lock cycling when attaching dquots; refcount metadata corruption if
  one actually manages to share a block 2^32 times; and the log
  clobbering cow staging extents if they were formerly metadata blocks.

  Summary:

   - Fix a race condition w.r.t. percpu inode free counters

   - Fix a broken error return in xfs_remove

   - Print FS UUID at mount/unmount time

   - Numerous fixes to the online fsck code

   - Fix inode locking inconsistency problems when dealing with realtime
     metadata files

   - Actually merge pull requests so that we capture the cover letter
     contents

   - Fix a race between rebuilding VFS inode state and the AIL flushing
     inodes that could cause corrupt inodes to be written to the
     filesystem

   - Fix a data corruption problem resulting from a write() to an
     unwritten extent racing with writeback started on behalf of memory
     reclaim changing the extent state

   - Add debugging knobs so that we can test iomap invalidation

   - Fix the blockdev pagecache contents being stale after unmounting
     the filesystem, leading to spurious xfs_db errors and corrupt
     metadumps

   - Fix a file mapping corruption bug due to ilock cycling when
     attaching dquots to a file during delalloc reservation

   - Fix a refcount btree corruption problem due to the refcount
     adjustment code not handling MAXREFCOUNT correctly, resulting in
     unnecessary record splits

   - Fix COW staging extent alloctions not being classified as USERDATA,
     which results in filestreams being ignored and possible data
     corruption if the allocation was filled from the AGFL and the block
     buffer is still being tracked in the AIL

   - Fix new duplicated includes

   - Fix a race between the dquot shrinker and dquot freeing that could
     cause a UAF"

* tag 'xfs-6.2-merge-8' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (50 commits)
  xfs: dquot shrinker doesn't check for XFS_DQFLAG_FREEING
  xfs: Remove duplicated include in xfs_iomap.c
  xfs: invalidate xfs_bufs when allocating cow extents
  xfs: get rid of assert from xfs_btree_islastblock
  xfs: estimate post-merge refcounts correctly
  xfs: hoist refcount record merge predicates
  xfs: fix super block buf log item UAF during force shutdown
  xfs: wait iclog complete before tearing down AIL
  xfs: attach dquots to inode before reading data/cow fork mappings
  xfs: shut up -Wuninitialized in xfsaild_push
  xfs: use memcpy, not strncpy, to format the attr prefix during listxattr
  xfs: invalidate block device page cache during unmount
  xfs: add debug knob to slow down write for fun
  xfs: add debug knob to slow down writeback for fun
  xfs: drop write error injection is unfixable, remove it
  xfs: use iomap_valid method to detect stale cached iomaps
  iomap: write iomap validity checks
  xfs: xfs_bmap_punch_delalloc_range() should take a byte range
  iomap: buffered write failure should not truncate the page cache
  xfs,iomap: move delalloc punching to iomap
  ...

2 files changed, 271 insertions, 2 deletions

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 91ee0b308e13d..356193e44cf07 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -584,7 +584,7 @@ static int iomap_write_begin_inline(const struct iomap_iter *iter,
 	return iomap_read_inline_data(iter, folio);
 }
 
-static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
+static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
 		size_t len, struct folio **foliop)
 {
 	const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
@@ -618,6 +618,27 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 		status = (iter->flags & IOMAP_NOWAIT) ? -EAGAIN : -ENOMEM;
 		goto out_no_page;
 	}
+
+	/*
+	 * 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) {
+			iter->iomap.flags |= IOMAP_F_STALE;
+			status = 0;
+			goto out_unlock;
+		}
+	}
+
 	if (pos + len > folio_pos(folio) + folio_size(folio))
 		len = folio_pos(folio) + folio_size(folio) - pos;
 
@@ -773,6 +794,8 @@ again:
 		status = iomap_write_begin(iter, pos, bytes, &folio);
 		if (unlikely(status))
 			break;
+		if (iter->iomap.flags & IOMAP_F_STALE)
+			break;
 
 		page = folio_file_page(folio, pos >> PAGE_SHIFT);
 		if (mapping_writably_mapped(mapping))
@@ -832,6 +855,231 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
 }
 EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
 
+/*
+ * Scan the data range passed to us for dirty page cache folios. If we find a
+ * dirty folio, punch out the preceeding range and update the offset from which
+ * the next punch will start from.
+ *
+ * We can punch out storage reservations under clean pages because they either
+ * contain data that has been written back - in which case the delalloc punch
+ * over that range is a no-op - or they have been read faults in which case they
+ * contain zeroes and we can remove the delalloc backing range and any new
+ * writes to those pages will do the normal hole filling operation...
+ *
+ * This makes the logic simple: we only need to keep the delalloc extents only
+ * over the dirty ranges of the page cache.
+ *
+ * This function uses [start_byte, end_byte) intervals (i.e. open ended) to
+ * simplify range iterations.
+ */
+static int iomap_write_delalloc_scan(struct inode *inode,
+		loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte,
+		int (*punch)(struct inode *inode, loff_t offset, loff_t length))
+{
+	while (start_byte < end_byte) {
+		struct folio	*folio;
+
+		/* grab locked page */
+		folio = filemap_lock_folio(inode->i_mapping,
+				start_byte >> PAGE_SHIFT);
+		if (!folio) {
+			start_byte = ALIGN_DOWN(start_byte, PAGE_SIZE) +
+					PAGE_SIZE;
+			continue;
+		}
+
+		/* if dirty, punch up to offset */
+		if (folio_test_dirty(folio)) {
+			if (start_byte > *punch_start_byte) {
+				int	error;
+
+				error = punch(inode, *punch_start_byte,
+						start_byte - *punch_start_byte);
+				if (error) {
+					folio_unlock(folio);
+					folio_put(folio);
+					return error;
+				}
+			}
+
+			/*
+			 * Make sure the next punch start is correctly bound to
+			 * the end of this data range, not the end of the folio.
+			 */
+			*punch_start_byte = min_t(loff_t, end_byte,
+					folio_next_index(folio) << PAGE_SHIFT);
+		}
+
+		/* move offset to start of next folio in range */
+		start_byte = folio_next_index(folio) << PAGE_SHIFT;
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+	return 0;
+}
+
+/*
+ * Punch out all the delalloc blocks in the range given except for those that
+ * have dirty data still pending in the page cache - those are going to be
+ * written and so must still retain the delalloc backing for writeback.
+ *
+ * As we are scanning the page cache for data, we don't need to reimplement the
+ * wheel - mapping_seek_hole_data() does exactly what we need to identify the
+ * start and end of data ranges correctly even for sub-folio block sizes. This
+ * byte range based iteration is especially convenient because it means we
+ * don't have to care about variable size folios, nor where the start or end of
+ * the data range lies within a folio, if they lie within the same folio or even
+ * if there are multiple discontiguous data ranges within the folio.
+ *
+ * It should be noted that mapping_seek_hole_data() is not aware of EOF, and so
+ * can return data ranges that exist in the cache beyond EOF. e.g. a page fault
+ * spanning EOF will initialise the post-EOF data to zeroes and mark it up to
+ * date. A write page fault can then mark it dirty. If we then fail a write()
+ * beyond EOF into that up to date cached range, we allocate a delalloc block
+ * beyond EOF and then have to punch it out. Because the range is up to date,
+ * mapping_seek_hole_data() will return it, and we will skip the punch because
+ * the folio is dirty. THis is incorrect - we always need to punch out delalloc
+ * beyond EOF in this case as writeback will never write back and covert that
+ * delalloc block beyond EOF. Hence we limit the cached data scan range to EOF,
+ * resulting in always punching out the range from the EOF to the end of the
+ * range the iomap spans.
+ *
+ * Intervals are of the form [start_byte, end_byte) (i.e. open ended) because it
+ * matches the intervals returned by mapping_seek_hole_data(). i.e. SEEK_DATA
+ * returns the start of a data range (start_byte), and SEEK_HOLE(start_byte)
+ * returns the end of the data range (data_end). Using closed intervals would
+ * require sprinkling this code with magic "+ 1" and "- 1" arithmetic and expose
+ * the code to subtle off-by-one bugs....
+ */
+static int iomap_write_delalloc_release(struct inode *inode,
+		loff_t start_byte, loff_t end_byte,
+		int (*punch)(struct inode *inode, loff_t pos, loff_t length))
+{
+	loff_t punch_start_byte = start_byte;
+	loff_t scan_end_byte = min(i_size_read(inode), end_byte);
+	int error = 0;
+
+	/*
+	 * Lock the mapping to avoid races with page faults re-instantiating
+	 * folios and dirtying them via ->page_mkwrite whilst we walk the
+	 * cache and perform delalloc extent removal. Failing to do this can
+	 * leave dirty pages with no space reservation in the cache.
+	 */
+	filemap_invalidate_lock(inode->i_mapping);
+	while (start_byte < scan_end_byte) {
+		loff_t		data_end;
+
+		start_byte = mapping_seek_hole_data(inode->i_mapping,
+				start_byte, scan_end_byte, SEEK_DATA);
+		/*
+		 * If there is no more data to scan, all that is left is to
+		 * punch out the remaining range.
+		 */
+		if (start_byte == -ENXIO || start_byte == scan_end_byte)
+			break;
+		if (start_byte < 0) {
+			error = start_byte;
+			goto out_unlock;
+		}
+		WARN_ON_ONCE(start_byte < punch_start_byte);
+		WARN_ON_ONCE(start_byte > scan_end_byte);
+
+		/*
+		 * We find the end of this contiguous cached data range by
+		 * seeking from start_byte to the beginning of the next hole.
+		 */
+		data_end = mapping_seek_hole_data(inode->i_mapping, start_byte,
+				scan_end_byte, SEEK_HOLE);
+		if (data_end < 0) {
+			error = data_end;
+			goto out_unlock;
+		}
+		WARN_ON_ONCE(data_end <= start_byte);
+		WARN_ON_ONCE(data_end > scan_end_byte);
+
+		error = iomap_write_delalloc_scan(inode, &punch_start_byte,
+				start_byte, data_end, punch);
+		if (error)
+			goto out_unlock;
+
+		/* The next data search starts at the end of this one. */
+		start_byte = data_end;
+	}
+
+	if (punch_start_byte < end_byte)
+		error = punch(inode, punch_start_byte,
+				end_byte - punch_start_byte);
+out_unlock:
+	filemap_invalidate_unlock(inode->i_mapping);
+	return error;
+}
+
+/*
+ * When a short write occurs, the filesystem may need to remove reserved space
+ * that was allocated in ->iomap_begin from it's ->iomap_end method. For
+ * filesystems that use delayed allocation, we need to punch out delalloc
+ * extents from the range that are not dirty in the page cache. As the write can
+ * race with page faults, there can be dirty pages over the delalloc extent
+ * outside the range of a short write but still within the delalloc extent
+ * allocated for this iomap.
+ *
+ * This function uses [start_byte, end_byte) intervals (i.e. open ended) to
+ * simplify range iterations.
+ *
+ * The punch() callback *must* only punch delalloc extents in the range passed
+ * to it. It must skip over all other types of extents in the range and leave
+ * them completely unchanged. It must do this punch atomically with respect to
+ * other extent modifications.
+ *
+ * The punch() callback may be called with a folio locked to prevent writeback
+ * extent allocation racing at the edge of the range we are currently punching.
+ * The locked folio may or may not cover the range being punched, so it is not
+ * safe for the punch() callback to lock folios itself.
+ *
+ * Lock order is:
+ *
+ * inode->i_rwsem (shared or exclusive)
+ *   inode->i_mapping->invalidate_lock (exclusive)
+ *     folio_lock()
+ *       ->punch
+ *         internal filesystem allocation lock
+ */
+int iomap_file_buffered_write_punch_delalloc(struct inode *inode,
+		struct iomap *iomap, loff_t pos, loff_t length,
+		ssize_t written,
+		int (*punch)(struct inode *inode, loff_t pos, loff_t length))
+{
+	loff_t			start_byte;
+	loff_t			end_byte;
+	int			blocksize = i_blocksize(inode);
+
+	if (iomap->type != IOMAP_DELALLOC)
+		return 0;
+
+	/* If we didn't reserve the blocks, we're not allowed to punch them. */
+	if (!(iomap->flags & IOMAP_F_NEW))
+		return 0;
+
+	/*
+	 * start_byte refers to the first unused block after a short write. If
+	 * nothing was written, round offset down to point at the first block in
+	 * the range.
+	 */
+	if (unlikely(!written))
+		start_byte = round_down(pos, blocksize);
+	else
+		start_byte = round_up(pos + written, blocksize);
+	end_byte = round_up(pos + length, blocksize);
+
+	/* Nothing to do if we've written the entire delalloc extent */
+	if (start_byte >= end_byte)
+		return 0;
+
+	return iomap_write_delalloc_release(inode, start_byte, end_byte,
+					punch);
+}
+EXPORT_SYMBOL_GPL(iomap_file_buffered_write_punch_delalloc);
+
 static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 {
 	struct iomap *iomap = &iter->iomap;
@@ -856,6 +1104,8 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 		status = iomap_write_begin(iter, pos, bytes, &folio);
 		if (unlikely(status))
 			return status;
+		if (iter->iomap.flags & IOMAP_F_STALE)
+			break;
 
 		status = iomap_write_end(iter, pos, bytes, bytes, folio);
 		if (WARN_ON_ONCE(status == 0))
@@ -911,6 +1161,8 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 		status = iomap_write_begin(iter, pos, bytes, &folio);
 		if (status)
 			return status;
+		if (iter->iomap.flags & IOMAP_F_STALE)
+			break;
 
 		offset = offset_in_folio(folio, pos);
 		if (bytes > folio_size(folio) - offset)
diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c
index a1c7592d2aded..79a0614eaab77 100644
--- a/fs/iomap/iter.c
+++ b/fs/iomap/iter.c
@@ -7,12 +7,28 @@
 #include <linux/iomap.h>
 #include "trace.h"
 
+/*
+ * Advance to the next range we need to map.
+ *
+ * If the iomap is marked IOMAP_F_STALE, it means the existing map was not fully
+ * processed - it was aborted because the extent the iomap spanned may have been
+ * changed during the operation. In this case, the iteration behaviour is to
+ * remap the unprocessed range of the iter, and that means we may need to remap
+ * even when we've made no progress (i.e. iter->processed = 0). Hence the
+ * "finished iterating" case needs to distinguish between
+ * (processed = 0) meaning we are done and (processed = 0 && stale) meaning we
+ * need to remap the entire remaining range.
+ */
 static inline int iomap_iter_advance(struct iomap_iter *iter)
 {
+	bool stale = iter->iomap.flags & IOMAP_F_STALE;
+
 	/* handle the previous iteration (if any) */
 	if (iter->iomap.length) {
-		if (iter->processed <= 0)
+		if (iter->processed < 0)
 			return iter->processed;
+		if (!iter->processed && !stale)
+			return 0;
 		if (WARN_ON_ONCE(iter->processed > iomap_length(iter)))
 			return -EIO;
 		iter->pos += iter->processed;
@@ -33,6 +49,7 @@ static inline void iomap_iter_done(struct iomap_iter *iter)
 	WARN_ON_ONCE(iter->iomap.offset > iter->pos);
 	WARN_ON_ONCE(iter->iomap.length == 0);
 	WARN_ON_ONCE(iter->iomap.offset + iter->iomap.length <= iter->pos);
+	WARN_ON_ONCE(iter->iomap.flags & IOMAP_F_STALE);
 
 	trace_iomap_iter_dstmap(iter->inode, &iter->iomap);
 	if (iter->srcmap.type != IOMAP_HOLE)