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Hi Alan,
I'm sending you a patch which fixes a deadlock when quota is used on
ext3. There is lock inversion on dqio_sem and journal_start/stop. The
patch introduces needed framework for ext3 to start transaction before
dqio_sem is acquired. Please apply.
Bye
Honza
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Content-Disposition: attachment; filename="quota-2.4.21-pre5-ac3-2-ext3deadlock.diff"
diff -ruNX /home/jack/.kerndiffexclude linux-2.4.21-pre5-ac3-1-syncall/fs/dquot.c linux-2.4.21-pre5-ac3-2-ext3deadlock/fs/dquot.c
--- linux-2.4.21-pre5-ac3-1-syncall/fs/dquot.c Tue Apr 1 21:08:39 2003
+++ linux-2.4.21-pre5-ac3-2-ext3deadlock/fs/dquot.c Mon Apr 14 23:55:34 2003
@@ -397,7 +397,7 @@
if (dquot->dq_flags & DQ_LOCKED)
wait_on_dquot(dquot);
if (dquot_dirty(dquot))
- commit_dqblk(dquot);
+ sb->dq_op->sync_dquot(dquot);
dqput(dquot);
goto restart;
}
@@ -1221,9 +1221,16 @@
alloc_inode: dquot_alloc_inode,
free_space: dquot_free_space,
free_inode: dquot_free_inode,
- transfer: dquot_transfer
+ transfer: dquot_transfer,
+ sync_dquot: commit_dqblk
};
+/* Function used by filesystems for initializing the dquot_operations structure */
+void init_dquot_operations(struct dquot_operations *fsdqops)
+{
+ memcpy(fsdqops, &dquot_operations, sizeof(dquot_operations));
+}
+
static inline void set_enable_flags(struct quota_info *dqopt, int type)
{
switch (type) {
@@ -1519,3 +1526,4 @@
EXPORT_SYMBOL(register_quota_format);
EXPORT_SYMBOL(unregister_quota_format);
EXPORT_SYMBOL(dqstats);
+EXPORT_SYMBOL(init_dquot_operations);
diff -ruNX /home/jack/.kerndiffexclude linux-2.4.21-pre5-ac3-1-syncall/fs/ext3/super.c linux-2.4.21-pre5-ac3-2-ext3deadlock/fs/ext3/super.c
--- linux-2.4.21-pre5-ac3-1-syncall/fs/ext3/super.c Tue Apr 1 21:06:22 2003
+++ linux-2.4.21-pre5-ac3-2-ext3deadlock/fs/ext3/super.c Mon Apr 14 23:58:24 2003
@@ -448,6 +448,9 @@
return;
}
+static struct dquot_operations ext3_qops;
+static int (*old_sync_dquot)(struct dquot *dquot);
+
static struct super_operations ext3_sops = {
read_inode: ext3_read_inode, /* BKL held */
write_inode: ext3_write_inode, /* BKL not held. Don't need */
@@ -1128,6 +1131,7 @@
* set up enough so that it can read an inode
*/
sb->s_op = &ext3_sops;
+ sb->dq_op = &ext3_qops;
INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
sb->s_root = 0;
@@ -1758,10 +1762,63 @@
return 0;
}
+/* Helper function for writing quotas on sync - we need to start transaction before quota file
+ * is locked for write. Otherwise the are possible deadlocks:
+ * Process 1 Process 2
+ * ext3_create() quota_sync()
+ * journal_start() write_dquot()
+ * DQUOT_INIT() down(dqio_sem)
+ * down(dqio_sem) journal_start()
+ *
+ */
+
+#ifdef CONFIG_QUOTA
+
+#define EXT3_OLD_QFMT_BLOCKS 2
+#define EXT3_V0_QFMT_BLOCKS 6
+
+static int ext3_sync_dquot(struct dquot *dquot)
+{
+ int nblocks, ret;
+ handle_t *handle;
+ struct quota_info *dqops = sb_dqopt(dquot->dq_sb);
+ struct inode *qinode;
+
+ switch (dqops->info[dquot->dq_type].dqi_format->qf_fmt_id) {
+ case QFMT_VFS_OLD:
+ nblocks = EXT3_OLD_QFMT_BLOCKS;
+ break;
+ case QFMT_VFS_V0:
+ nblocks = EXT3_V0_QFMT_BLOCKS;
+ break;
+ default:
+ nblocks = EXT3_MAX_TRANS_DATA;
+ }
+ lock_kernel();
+ qinode = dqops->files[dquot->dq_type]->f_dentry->d_inode;
+ handle = ext3_journal_start(qinode, nblocks);
+ if (IS_ERR(handle)) {
+ unlock_kernel();
+ return PTR_ERR(handle);
+ }
+ unlock_kernel();
+ ret = old_sync_dquot(dquot);
+ lock_kernel();
+ ret = ext3_journal_stop(handle, qinode);
+ unlock_kernel();
+ return ret;
+}
+#endif
+
static DECLARE_FSTYPE_DEV(ext3_fs_type, "ext3", ext3_read_super);
static int __init init_ext3_fs(void)
{
+#ifdef CONFIG_QUOTA
+ init_dquot_operations(&ext3_qops);
+ old_sync_dquot = ext3_qops.sync_dquot;
+ ext3_qops.sync_dquot = ext3_sync_dquot;
+#endif
return register_filesystem(&ext3_fs_type);
}
diff -ruNX /home/jack/.kerndiffexclude linux-2.4.21-pre5-ac3-1-syncall/include/linux/quota.h linux-2.4.21-pre5-ac3-2-ext3deadlock/include/linux/quota.h
--- linux-2.4.21-pre5-ac3-1-syncall/include/linux/quota.h Tue Apr 1 21:19:44 2003
+++ linux-2.4.21-pre5-ac3-2-ext3deadlock/include/linux/quota.h Tue Apr 15 21:07:51 2003
@@ -251,6 +251,7 @@
void (*free_space) (struct inode *, qsize_t);
void (*free_inode) (const struct inode *, unsigned long);
int (*transfer) (struct inode *, struct iattr *);
+ int (*sync_dquot) (struct dquot *);
};
/* Operations handling requests from userspace */
@@ -312,6 +313,7 @@
int register_quota_format(struct quota_format_type *fmt);
void unregister_quota_format(struct quota_format_type *fmt);
+void init_dquot_operations(struct dquot_operations *fsdqops);
#else
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