ocfs2: take data locks around extend
We need to take a data lock around extends to protect the pages that
ocfs2_zero_extend is going to be pulling into the page cache. Otherwise an
extend on one node might populate the page cache with data pages that have
no lock coverage.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 0d858d0..47152bf 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -276,13 +276,29 @@
return ret;
}
+/* This can also be called from ocfs2_write_zero_page() which has done
+ * it's own cluster locking. */
+int ocfs2_prepare_write_nolock(struct inode *inode, struct page *page,
+ unsigned from, unsigned to)
+{
+ int ret;
+
+ down_read(&OCFS2_I(inode)->ip_alloc_sem);
+
+ ret = block_prepare_write(page, from, to, ocfs2_get_block);
+
+ up_read(&OCFS2_I(inode)->ip_alloc_sem);
+
+ return ret;
+}
+
/*
* ocfs2_prepare_write() can be an outer-most ocfs2 call when it is called
* from loopback. It must be able to perform its own locking around
* ocfs2_get_block().
*/
-int ocfs2_prepare_write(struct file *file, struct page *page,
- unsigned from, unsigned to)
+static int ocfs2_prepare_write(struct file *file, struct page *page,
+ unsigned from, unsigned to)
{
struct inode *inode = page->mapping->host;
int ret;
@@ -295,11 +311,7 @@
goto out;
}
- down_read(&OCFS2_I(inode)->ip_alloc_sem);
-
- ret = block_prepare_write(page, from, to, ocfs2_get_block);
-
- up_read(&OCFS2_I(inode)->ip_alloc_sem);
+ ret = ocfs2_prepare_write_nolock(inode, page, from, to);
ocfs2_meta_unlock(inode, 0);
out:
@@ -625,11 +637,31 @@
int ret;
mlog_entry_void();
+
+ /*
+ * We get PR data locks even for O_DIRECT. This allows
+ * concurrent O_DIRECT I/O but doesn't let O_DIRECT with
+ * extending and buffered zeroing writes race. If they did
+ * race then the buffered zeroing could be written back after
+ * the O_DIRECT I/O. It's one thing to tell people not to mix
+ * buffered and O_DIRECT writes, but expecting them to
+ * understand that file extension is also an implicit buffered
+ * write is too much. By getting the PR we force writeback of
+ * the buffered zeroing before proceeding.
+ */
+ ret = ocfs2_data_lock(inode, 0);
+ if (ret < 0) {
+ mlog_errno(ret);
+ goto out;
+ }
+ ocfs2_data_unlock(inode, 0);
+
ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
inode->i_sb->s_bdev, iov, offset,
nr_segs,
ocfs2_direct_IO_get_blocks,
ocfs2_dio_end_io);
+out:
mlog_exit(ret);
return ret;
}
diff --git a/fs/ocfs2/aops.h b/fs/ocfs2/aops.h
index d40456d..e88c3f0 100644
--- a/fs/ocfs2/aops.h
+++ b/fs/ocfs2/aops.h
@@ -22,8 +22,8 @@
#ifndef OCFS2_AOPS_H
#define OCFS2_AOPS_H
-int ocfs2_prepare_write(struct file *file, struct page *page,
- unsigned from, unsigned to);
+int ocfs2_prepare_write_nolock(struct inode *inode, struct page *page,
+ unsigned from, unsigned to);
struct ocfs2_journal_handle *ocfs2_start_walk_page_trans(struct inode *inode,
struct page *page,
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 581eb45..20fffeed 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -613,7 +613,8 @@
/* Some parts of this taken from generic_cont_expand, which turned out
* to be too fragile to do exactly what we need without us having to
- * worry about recursive locking in ->commit_write(). */
+ * worry about recursive locking in ->prepare_write() and
+ * ->commit_write(). */
static int ocfs2_write_zero_page(struct inode *inode,
u64 size)
{
@@ -641,7 +642,7 @@
goto out;
}
- ret = ocfs2_prepare_write(NULL, page, offset, offset);
+ ret = ocfs2_prepare_write_nolock(inode, page, offset, offset);
if (ret < 0) {
mlog_errno(ret);
goto out_unlock;
@@ -695,13 +696,26 @@
return ret;
}
+/*
+ * A tail_to_skip value > 0 indicates that we're being called from
+ * ocfs2_file_aio_write(). This has the following implications:
+ *
+ * - we don't want to update i_size
+ * - di_bh will be NULL, which is fine because it's only used in the
+ * case where we want to update i_size.
+ * - ocfs2_zero_extend() will then only be filling the hole created
+ * between i_size and the start of the write.
+ */
static int ocfs2_extend_file(struct inode *inode,
struct buffer_head *di_bh,
- u64 new_i_size)
+ u64 new_i_size,
+ size_t tail_to_skip)
{
int ret = 0;
u32 clusters_to_add;
+ BUG_ON(!tail_to_skip && !di_bh);
+
/* setattr sometimes calls us like this. */
if (new_i_size == 0)
goto out;
@@ -714,27 +728,44 @@
OCFS2_I(inode)->ip_clusters;
if (clusters_to_add) {
+ /*
+ * protect the pages that ocfs2_zero_extend is going to
+ * be pulling into the page cache.. we do this before the
+ * metadata extend so that we don't get into the situation
+ * where we've extended the metadata but can't get the data
+ * lock to zero.
+ */
+ ret = ocfs2_data_lock(inode, 1);
+ if (ret < 0) {
+ mlog_errno(ret);
+ goto out;
+ }
+
ret = ocfs2_extend_allocation(inode, clusters_to_add);
if (ret < 0) {
mlog_errno(ret);
- goto out;
+ goto out_unlock;
}
- ret = ocfs2_zero_extend(inode, new_i_size);
+ ret = ocfs2_zero_extend(inode, (u64)new_i_size - tail_to_skip);
if (ret < 0) {
mlog_errno(ret);
- goto out;
+ goto out_unlock;
}
- }
-
- /* No allocation required, we just use this helper to
- * do a trivial update of i_size. */
- ret = ocfs2_simple_size_update(inode, di_bh, new_i_size);
- if (ret < 0) {
- mlog_errno(ret);
- goto out;
}
+ if (!tail_to_skip) {
+ /* We're being called from ocfs2_setattr() which wants
+ * us to update i_size */
+ ret = ocfs2_simple_size_update(inode, di_bh, new_i_size);
+ if (ret < 0)
+ mlog_errno(ret);
+ }
+
+out_unlock:
+ if (clusters_to_add) /* this is the only case in which we lock */
+ ocfs2_data_unlock(inode, 1);
+
out:
return ret;
}
@@ -793,7 +824,7 @@
if (i_size_read(inode) > attr->ia_size)
status = ocfs2_truncate_file(inode, bh, attr->ia_size);
else
- status = ocfs2_extend_file(inode, bh, attr->ia_size);
+ status = ocfs2_extend_file(inode, bh, attr->ia_size, 0);
if (status < 0) {
if (status != -ENOSPC)
mlog_errno(status);
@@ -1049,21 +1080,12 @@
if (!clusters)
break;
- ret = ocfs2_extend_allocation(inode, clusters);
+ ret = ocfs2_extend_file(inode, NULL, newsize, count);
if (ret < 0) {
if (ret != -ENOSPC)
mlog_errno(ret);
goto out;
}
-
- /* Fill any holes which would've been created by this
- * write. If we're O_APPEND, this will wind up
- * (correctly) being a noop. */
- ret = ocfs2_zero_extend(inode, (u64) newsize - count);
- if (ret < 0) {
- mlog_errno(ret);
- goto out;
- }
break;
}