GFS2 fallocate wasn't properly checking if a blocks were already allocated.
In write_empty_blocks(), if a page didn't have buffer_heads attached, GFS2
was always treating it as if there were no blocks allocated for that page.
GFS2 now calls gfs2_block_map() to check if the blocks are allocated before
writing them out.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
---
fs/gfs2/file.c | 56 +++++++++++++++++++++++++++++++-------------------------
1 file changed, 31 insertions(+), 25 deletions(-)

Index: gfs2-2.6-nmw/fs/gfs2/file.c
================================================== =================
--- gfs2-2.6-nmw.orig/fs/gfs2/file.c
+++ gfs2-2.6-nmw/fs/gfs2/file.c
@@ -622,8 +622,7 @@ static void empty_write_end(struct page
{
struct gfs2_inode *ip = GFS2_I(page->mapping->host);

- page_zero_new_buffers(page, from, to);
- flush_dcache_page(page);
+ zero_user(page, from, to-from);
mark_page_accessed(page);

if (!gfs2_is_writeback(ip))
@@ -632,36 +631,43 @@ static void empty_write_end(struct page
block_commit_write(page, from, to);
}

-static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
+static int needs_empty_write(sector_t block, struct inode *inode)
{
- unsigned start, end, next;
- struct buffer_head *bh, *head;
int error;
+ struct buffer_head bh_map = { .b_state = 0, .b_blocknr = 0 };

- if (!page_has_buffers(page)) {
- error = __block_write_begin(page, from, to - from, gfs2_block_map);
- if (unlikely(error))
- return error;
+ bh_map.b_size = 1 << inode->i_blkbits;
+ error = gfs2_block_map(inode, block, &bh_map, 0);
+ if (unlikely(error))
+ return error;
+ return !buffer_mapped(&bh_map);
+}

- empty_write_end(page, from, to);
- return 0;
- }
+static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
+{
+ struct inode *inode = page->mapping->host;
+ unsigned start, end, next, blksize;
+ sector_t block = page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+ int ret;

- bh = head = page_buffers(page);
+ blksize = 1 << inode->i_blkbits;
next = end = 0;
while (next < from) {
- next += bh->b_size;
- bh = bh->b_this_page;
+ next += blksize;
+ block++;
}
start = next;
do {
- next += bh->b_size;
- if (buffer_mapped(bh)) {
+ next += blksize;
+ ret = needs_empty_write(block, inode);
+ if (unlikely(ret < 0))
+ return ret;
+ if (ret == 0) {
if (end) {
- error = __block_write_begin(page, start, end - start,
- gfs2_block_map);
- if (unlikely(error))
- return error;
+ ret = __block_write_begin(page, start, end - start,
+ gfs2_block_map);
+ if (unlikely(ret))
+ return ret;
empty_write_end(page, start, end);
end = 0;
}
@@ -669,13 +675,13 @@ static int write_empty_blocks(struct pag
}
else
end = next;
- bh = bh->b_this_page;
+ block++;
} while (next < to);

if (end) {
- error = __block_write_begin(page, start, end - start, gfs2_block_map);
- if (unlikely(error))
- return error;
+ ret = __block_write_begin(page, start, end - start, gfs2_block_map);
+ if (unlikely(ret))
+ return ret;
empty_write_end(page, start, end);
}

From: Benjamin Marzinski <bmarzins@redhat.com>

GFS2 fallocate wasn't properly checking if a blocks were already allocated.
In write_empty_blocks(), if a page didn't have buffer_heads attached, GFS2
was always treating it as if there were no blocks allocated for that page.
GFS2 now calls gfs2_block_map() to check if the blocks are allocated before
writing them out.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 2878481..4074b95 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -622,8 +622,7 @@ static void empty_write_end(struct page *page, unsigned from,
{
struct gfs2_inode *ip = GFS2_I(page->mapping->host);

- page_zero_new_buffers(page, from, to);
- flush_dcache_page(page);
+ zero_user(page, from, to-from);
mark_page_accessed(page);

if (!gfs2_is_writeback(ip))
@@ -632,36 +631,43 @@ static void empty_write_end(struct page *page, unsigned from,
block_commit_write(page, from, to);
}

-static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
+static int needs_empty_write(sector_t block, struct inode *inode)
{
- unsigned start, end, next;
- struct buffer_head *bh, *head;
int error;
+ struct buffer_head bh_map = { .b_state = 0, .b_blocknr = 0 };

- if (!page_has_buffers(page)) {
- error = __block_write_begin(page, from, to - from, gfs2_block_map);
- if (unlikely(error))
- return error;
+ bh_map.b_size = 1 << inode->i_blkbits;
+ error = gfs2_block_map(inode, block, &bh_map, 0);
+ if (unlikely(error))
+ return error;
+ return !buffer_mapped(&bh_map);
+}

- empty_write_end(page, from, to);
- return 0;
- }
+static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
+{
+ struct inode *inode = page->mapping->host;
+ unsigned start, end, next, blksize;
+ sector_t block = page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+ int ret;

- bh = head = page_buffers(page);
+ blksize = 1 << inode->i_blkbits;
next = end = 0;
while (next < from) {
- next += bh->b_size;
- bh = bh->b_this_page;
+ next += blksize;
+ block++;
}
start = next;
do {
- next += bh->b_size;
- if (buffer_mapped(bh)) {
+ next += blksize;
+ ret = needs_empty_write(block, inode);
+ if (unlikely(ret < 0))
+ return ret;
+ if (ret == 0) {
if (end) {
- error = __block_write_begin(page, start, end - start,
- gfs2_block_map);
- if (unlikely(error))
- return error;
+ ret = __block_write_begin(page, start, end - start,
+ gfs2_block_map);
+ if (unlikely(ret))
+ return ret;
empty_write_end(page, start, end);
end = 0;
}
@@ -669,13 +675,13 @@ static int write_empty_blocks(struct page *page, unsigned from, unsigned to)
}
else
end = next;
- bh = bh->b_this_page;
+ block++;
} while (next < to);

if (end) {
- error = __block_write_begin(page, start, end - start, gfs2_block_map);
- if (unlikely(error))
- return error;
+ ret = __block_write_begin(page, start, end - start, gfs2_block_map);
+ if (unlikely(ret))
+ return ret;
empty_write_end(page, start, end);
}

--
1.7.4