[PATCH 2/3] ocfs2: Zero the tail cluster when extending past i_size.

From: Joel Becker
Date: Wed Jul 07 2010 - 07:46:45 EST

ocfs2's allocation unit is the cluster. This can be larger than a block
or even a memory page. This means that a file may have many blocks in
its last extent that are beyond the block containing i_size. There also
may be more unwritten extents after that.

When ocfs2 grows a file, it zeros the entire cluster in order to ensure
future i_size growth will see cleared blocks. Unfortunately,
block_write_full_page() drops the pages past i_size. This means that
ocfs2 is actually leaking garbage data into the tail end of that last
cluster. This is a bug.

We adjust ocfs2_write_begin_nolock() and ocfs2_extend_file() to detect
when a write or truncate is past i_size. They will use
ocfs2_zero_extend() to ensure the data is properly zeroed.

Older versions of ocfs2_zero_extend() simply zeroed every block between
i_size and the zeroing position. This presumes three things:

1) There is allocation for all of these blocks.
2) The extents are not unwritten.
3) The extents are not refcounted.

(1) and (2) hold true for non-sparse filesystems, which used to be the
only users of ocfs2_zero_extend(). (3) is another bug.

Since we're now using ocfs2_zero_extend() for sparse filesystems as
well, we teach ocfs2_zero_extend() to check every extent between
i_size and the zeroing position. If the extent is unwritten, it is
ignored. If it is refcounted, it is CoWed. Then it is zeroed.

Signed-off-by: Joel Becker <joel.becker@xxxxxxxxxx>
---
fs/ocfs2/aops.c | 30 ++++----
fs/ocfs2/file.c | 198 ++++++++++++++++++++++++++++++++++++++--------
fs/ocfs2/file.h | 6 +-
fs/ocfs2/quota_global.c | 2 +-
fs/ocfs2/quota_local.c | 4 +-
fs/ocfs2/refcounttree.c | 6 ++
6 files changed, 192 insertions(+), 54 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 9a5c931..8d6dc3f 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -196,15 +196,14 @@ int ocfs2_get_block(struct inode *inode, sector_t iblock,
dump_stack();
goto bail;
}
-
- past_eof = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
- mlog(0, "Inode %lu, past_eof = %llu\n", inode->i_ino,
- (unsigned long long)past_eof);
-
- if (create && (iblock >= past_eof))
- set_buffer_new(bh_result);
}

+ past_eof = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
+ mlog(0, "Inode %lu, past_eof = %llu\n", inode->i_ino,
+ (unsigned long long)past_eof);
+ if (create && (iblock >= past_eof))
+ set_buffer_new(bh_result);
+
bail:
if (err < 0)
err = -EIO;
@@ -1590,21 +1589,20 @@ out:
* write path can treat it as an non-allocating write, which has no
* special case code for sparse/nonsparse files.
*/
-static int ocfs2_expand_nonsparse_inode(struct inode *inode, loff_t pos,
- unsigned len,
+static int ocfs2_expand_nonsparse_inode(struct inode *inode,
+ struct buffer_head *di_bh,
+ loff_t pos, unsigned len,
struct ocfs2_write_ctxt *wc)
{
int ret;
- struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
loff_t newsize = pos + len;

- if (ocfs2_sparse_alloc(osb))
- return 0;
+ BUG_ON(ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)));

if (newsize <= i_size_read(inode))
return 0;

- ret = ocfs2_extend_no_holes(inode, newsize, pos);
+ ret = ocfs2_extend_no_holes(inode, di_bh, newsize, pos);
if (ret)
mlog_errno(ret);

@@ -1649,7 +1647,11 @@ int ocfs2_write_begin_nolock(struct address_space *mapping,
}
}

- ret = ocfs2_expand_nonsparse_inode(inode, pos, len, wc);
+ if (ocfs2_sparse_alloc(osb))
+ ret = ocfs2_zero_extend(inode, di_bh, pos);
+ else
+ ret = ocfs2_expand_nonsparse_inode(inode, di_bh, pos, len,
+ wc);
if (ret) {
mlog_errno(ret);
goto out;
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index a6e0eb6..1fdc45a 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -787,6 +787,11 @@ static int ocfs2_write_zero_page(struct inode *inode, u64 abs_from,
if (!zero_to)
zero_to = PAGE_CACHE_SIZE;

+ mlog(0,
+ "abs_from = %llu, abs_to = %llu, index = %lu, zero_from = %u, zero_to = %u\n",
+ (unsigned long long)abs_from, (unsigned long long)abs_to,
+ index, zero_from, zero_to);
+
/* We know that zero_from is block aligned */
for (block_start = zero_from;
(block_start < PAGE_CACHE_SIZE) && (block_start < zero_to);
@@ -834,25 +839,114 @@ out:
return ret;
}

-static int ocfs2_zero_extend(struct inode *inode,
- u64 zero_to_size)
+/*
+ * Find the next range to zero. We do this in terms of bytes because
+ * that's what ocfs2_zero_extend() wants, and it is dealing with the
+ * pagecache. We may return multiple extents.
+ *
+ * zero_start and zero_end are ocfs2_zero_extend()s current idea of what
+ * needs to be zeroed. range_start and range_end return the next zeroing
+ * range. A subsequent call should pass the previous range_end as its
+ * zero_start. If range_end is 0, there's nothing to do.
+ *
+ * Unwritten extents are skipped over. Refcounted extents are CoWd.
+ */
+static int ocfs2_zero_extend_get_range(struct inode *inode,
+ struct buffer_head *di_bh,
+ u64 zero_start, u64 zero_end,
+ u64 *range_start, u64 *range_end)
{
- int ret = 0;
- u64 start_off, next_off;
- struct super_block *sb = inode->i_sb;
+ int rc = 0, needs_cow = 0;
+ u32 p_cpos, zero_clusters = 0;
+ u32 zero_cpos =
+ zero_start >> OCFS2_SB(inode->i_sb)->s_clustersize_bits;
+ u32 last_cpos = ocfs2_clusters_for_bytes(inode->i_sb, zero_end);
+ unsigned int num_clusters = 0;
+ unsigned int ext_flags = 0;

- start_off = ocfs2_align_bytes_to_blocks(sb, i_size_read(inode));
- while (start_off < zero_to_size) {
- next_off = (start_off & PAGE_CACHE_MASK) + PAGE_CACHE_SIZE;
- if (next_off > zero_to_size)
- next_off = zero_to_size;
- ret = ocfs2_write_zero_page(inode, start_off, next_off);
- if (ret < 0) {
- mlog_errno(ret);
+ while (zero_cpos < last_cpos) {
+ rc = ocfs2_get_clusters(inode, zero_cpos, &p_cpos,
+ &num_clusters, &ext_flags);
+ if (rc) {
+ mlog_errno(rc);
+ goto out;
+ }
+
+ if (p_cpos && !(ext_flags & OCFS2_EXT_UNWRITTEN)) {
+ zero_clusters = num_clusters;
+ if (ext_flags & OCFS2_EXT_REFCOUNTED)
+ needs_cow = 1;
+ break;
+ }
+
+ zero_cpos += num_clusters;
+ }
+ if (!zero_clusters) {
+ *range_end = 0;
+ goto out;
+ }
+
+ while ((zero_cpos + zero_clusters) < last_cpos) {
+ rc = ocfs2_get_clusters(inode, zero_cpos + zero_clusters,
+ &p_cpos, &num_clusters,
+ &ext_flags);
+ if (rc) {
+ mlog_errno(rc);
+ goto out;
+ }
+
+ if (!p_cpos || (ext_flags & OCFS2_EXT_UNWRITTEN))
+ break;
+ if (ext_flags & OCFS2_EXT_REFCOUNTED)
+ needs_cow = 1;
+ zero_clusters += num_clusters;
+ }
+ if ((zero_cpos + zero_clusters) > last_cpos)
+ zero_clusters = last_cpos - zero_cpos;
+
+ if (needs_cow) {
+ rc = ocfs2_refcount_cow(inode, di_bh, zero_cpos, zero_clusters,
+ UINT_MAX);
+ if (rc) {
+ mlog_errno(rc);
goto out;
}
+ }

- start_off = next_off;
+ *range_start = ocfs2_clusters_to_bytes(inode->i_sb, zero_cpos);
+ *range_end = ocfs2_clusters_to_bytes(inode->i_sb,
+ zero_cpos + zero_clusters);
+
+out:
+ return rc;
+}
+
+/*
+ * Zero one range returned from ocfs2_zero_extend_get_range(). The caller
+ * has made sure that the entire range needs zeroing.
+ */
+static int ocfs2_zero_extend_range(struct inode *inode, u64 range_start,
+ u64 range_end)
+{
+ int rc = 0;
+ u64 next_pos;
+ u64 zero_pos = range_start;
+
+ mlog(0, "range_start = %llu, range_end = %llu\n",
+ (unsigned long long)range_start,
+ (unsigned long long)range_end);
+ BUG_ON(range_start >= range_end);
+
+ while (zero_pos < range_end) {
+ next_pos = (zero_pos & PAGE_CACHE_MASK) + PAGE_CACHE_SIZE;
+ if (next_pos > range_end)
+ next_pos = range_end;
+ rc = ocfs2_write_zero_page(inode, zero_pos, next_pos);
+ if (rc < 0) {
+ mlog_errno(rc);
+ break;
+ }
+ zero_pos = next_pos;

/*
* Very large extends have the potential to lock up
@@ -861,16 +955,60 @@ static int ocfs2_zero_extend(struct inode *inode,
cond_resched();
}

-out:
+ return rc;
+}
+
+int ocfs2_zero_extend(struct inode *inode, struct buffer_head *di_bh,
+ loff_t zero_to_size)
+{
+ int ret = 0;
+ u64 zero_start, range_start = 0, range_end = 0;
+ struct super_block *sb = inode->i_sb;
+
+ zero_start = ocfs2_align_bytes_to_blocks(sb, i_size_read(inode));
+ while (zero_start < zero_to_size) {
+ ret = ocfs2_zero_extend_get_range(inode, di_bh, zero_start,
+ zero_to_size,
+ &range_start,
+ &range_end);
+ if (ret) {
+ mlog_errno(ret);
+ break;
+ }
+ if (!range_end)
+ break;
+ /* Trim the ends */
+ if (range_start < zero_start)
+ range_start = zero_start;
+ if (range_end > zero_to_size)
+ range_end = zero_to_size;
+
+ ret = ocfs2_zero_extend_range(inode, range_start,
+ range_end);
+ if (ret) {
+ mlog_errno(ret);
+ break;
+ }
+ zero_start = range_end;
+ }
+
return ret;
}

-int ocfs2_extend_no_holes(struct inode *inode, u64 new_i_size, u64 zero_to)
+int ocfs2_extend_no_holes(struct inode *inode, struct buffer_head *di_bh,
+ u64 new_i_size, u64 zero_to)
{
int ret;
u32 clusters_to_add;
struct ocfs2_inode_info *oi = OCFS2_I(inode);

+ /*
+ * Only quota files call this without a bh, and they can't be
+ * refcounted.
+ */
+ BUG_ON(!di_bh && (oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));
+ BUG_ON(!di_bh && !(oi->ip_flags & OCFS2_INODE_SYSTEM_FILE));
+
clusters_to_add = ocfs2_clusters_for_bytes(inode->i_sb, new_i_size);
if (clusters_to_add < oi->ip_clusters)
clusters_to_add = 0;
@@ -891,7 +1029,7 @@ int ocfs2_extend_no_holes(struct inode *inode, u64 new_i_size, u64 zero_to)
* still need to zero the area between the old i_size and the
* new i_size.
*/
- ret = ocfs2_zero_extend(inode, zero_to);
+ ret = ocfs2_zero_extend(inode, di_bh, zero_to);
if (ret < 0)
mlog_errno(ret);

@@ -913,27 +1051,15 @@ static int ocfs2_extend_file(struct inode *inode,
goto out;

if (i_size_read(inode) == new_i_size)
- goto out;
+ goto out;
BUG_ON(new_i_size < i_size_read(inode));

/*
- * Fall through for converting inline data, even if the fs
- * supports sparse files.
- *
- * The check for inline data here is legal - nobody can add
- * the feature since we have i_mutex. We must check it again
- * after acquiring ip_alloc_sem though, as paths like mmap
- * might have raced us to converting the inode to extents.
- */
- if (!(oi->ip_dyn_features & OCFS2_INLINE_DATA_FL)
- && ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
- goto out_update_size;
-
- /*
* The alloc sem blocks people in read/write from reading our
* allocation until we're done changing it. We depend on
* i_mutex to block other extend/truncate calls while we're
- * here.
+ * here. We even have to hold it for sparse files because there
+ * might be some tail zeroing.
*/
down_write(&oi->ip_alloc_sem);

@@ -950,14 +1076,16 @@ static int ocfs2_extend_file(struct inode *inode,
ret = ocfs2_convert_inline_data_to_extents(inode, di_bh);
if (ret) {
up_write(&oi->ip_alloc_sem);
-
mlog_errno(ret);
goto out;
}
}

- if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
- ret = ocfs2_extend_no_holes(inode, new_i_size, new_i_size);
+ if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
+ ret = ocfs2_zero_extend(inode, di_bh, new_i_size);
+ else
+ ret = ocfs2_extend_no_holes(inode, di_bh, new_i_size,
+ new_i_size);

up_write(&oi->ip_alloc_sem);

diff --git a/fs/ocfs2/file.h b/fs/ocfs2/file.h
index d66cf4f..97bf761 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -54,8 +54,10 @@ int ocfs2_add_inode_data(struct ocfs2_super *osb,
int ocfs2_simple_size_update(struct inode *inode,
struct buffer_head *di_bh,
u64 new_i_size);
-int ocfs2_extend_no_holes(struct inode *inode, u64 new_i_size,
- u64 zero_to);
+int ocfs2_extend_no_holes(struct inode *inode, struct buffer_head *di_bh,
+ u64 new_i_size, u64 zero_to);
+int ocfs2_zero_extend(struct inode *inode, struct buffer_head *di_bh,
+ loff_t zero_to);
int ocfs2_setattr(struct dentry *dentry, struct iattr *attr);
int ocfs2_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat);
diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c
index 2bb35fe..4607923 100644
--- a/fs/ocfs2/quota_global.c
+++ b/fs/ocfs2/quota_global.c
@@ -775,7 +775,7 @@ static int ocfs2_acquire_dquot(struct dquot *dquot)
* locking allocators ranks above a transaction start
*/
WARN_ON(journal_current_handle());
- status = ocfs2_extend_no_holes(gqinode,
+ status = ocfs2_extend_no_holes(gqinode, NULL,
gqinode->i_size + (need_alloc << sb->s_blocksize_bits),
gqinode->i_size);
if (status < 0)
diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c
index 8bd70d4..dc78764 100644
--- a/fs/ocfs2/quota_local.c
+++ b/fs/ocfs2/quota_local.c
@@ -971,7 +971,7 @@ static struct ocfs2_quota_chunk *ocfs2_local_quota_add_chunk(
u64 p_blkno;

/* We are protected by dqio_sem so no locking needed */
- status = ocfs2_extend_no_holes(lqinode,
+ status = ocfs2_extend_no_holes(lqinode, NULL,
lqinode->i_size + 2 * sb->s_blocksize,
lqinode->i_size);
if (status < 0) {
@@ -1114,7 +1114,7 @@ static struct ocfs2_quota_chunk *ocfs2_extend_local_quota_file(
return ocfs2_local_quota_add_chunk(sb, type, offset);

/* We are protected by dqio_sem so no locking needed */
- status = ocfs2_extend_no_holes(lqinode,
+ status = ocfs2_extend_no_holes(lqinode, NULL,
lqinode->i_size + sb->s_blocksize,
lqinode->i_size);
if (status < 0) {
diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 4793f36..32949df 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -4166,6 +4166,12 @@ static int __ocfs2_reflink(struct dentry *old_dentry,
struct inode *inode = old_dentry->d_inode;
struct buffer_head *new_bh = NULL;

+ if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_SYSTEM_FILE) {
+ ret = -EINVAL;
+ mlog_errno(ret);
+ goto out;
+ }
+
ret = filemap_fdatawrite(inode->i_mapping);
if (ret) {
mlog_errno(ret);
--
1.7.1

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