[PATCH] fix garbage instead of zeroes in UFS
Looks like this is the problem, which point Al Viro some time ago:
ufs's get_block callback allocates 16k of disk at a time, and links that
entire 16k into the file's metadata. But because get_block is called for only
a single buffer_head (a 2k buffer_head in this case?) we are only able to tell
the VFS that this 2k is buffer_new().
So when ufs_getfrag_block() is later called to map some more data in the file,
and when that data resides within the remaining 14k of this fragment,
ufs_getfrag_block() will incorrectly return a !buffer_new() buffer_head.
I don't see _right_ way to do nullification of whole block, if use inode
page cache, some pages may be outside of inode limits (inode size), and
will be lost; if use blockdev page cache it is possible to zero real data,
if later inode page cache will be used.
The simpliest way, as can I see usage of block device page cache, but not only
mark dirty, but also sync it during "nullification". I use my simple tests
collection, which I used for check that create,open,write,read,close works on
ufs, and I see that this patch makes ufs code 18% slower then before.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/ufs/balloc.c b/fs/ufs/balloc.c
index b823814..2e0021e 100644
--- a/fs/ufs/balloc.c
+++ b/fs/ufs/balloc.c
@@ -275,6 +275,25 @@
UFSD("EXIT\n");
}
+static void ufs_clear_frags(struct inode *inode, sector_t beg, unsigned int n,
+ int sync)
+{
+ struct buffer_head *bh;
+ sector_t end = beg + n;
+
+ for (; beg < end; ++beg) {
+ bh = sb_getblk(inode->i_sb, beg);
+ lock_buffer(bh);
+ memset(bh->b_data, 0, inode->i_sb->s_blocksize);
+ set_buffer_uptodate(bh);
+ mark_buffer_dirty(bh);
+ unlock_buffer(bh);
+ if (IS_SYNC(inode) || sync)
+ sync_dirty_buffer(bh);
+ brelse(bh);
+ }
+}
+
unsigned ufs_new_fragments(struct inode * inode, __fs32 * p, unsigned fragment,
unsigned goal, unsigned count, int * err, struct page *locked_page)
{
@@ -350,6 +369,8 @@
*p = cpu_to_fs32(sb, result);
*err = 0;
UFS_I(inode)->i_lastfrag = max_t(u32, UFS_I(inode)->i_lastfrag, fragment + count);
+ ufs_clear_frags(inode, result + oldcount, newcount - oldcount,
+ locked_page != NULL);
}
unlock_super(sb);
UFSD("EXIT, result %u\n", result);
@@ -363,6 +384,8 @@
if (result) {
*err = 0;
UFS_I(inode)->i_lastfrag = max_t(u32, UFS_I(inode)->i_lastfrag, fragment + count);
+ ufs_clear_frags(inode, result + oldcount, newcount - oldcount,
+ locked_page != NULL);
unlock_super(sb);
UFSD("EXIT, result %u\n", result);
return result;
@@ -398,6 +421,8 @@
*p = cpu_to_fs32(sb, result);
*err = 0;
UFS_I(inode)->i_lastfrag = max_t(u32, UFS_I(inode)->i_lastfrag, fragment + count);
+ ufs_clear_frags(inode, result + oldcount, newcount - oldcount,
+ locked_page != NULL);
unlock_super(sb);
if (newcount < request)
ufs_free_fragments (inode, result + newcount, request - newcount);