[PATCH 1/8] Revert "ext4: remove no longer used functions in inode.c"

[PATCH 1/8] Revert "ext4: remove no longer used functions in inode.c"

[Lukas Czerner]

This reverts commit ccb4d7af914e0fe9b2f1022f8ea6c300463fd5e6.

This commit reintroduces functions ext4_block_truncate_page() and
ext4_block_zero_page_range() which has been previously removed in favour
of ext4_discard_partial_page_buffers().

In future commits we want to reintroduce those function and remove
ext4_discard_partial_page_buffers() since it is duplicating some code
and also partially duplicating work of truncate_pagecache_range(),
moreover the old implementation was much clearer.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 fs/ext4/ext4.h  |    4 ++
 fs/ext4/inode.c |  120 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 124 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index cfc4e01..439af1e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1995,6 +1995,10 @@ extern int ext4_alloc_da_blocks(struct inode *inode);
 extern void ext4_set_aops(struct inode *inode);
 extern int ext4_writepage_trans_blocks(struct inode *);
 extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
+extern int ext4_block_truncate_page(handle_t *handle,
+		struct address_space *mapping, loff_t from);
+extern int ext4_block_zero_page_range(handle_t *handle,
+		struct address_space *mapping, loff_t from, loff_t length);
 extern int ext4_discard_partial_page_buffers(handle_t *handle,
 		struct address_space *mapping, loff_t from,
 		loff_t length, int flags);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 02bc8cb..588f9fa 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3381,6 +3381,126 @@ next:
 	return err;
 }
 
+/*
+ * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
+ * up to the end of the block which corresponds to `from'.
+ * This required during truncate. We need to physically zero the tail end
+ * of that block so it doesn't yield old data if the file is later grown.
+ */
+int ext4_block_truncate_page(handle_t *handle,
+		struct address_space *mapping, loff_t from)
+{
+	unsigned offset = from & (PAGE_CACHE_SIZE-1);
+	unsigned length;
+	unsigned blocksize;
+	struct inode *inode = mapping->host;
+
+	blocksize = inode->i_sb->s_blocksize;
+	length = blocksize - (offset & (blocksize - 1));
+
+	return ext4_block_zero_page_range(handle, mapping, from, length);
+}
+
+/*
+ * ext4_block_zero_page_range() zeros out a mapping of length 'length'
+ * starting from file offset 'from'.  The range to be zero'd must
+ * be contained with in one block.  If the specified range exceeds
+ * the end of the block it will be shortened to end of the block
+ * that cooresponds to 'from'
+ */
+int ext4_block_zero_page_range(handle_t *handle,
+		struct address_space *mapping, loff_t from, loff_t length)
+{
+	ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT;
+	unsigned offset = from & (PAGE_CACHE_SIZE-1);
+	unsigned blocksize, max, pos;
+	ext4_lblk_t iblock;
+	struct inode *inode = mapping->host;
+	struct buffer_head *bh;
+	struct page *page;
+	int err = 0;
+
+	page = find_or_create_page(mapping, from >> PAGE_CACHE_SHIFT,
+				   mapping_gfp_mask(mapping) & ~__GFP_FS);
+	if (!page)
+		return -ENOMEM;
+
+	blocksize = inode->i_sb->s_blocksize;
+	max = blocksize - (offset & (blocksize - 1));
+
+	/*
+	 * correct length if it does not fall between
+	 * 'from' and the end of the block
+	 */
+	if (length > max || length < 0)
+		length = max;
+
+	iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, blocksize, 0);
+
+	/* Find the buffer that contains "offset" */
+	bh = page_buffers(page);
+	pos = blocksize;
+	while (offset >= pos) {
+		bh = bh->b_this_page;
+		iblock++;
+		pos += blocksize;
+	}
+
+	err = 0;
+	if (buffer_freed(bh)) {
+		BUFFER_TRACE(bh, "freed: skip");
+		goto unlock;
+	}
+
+	if (!buffer_mapped(bh)) {
+		BUFFER_TRACE(bh, "unmapped");
+		ext4_get_block(inode, iblock, bh, 0);
+		/* unmapped? It's a hole - nothing to do */
+		if (!buffer_mapped(bh)) {
+			BUFFER_TRACE(bh, "still unmapped");
+			goto unlock;
+		}
+	}
+
+	/* Ok, it's mapped. Make sure it's up-to-date */
+	if (PageUptodate(page))
+		set_buffer_uptodate(bh);
+
+	if (!buffer_uptodate(bh)) {
+		err = -EIO;
+		ll_rw_block(READ, 1, &bh);
+		wait_on_buffer(bh);
+		/* Uhhuh. Read error. Complain and punt. */
+		if (!buffer_uptodate(bh))
+			goto unlock;
+	}
+
+	if (ext4_should_journal_data(inode)) {
+		BUFFER_TRACE(bh, "get write access");
+		err = ext4_journal_get_write_access(handle, bh);
+		if (err)
+			goto unlock;
+	}
+
+	zero_user(page, offset, length);
+
+	BUFFER_TRACE(bh, "zeroed end of block");
+
+	err = 0;
+	if (ext4_should_journal_data(inode)) {
+		err = ext4_handle_dirty_metadata(handle, inode, bh);
+	} else
+		mark_buffer_dirty(bh);
+
+unlock:
+	unlock_page(page);
+	page_cache_release(page);
+	return err;
+}
+
 int ext4_can_truncate(struct inode *inode)
 {
 	if (S_ISREG(inode->i_mode))
-- 
1.7.7.6

[PATCH 2/8] Revert "ext4: fix fsx truncate failure"

[Lukas Czerner]

This reverts commit 189e868fa8fdca702eb9db9d8afc46b5cb9144c9.

This commit reintroduces the use of ext4_block_truncate_page() in ext4
truncate operation instead of ext4_discard_partial_page_buffers().

The statement in the commit description that the truncate operation only
zero block unaligned portion of the last page is not exactly right,
since truncate_pagecache_range() also zeroes and invalidate the unaligned
portion of the page. Then there is no need to zero and unmap it once more
and ext4_block_truncate_page() was doing the right job, although we
still need to update the buffer head containing the last block, which is
exactly what ext4_block_truncate_page() is doing.

This was tested on ppc64 machine with block size of 1024 bytes without
any problems.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 fs/ext4/extents.c  |   13 ++-----------
 fs/ext4/indirect.c |   13 ++-----------
 2 files changed, 4 insertions(+), 22 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 91341ec..ceab5f5 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4222,7 +4222,6 @@ void ext4_ext_truncate(struct inode *inode)
 	struct super_block *sb = inode->i_sb;
 	ext4_lblk_t last_block;
 	handle_t *handle;
-	loff_t page_len;
 	int err = 0;
 
 	/*
@@ -4239,16 +4238,8 @@ void ext4_ext_truncate(struct inode *inode)
 	if (IS_ERR(handle))
 		return;
 
-	if (inode->i_size % PAGE_CACHE_SIZE != 0) {
-		page_len = PAGE_CACHE_SIZE -
-			(inode->i_size & (PAGE_CACHE_SIZE - 1));
-
-		err = ext4_discard_partial_page_buffers(handle,
-			mapping, inode->i_size, page_len, 0);
-
-		if (err)
-			goto out_stop;
-	}
+	if (inode->i_size & (sb->s_blocksize - 1))
+		ext4_block_truncate_page(handle, mapping, inode->i_size);
 
 	if (ext4_orphan_add(handle, inode))
 		goto out_stop;
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 830e1b2..a082b30 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -1349,9 +1349,7 @@ void ext4_ind_truncate(struct inode *inode)
 	__le32 nr = 0;
 	int n = 0;
 	ext4_lblk_t last_block, max_block;
-	loff_t page_len;
 	unsigned blocksize = inode->i_sb->s_blocksize;
-	int err;
 
 	handle = start_transaction(inode);
 	if (IS_ERR(handle))
@@ -1362,16 +1360,9 @@ void ext4_ind_truncate(struct inode *inode)
 	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
 					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
 
-	if (inode->i_size % PAGE_CACHE_SIZE != 0) {
-		page_len = PAGE_CACHE_SIZE -
-			(inode->i_size & (PAGE_CACHE_SIZE - 1));
-
-		err = ext4_discard_partial_page_buffers(handle,
-			mapping, inode->i_size, page_len, 0);

[PATCH 3/8] shmem: pass LLONG_MAX to shmem_truncate_range

[Lukas Czerner]

Currently we're passing -1 to shmem_truncate_range which can then call
truncate_inode_pages_range() which is actually really confusing since the
argument is signed so we do not get "huge" number as one would expect,
but rather just -1. To make things clearer and easier for
truncate_inode_pages_range() just pass LLONG_MAX since it is actually what
was intended anyway.

It also makes thing easier for allowing truncate_inode_pages_range() to
handle non page aligned regions. Moreover letting the lend argument to
be negative might actually hide some bugs.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
---
 mm/shmem.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index a15a466..470ee75 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2960,7 +2960,8 @@ void shmem_unlock_mapping(struct address_space *mapping)
 
 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 {
-	truncate_inode_pages_range(inode->i_mapping, lstart, lend);
+	truncate_inode_pages_range(inode->i_mapping, lstart,
+				   lend == -1 ? LLONG_MAX : last);
 }
 EXPORT_SYMBOL_GPL(shmem_truncate_range);
 
-- 
1.7.7.6

[PATCH 4/8] xfs: pass LLONG_MAX to truncate_inode_pages_range

[Lukas Czerner]

Currently we're passing -1 to truncate_inode_pages_range() which is
actually really confusing since the argument is signed so we do not get
"huge" number as one would expect, but rather just -1. To make things
clearer and easier for truncate_inode_pages_range() just pass LLONG_MAX
since it is actually what was intended anyway.

It also makes thing easier for allowing truncate_inode_pages_range() to
handle non page aligned regions. Moreover letting the lend argument to
be negative might actually hide some bugs.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_fs_subr.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_fs_subr.c b/fs/xfs/xfs_fs_subr.c
index 652b875..6e9b052 100644
--- a/fs/xfs/xfs_fs_subr.c
+++ b/fs/xfs/xfs_fs_subr.c
@@ -34,7 +34,8 @@ xfs_tosspages(
 {
 	/* can't toss partial tail pages, so mask them out */
 	last &= ~(PAGE_SIZE - 1);
-	truncate_inode_pages_range(VFS_I(ip)->i_mapping, first, last - 1);
+	truncate_inode_pages_range(VFS_I(ip)->i_mapping, first,
+				   last == -1 ? LLONG_MAX : last);
 }
 
 int
@@ -53,7 +54,8 @@ xfs_flushinval_pages(
 	ret = filemap_write_and_wait_range(mapping, first,
 				last == -1 ? LLONG_MAX : last);
 	if (!ret)
-		truncate_inode_pages_range(mapping, first, last);
+		truncate_inode_pages_range(mapping, first,
+					   last == -1 ? LLONG_MAX : last);
 	return -ret;
 }
 
-- 
1.7.7.6

[PATCH 5/8] mm: pass LLONG_MAX to truncate_inode_pages_range

[Lukas Czerner]

Currently we're passing -1 to truncate_inode_pages_range() which is
actually really confusing since the argument is signed so we do not get
"huge" number as one would expect, but rather just -1. To make things
clearer and easier for truncate_inode_pages_range() just pass LLONG_MAX
since it is actually what was intended anyway.

It also makes thing easier for allowing truncate_inode_pages_range() to
handle non page aligned regions. Moreover letting the lend argument to
be negative might actually hide some bugs.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
---
 mm/truncate.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index 75801ac..77a693e 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -310,7 +310,7 @@ EXPORT_SYMBOL(truncate_inode_pages_range);
  */
 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
 {
-	truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
+	truncate_inode_pages_range(mapping, lstart, (loff_t)LLONG_MAX);
 }
 EXPORT_SYMBOL(truncate_inode_pages);
 
-- 
1.7.7.6

[PATCH 6/8] mm: teach truncate_inode_pages_range() to hadnle non page aligned ranges

[Lukas Czerner]

This commit changes truncate_inode_pages_range() so it can handle non
page aligned regions of the truncate. Currently we can hit BUG_ON when
the end of the range is not page aligned, but he can handle unaligned
start of the range.

Being able to handle non page aligned regions of the page can help file
system punch_hole implementations and save some work, because once we're
holding the page we might as well deal with it right away.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
---
 mm/truncate.c |   61 ++++++++++++++++++++++++++++++++++++++++++++++----------
 1 files changed, 50 insertions(+), 11 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index 77a693e..92aa4ad 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -49,6 +49,16 @@ void do_invalidatepage(struct page *page, unsigned long offset)
 		(*invalidatepage)(page, offset);
 }
 
+static inline void punch_hole_into_page(struct page *page, unsigned start,
+					unsigned end)
+{
+	BUG_ON(end > PAGE_CACHE_SIZE);
+	zero_user_segment(page, start, end);
+	cleancache_invalidate_page(page->mapping, page);
+	if (page_has_private(page))
+		do_invalidatepage(page, start);
+}
+
 static inline void truncate_partial_page(struct page *page, unsigned partial)
 {
 	zero_user_segment(page, partial, PAGE_CACHE_SIZE);
@@ -206,24 +216,30 @@ int invalidate_inode_page(struct page *page)
 void truncate_inode_pages_range(struct address_space *mapping,
 				loff_t lstart, loff_t lend)
 {
-	const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
-	const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
+	const unsigned partial_start = lstart & (PAGE_CACHE_SIZE - 1);
+	const unsigned partial_end = lend & (PAGE_CACHE_SIZE - 1);
+	loff_t start = lstart >> PAGE_CACHE_SHIFT;
+	loff_t end = lend >> PAGE_CACHE_SHIFT;
 	struct pagevec pvec;
-	pgoff_t index;
-	pgoff_t end;
+	loff_t index;
 	int i;
 
+	BUG_ON(lend < start || lend < 0);
+
 	cleancache_invalidate_inode(mapping);
 	if (mapping->nrpages == 0)
 		return;
 
-	BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
-	end = (lend >> PAGE_CACHE_SHIFT);
+	/* Adjust start and end so we cover only full pages */
+	if (partial_start)
+		start++;
+	if (partial_end < PAGE_CACHE_SIZE - 1)
+		end--;
 
 	pagevec_init(&pvec, 0);
 	index = start;
 	while (index <= end && pagevec_lookup(&pvec, mapping, index,
-			min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+			min(end - index, (loff_t)PAGEVEC_SIZE - 1) + 1)) {
 		mem_cgroup_uncharge_start();
 		for (i = 0; i < pagevec_count(&pvec); i++) {
 			struct page *page = pvec.pages[i];
@@ -249,21 +265,44 @@ void truncate_inode_pages_range(struct address_space *mapping,
 		index++;
 	}
 
-	if (partial) {
+	/* truncate happened within the page - punch hole */
+	if ((start > end) && (start - end > 1)) {
 		struct page *page = find_lock_page(mapping, start - 1);
 		if (page) {
 			wait_on_page_writeback(page);
-			truncate_partial_page(page, partial);
+			punch_hole_into_page(page, partial_start,
+					     partial_end + 1);
 			unlock_page(page);
 			page_cache_release(page);
 		}
+	} else {
+		/* Partial page truncate at the start of the region */
+		if (partial_start) {
+			struct page *page = find_lock_page(mapping, start - 1);
+			if (page) {
+				wait_on_page_writeback(page);
+				truncate_partial_page(page, partial_start);
+				unlock_page(page);
+				page_cache_release(page);
+			}
+		}
+		/* Partial page truncate at the end of the region */
+		if (partial_end < PAGE_CACHE_SIZE - 1) {
+			struct page *page = find_lock_page(mapping, end + 1);
+			if (page) {
+				wait_on_page_writeback(page);
+				punch_hole_into_page(page, 0, partial_end + 1);
+				unlock_page(page);
+				page_cache_release(page);
+			}
+		}
 	}
 
 	index = start;
-	for ( ; ; ) {
+	while (index <= end) {
 		cond_resched();
 		if (!pagevec_lookup(&pvec, mapping, index,
-			min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+			min(end - index, (loff_t)PAGEVEC_SIZE - 1) + 1)) {
 			if (index == start)
 				break;
 			index = start;
-- 
1.7.7.6

[PATCH 7/8] ext4: use ext4_zero_partial_blocks in punch_hole

[Lukas Czerner]

We're doing to get rid of ext4_discard_partial_page_buffers() since it is
duplicating some code and also partially duplicating work of
truncate_pagecache_range(), moreover the old implementation was much
clearer.

Now when the truncate_inode_pages_range() can handle truncating non page
aligned regions we can use this to invalidate and zero out block aligned
region of the punched out range and then use ext4_block_truncate_page()
to zero the unaligned blocks on the start and end of the range. This
will greatly simplify the punch hole code. Moreover after this commit we
can get rid of the ext4_discard_partial_page_buffers() completely.

This has been tested on ppc64 with 1k block size with fsx and xfstests
without any problems.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 fs/ext4/ext4.h    |    2 +
 fs/ext4/extents.c |   81 ++++++----------------------------------------------
 fs/ext4/inode.c   |   28 ++++++++++++++++++
 3 files changed, 40 insertions(+), 71 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 439af1e..704ceab 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1999,6 +1999,8 @@ extern int ext4_block_truncate_page(handle_t *handle,
 		struct address_space *mapping, loff_t from);
 extern int ext4_block_zero_page_range(handle_t *handle,
 		struct address_space *mapping, loff_t from, loff_t length);
+extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
+			     loff_t lstart, loff_t lend);
 extern int ext4_discard_partial_page_buffers(handle_t *handle,
 		struct address_space *mapping, loff_t from,
 		loff_t length, int flags);
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index ceab5f5..b3300eb 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4742,7 +4742,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 	ext4_lblk_t first_block, stop_block;
 	struct address_space *mapping = inode->i_mapping;
 	handle_t *handle;
-	loff_t first_page, last_page, page_len;
 	loff_t first_page_offset, last_page_offset;
 	int credits, err = 0;
 
@@ -4760,12 +4759,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 		   offset;
 	}
 
-	first_page = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-	last_page = (offset + length) >> PAGE_CACHE_SHIFT;
-
-	first_page_offset = first_page << PAGE_CACHE_SHIFT;
-	last_page_offset = last_page << PAGE_CACHE_SHIFT;
-
 	/*
 	 * Write out all dirty pages to avoid race conditions
 	 * Then release them.
@@ -4778,11 +4771,13 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 			return err;
 	}
 
-	/* Now release the pages */
-	if (last_page_offset > first_page_offset) {
+	first_page_offset = round_up(offset, sb->s_blocksize);
+	last_page_offset = round_down((offset + length), sb->s_blocksize) - 1;
+
+	/* Now release the pages and zero block aligned part of pages*/
+	if (last_page_offset > first_page_offset)
 		truncate_pagecache_range(inode, first_page_offset,
-					 last_page_offset - 1);
-	}
+					 last_page_offset);
 
 	/* finish any pending end_io work */
 	ext4_flush_completed_IO(inode);
@@ -4796,66 +4791,10 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 	if (err)
 		goto out;
 
-	/*
-	 * Now we need to zero out the non-page-aligned data in the
-	 * pages at the start and tail of the hole, and unmap the buffer
-	 * heads for the block aligned regions of the page that were
-	 * completely zeroed.
-	 */
-	if (first_page > last_page) {
-		/*
-		 * If the file space being truncated is contained within a page
-		 * just zero out and unmap the middle of that page
-		 */
-		err = ext4_discard_partial_page_buffers(handle,
-			mapping, offset, length, 0);
-
-		if (err)
-			goto out;
-	} else {
-		/*
-		 * zero out and unmap the partial page that contains
-		 * the start of the hole
-		 */
-		page_len  = first_page_offset - offset;
-		if (page_len > 0) {
-			err = ext4_discard_partial_page_buffers(handle, mapping,
-						   offset, page_len, 0);
-			if (err)
-				goto out;
-		}
-
-		/*
-		 * zero out and unmap the partial page that contains
-		 * the end of the hole
-		 */
-		page_len = offset + length - last_page_offset;
-		if (page_len > 0) {
-			err = ext4_discard_partial_page_buffers(handle, mapping,
-					last_page_offset, page_len, 0);
-			if (err)
-				goto out;
-		}
-	}
-
-	/*
-	 * If i_size is contained in the last page, we need to
-	 * unmap and zero the partial page after i_size
-	 */
-	if (inode->i_size >> PAGE_CACHE_SHIFT == last_page &&
-	   inode->i_size % PAGE_CACHE_SIZE != 0) {
-
-		page_len = PAGE_CACHE_SIZE -
-			(inode->i_size & (PAGE_CACHE_SIZE - 1));
-
-		if (page_len > 0) {
-			err = ext4_discard_partial_page_buffers(handle,
-			  mapping, inode->i_size, page_len, 0);
-
-			if (err)
-				goto out;
-		}
-	}
+	err = ext4_zero_partial_blocks(handle, inode, offset,
+				       offset + length - 1);
+	if (err)
+		goto out;
 
 	first_block = (offset + sb->s_blocksize - 1) >>
 		EXT4_BLOCK_SIZE_BITS(sb);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 588f9fa..28df4f6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3501,6 +3501,34 @@ unlock:
 	return err;
 }
 
+int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
+			     loff_t lstart, loff_t lend)
+{
+	struct super_block *sb = inode->i_sb;
+	unsigned partial = lstart & (sb->s_blocksize - 1);
+	ext4_fsblk_t start = lstart >> sb->s_blocksize_bits;
+	ext4_fsblk_t end = lend >> sb->s_blocksize_bits;
+	int err = 0;
+
+	if (start == end) {
+		err = ext4_block_zero_page_range(handle, inode->i_mapping,
+						 lstart, lend - lstart + 1);
+		return err;
+	}
+	/* Handle partial zero out on the start of the range */
+	if (partial) {
+		err = ext4_block_zero_page_range(handle, inode->i_mapping,
+						 lstart, sb->s_blocksize);
+		if (err)
+			return err;
+	}
+	partial = lend & (sb->s_blocksize - 1);
+	if (partial != sb->s_blocksize - 1)
+		err = ext4_block_zero_page_range(handle, inode->i_mapping,
+						 lend - partial, partial + 1);
+	return err;
+}
+
 int ext4_can_truncate(struct inode *inode)
 {
 	if (S_ISREG(inode->i_mode))
-- 
1.7.7.6

[PATCH 8/8] ext4: remove unused discard_partial_page_buffers

[Lukas Czerner]

The discard_partial_page_buffers is no longer used anywhere so we can
simply remove it including the *_no_lock variant and
EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED define.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 fs/ext4/ext4.h  |    8 --
 fs/ext4/inode.c |  206 -------------------------------------------------------
 2 files changed, 0 insertions(+), 214 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 704ceab..72d75ff 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -583,11 +583,6 @@ enum {
 #define EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER	0x0020
 
 /*
- * Flags used by ext4_discard_partial_page_buffers
- */
-#define EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED	0x0001
-
-/*
  * ioctl commands
  */
 #define	EXT4_IOC_GETFLAGS		FS_IOC_GETFLAGS
@@ -2001,9 +1996,6 @@ extern int ext4_block_zero_page_range(handle_t *handle,
 		struct address_space *mapping, loff_t from, loff_t length);
 extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
 			     loff_t lstart, loff_t lend);
-extern int ext4_discard_partial_page_buffers(handle_t *handle,
-		struct address_space *mapping, loff_t from,
-		loff_t length, int flags);
 extern int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
 extern qsize_t *ext4_get_reserved_space(struct inode *inode);
 extern void ext4_da_update_reserve_space(struct inode *inode,
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 28df4f6..9e3b279 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -138,9 +138,6 @@ static int ext4_set_bh_endio(struct buffer_head *bh, struct inode *inode);
 static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate);
 static int __ext4_journalled_writepage(struct page *page, unsigned int len);
 static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh);
-static int ext4_discard_partial_page_buffers_no_lock(handle_t *handle,
-		struct inode *inode, struct page *page, loff_t from,
-		loff_t length, int flags);
 
 /*
  * Test whether an inode is a fast symlink.
@@ -3178,209 +3175,6 @@ void ext4_set_aops(struct inode *inode)
 	}
 }
 
-
-/*
- * ext4_discard_partial_page_buffers()
- * Wrapper function for ext4_discard_partial_page_buffers_no_lock.
- * This function finds and locks the page containing the offset
- * "from" and passes it to ext4_discard_partial_page_buffers_no_lock.
- * Calling functions that already have the page locked should call
- * ext4_discard_partial_page_buffers_no_lock directly.
- */
-int ext4_discard_partial_page_buffers(handle_t *handle,
-		struct address_space *mapping, loff_t from,
-		loff_t length, int flags)
-{
-	struct inode *inode = mapping->host;
-	struct page *page;
-	int err = 0;
-
-	page = find_or_create_page(mapping, from >> PAGE_CACHE_SHIFT,
-				   mapping_gfp_mask(mapping) & ~__GFP_FS);
-	if (!page)
-		return -ENOMEM;
-
-	err = ext4_discard_partial_page_buffers_no_lock(handle, inode, page,
-		from, length, flags);
-
-	unlock_page(page);
-	page_cache_release(page);
-	return err;
-}
-
-/*
- * ext4_discard_partial_page_buffers_no_lock()
- * Zeros a page range of length 'length' starting from offset 'from'.
- * Buffer heads that correspond to the block aligned regions of the
- * zeroed range will be unmapped.  Unblock aligned regions
- * will have the corresponding buffer head mapped if needed so that
- * that region of the page can be updated with the partial zero out.
- *
- * This function assumes that the page has already been  locked.  The
- * The range to be discarded must be contained with in the given page.
- * If the specified range exceeds the end of the page it will be shortened
- * to the end of the page that corresponds to 'from'.  This function is
- * appropriate for updating a page and it buffer heads to be unmapped and
- * zeroed for blocks that have been either released, or are going to be
- * released.
- *
- * handle: The journal handle
- * inode:  The files inode
- * page:   A locked page that contains the offset "from"
- * from:   The starting byte offset (from the begining of the file)
- *         to begin discarding
- * len:    The length of bytes to discard
- * flags:  Optional flags that may be used:
- *
- *         EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED
- *         Only zero the regions of the page whose buffer heads
- *         have already been unmapped.  This flag is appropriate
- *         for updateing the contents of a page whose blocks may
- *         have already been released, and we only want to zero
- *         out the regions that correspond to those released blocks.
- *
- * Returns zero on sucess or negative on failure.
- */
-static int ext4_discard_partial_page_buffers_no_lock(handle_t *handle,
-		struct inode *inode, struct page *page, loff_t from,
-		loff_t length, int flags)
-{
-	ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT;
-	unsigned int offset = from & (PAGE_CACHE_SIZE-1);
-	unsigned int blocksize, max, pos;
-	ext4_lblk_t iblock;
-	struct buffer_head *bh;
-	int err = 0;
-
-	blocksize = inode->i_sb->s_blocksize;
-	max = PAGE_CACHE_SIZE - offset;
-
-	if (index != page->index)
-		return -EINVAL;
-
-	/*
-	 * correct length if it does not fall between
-	 * 'from' and the end of the page
-	 */
-	if (length > max || length < 0)
-		length = max;
-
-	iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
-
-	if (!page_has_buffers(page))
-		create_empty_buffers(page, blocksize, 0);
-
-	/* Find the buffer that contains "offset" */
-	bh = page_buffers(page);
-	pos = blocksize;
-	while (offset >= pos) {
-		bh = bh->b_this_page;
-		iblock++;
-		pos += blocksize;
-	}
-
-	pos = offset;
-	while (pos < offset + length) {
-		unsigned int end_of_block, range_to_discard;
-
-		err = 0;
-
-		/* The length of space left to zero and unmap */
-		range_to_discard = offset + length - pos;
-
-		/* The length of space until the end of the block */
-		end_of_block = blocksize - (pos & (blocksize-1));
-
-		/*
-		 * Do not unmap or zero past end of block
-		 * for this buffer head
-		 */
-		if (range_to_discard > end_of_block)
-			range_to_discard = end_of_block;
-
-
-		/*
-		 * Skip this buffer head if we are only zeroing unampped
-		 * regions of the page
-		 */
-		if (flags & EXT4_DISCARD_PARTIAL_PG_ZERO_UNMAPPED &&
-			buffer_mapped(bh))
-				goto next;
-
-		/* If the range is block aligned, unmap */
-		if (range_to_discard == blocksize) {
-			clear_buffer_dirty(bh);
-			bh->b_bdev = NULL;
-			clear_buffer_mapped(bh);
-			clear_buffer_req(bh);
-			clear_buffer_new(bh);
-			clear_buffer_delay(bh);
-			clear_buffer_unwritten(bh);
-			clear_buffer_uptodate(bh);
-			zero_user(page, pos, range_to_discard);
-			BUFFER_TRACE(bh, "Buffer discarded");
-			goto next;
-		}
-
-		/*
-		 * If this block is not completely contained in the range
-		 * to be discarded, then it is not going to be released. Because
-		 * we need to keep this block, we need to make sure this part
-		 * of the page is uptodate before we modify it by writeing
-		 * partial zeros on it.
-		 */
-		if (!buffer_mapped(bh)) {
-			/*
-			 * Buffer head must be mapped before we can read
-			 * from the block
-			 */
-			BUFFER_TRACE(bh, "unmapped");
-			ext4_get_block(inode, iblock, bh, 0);
-			/* unmapped? It's a hole - nothing to do */
-			if (!buffer_mapped(bh)) {
-				BUFFER_TRACE(bh, "still unmapped");
-				goto next;
-			}
-		}
-
-		/* Ok, it's mapped. Make sure it's up-to-date */
-		if (PageUptodate(page))
-			set_buffer_uptodate(bh);
-
-		if (!buffer_uptodate(bh)) {
-			err = -EIO;
-			ll_rw_block(READ, 1, &bh);
-			wait_on_buffer(bh);
-			/* Uhhuh. Read error. Complain and punt.*/
-			if (!buffer_uptodate(bh))
-				goto next;
-		}
-
-		if (ext4_should_journal_data(inode)) {
-			BUFFER_TRACE(bh, "get write access");
-			err = ext4_journal_get_write_access(handle, bh);
-			if (err)
-				goto next;
-		}
-
-		zero_user(page, pos, range_to_discard);
-
-		err = 0;
-		if (ext4_should_journal_data(inode)) {
-			err = ext4_handle_dirty_metadata(handle, inode, bh);
-		} else
-			mark_buffer_dirty(bh);
-
-		BUFFER_TRACE(bh, "Partial buffer zeroed");
-next:
-		bh = bh->b_this_page;
-		iblock++;
-		pos += range_to_discard;
-	}
-
-	return err;
-}
-
 /*
  * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
  * up to the end of the block which corresponds to `from'.
-- 
1.7.7.6