>From chris.mason@xxxxxxxxxx Thu Dec 21 15:35:02 2006
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Subject: [PATCH 5 of 8] Make ext3 safe for the new DIO locking rules
X-Mercurial-Node: bebaf8972a3198faf661ab988af0f53cd49856bb
Message-Id: <bebaf8972a3198faf661.1166733301@xxxxxxxxxxxxxxxxxxx>
In-Reply-To: <patchbomb.1166733296@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 21 Dec 2006 15:35:01 -0400
From: Chris Mason <chris.mason@xxxxxxxxxx>
To: linux-fsdevel@xxxxxxxxxxxxxxx, akpm@xxxxxxxx, zach.brown@xxxxxxxxxx
This creates a version of ext3_get_block that starts and ends a transaction.
By starting and ending the transaction inside get_block, this is able to
avoid lock inversion problems when the DIO code tries to take page locks
inside blockdev_direct_IO. (transaction locks must always happen after
page locks).
Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
diff -r 385bc75d9266 -r bebaf8972a31 fs/ext3/inode.c
--- a/fs/ext3/inode.c Thu Dec 21 15:31:30 2006 -0500
+++ b/fs/ext3/inode.c Thu Dec 21 15:31:30 2006 -0500
@@ -1673,6 +1673,30 @@ static int ext3_releasepage(struct page
return journal_try_to_free_buffers(journal, page, wait);
}
+static int ext3_get_block_direct_IO(struct inode *inode, sector_t iblock,
+ struct buffer_head *bh_result, int create)
+{
+ int ret = 0;
+ handle_t *handle = ext3_journal_start(inode, DIO_CREDITS);
+ if (IS_ERR(handle)) {
+ ret = PTR_ERR(handle);
+ goto out;
+ }
+ ret = ext3_get_block(inode, iblock, bh_result, create);
+ /*
+ * Reacquire the handle: ext3_get_block() can restart the transaction
+ */
+ handle = journal_current_handle();
+ if (handle) {
+ int err;
+ err = ext3_journal_stop(handle);
+ if (!ret)
+ ret = err;
+ }
+out:
+ return ret;
+}
+
/*
* If the O_DIRECT write will extend the file then add this inode to the
* orphan list. So recovery will truncate it back to the original size
@@ -1693,39 +1717,58 @@ static ssize_t ext3_direct_IO(int rw, st
int orphan = 0;
size_t count = iov_length(iov, nr_segs);
- if (rw == WRITE) {
- loff_t final_size = offset + count;
-
+ if (rw == WRITE && (offset + count > inode->i_size)) {
handle = ext3_journal_start(inode, DIO_CREDITS);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
goto out;
}
- if (final_size > inode->i_size) {
- ret = ext3_orphan_add(handle, inode);
- if (ret)
- goto out_stop;
- orphan = 1;
- ei->i_disksize = inode->i_size;
- }
- }
-
+ ret = ext3_orphan_add(handle, inode);
+ if (ret) {
+ ext3_journal_stop(handle);
+ goto out;
+ }
+ ei->i_disksize = inode->i_size;
+ ret = ext3_journal_stop(handle);
+ if (ret) {
+ /* something has gone horribly wrong, cleanup
+ * the orphan list in ram
+ */
+ if (inode->i_nlink)
+ ext3_orphan_del(NULL, inode);
+ goto out;
+ }
+ orphan = 1;
+ }
+
+ /*
+ * the placeholder page code may take a page lock, so we have
+ * to stop any running transactions before calling
+ * blockdev_direct_IO. Use ext3_get_block_direct_IO to start
+ * and stop a transaction on each get_block call.
+ */
ret = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
offset, nr_segs,
- ext3_get_block, NULL);
+ ext3_get_block_direct_IO, NULL);
/*
* Reacquire the handle: ext3_get_block() can restart the transaction
*/
handle = journal_current_handle();
-out_stop:
- if (handle) {
+ if (orphan) {
int err;
-
- if (orphan && inode->i_nlink)
+ handle = ext3_journal_start(inode, DIO_CREDITS);
+ if (IS_ERR(handle)) {
+ ret = PTR_ERR(handle);
+ if (inode->i_nlink)
+ ext3_orphan_del(NULL, inode);
+ goto out;
+ }
+
+ if (inode->i_nlink)
ext3_orphan_del(handle, inode);
- if (orphan && ret > 0) {
+ if (ret > 0) {
loff_t end = offset + ret;
if (end > inode->i_size) {
ei->i_disksize = end;
-
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