-------- Original Message --------
Subject: [PATCH 1/6] btrfs: add support for processing pending changes
From: David Sterba <dsterba@xxxxxxx>
To: <linux-btrfs@xxxxxxxxxxxxxxx>
Date: 2014年11月14日 18:33
There are some actions that modify global filesystem state but cannot be
performed at the time of request, but later at the transaction commit
time when the filesystem is in a known state.
For example enabling new incompat features on-the-fly or issuing
transaction commit from unsafe contexts (sysfs handlers).
Signed-off-by: David Sterba <dsterba@xxxxxxx>
---
fs/btrfs/ctree.h | 45 +++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/disk-io.c | 6 ++++++
fs/btrfs/transaction.c | 16 ++++++++++++++++
fs/btrfs/transaction.h | 2 ++
4 files changed, 69 insertions(+)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fe69edda11fb..f30b061ef77d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1402,6 +1402,11 @@ struct btrfs_fs_info {
*/
u64 last_trans_log_full_commit;
unsigned long mount_opt;
+ /*
+ * Track requests for actions that need to be done during transaction
+ * commit (like for some mount options).
+ */
+ unsigned long pending_changes;
unsigned long compress_type:4;
int commit_interval;
/*
@@ -2103,6 +2108,7 @@ struct btrfs_ioctl_defrag_range_args {
#define btrfs_raw_test_opt(o, opt) ((o) & BTRFS_MOUNT_##opt)
#define btrfs_test_opt(root, opt) ((root)->fs_info->mount_opt & \
BTRFS_MOUNT_##opt)
+
#define btrfs_set_and_info(root, opt, fmt, args...) \
{ \
if (!btrfs_test_opt(root, opt)) \
@@ -2118,6 +2124,45 @@ struct btrfs_ioctl_defrag_range_args {
}
/*
+ * Requests for changes that need to be done during transaction commit.
+ *
+ * Internal mount options that are used for special handling of the real
+ * mount options (eg. cannot be set during remount and have to be set during
+ * transaction commit)
+ */
+
+#define btrfs_test_pending(info, opt) \
+ test_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
+#define btrfs_set_pending(info, opt) \
+ set_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
+#define btrfs_clear_pending(info, opt) \
+ clear_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
+
+/*
+ * Helpers for setting pending mount option changes.
+ *
+ * Expects corresponding macros
+ * BTRFS_PENDING_SET_ and CLEAR_ + short mount option name
+ */
+#define btrfs_set_pending_and_info(info, opt, fmt, args...) \
+do { \
+ if (!btrfs_raw_test_opt((info)->mount_opt, opt)) { \
+ btrfs_info((info), fmt, ##args); \
+ btrfs_set_pending((info), SET_##opt); \
+ btrfs_clear_pending((info), CLEAR_##opt); \
+ } \
+} while(0)
+
+#define btrfs_clear_pending_and_info(info, opt, fmt, args...) \
+do { \
+ if (btrfs_raw_test_opt((info)->mount_opt, opt)) { \
+ btrfs_info((info), fmt, ##args); \
+ btrfs_set_pending((info), CLEAR_##opt); \
+ btrfs_clear_pending((info), SET_##opt); \
+ } \
+} while(0)
+
+/*
* Inode flags
*/
#define BTRFS_INODE_NODATASUM (1 << 0)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1bf9f897065d..fd80c0d98421 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2834,6 +2834,12 @@ retry_root_backup:
if (btrfs_test_opt(tree_root, CHANGE_INODE_CACHE))
btrfs_set_opt(tree_root->fs_info->mount_opt, INODE_MAP_CACHE);
+ /*
+ * Mount does not set all options immediatelly, we can do it now and do
+ * not have to wait for transaction commit
+ */
+ btrfs_apply_pending_changes(fs_info);
+
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
if (btrfs_test_opt(tree_root, CHECK_INTEGRITY)) {
ret = btrfsic_mount(tree_root, fs_devices,
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index dcaae3616728..7a4024a55e5c 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1850,6 +1850,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
else
btrfs_clear_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
+ btrfs_apply_pending_changes(root->fs_info);
+
/* commit_fs_roots gets rid of all the tree log roots, it is now
* safe to free the root of tree log roots
*/
@@ -2019,3 +2021,17 @@ int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
return (ret < 0) ? 0 : 1;
}
+
+void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info)
+{
+ unsigned long prev;
+ unsigned long bit;
+
+ prev = cmpxchg(&fs_info->pending_changes, 0, 0);
Another HUGE problem here.
cmpxchg will only change the pending_changes to 0 if it's already 0.
If it not 0, it will not change pending_changes to 0.
So pending_changes will always be non-zero if set_pending....
Thanks,
Qu
+ if (!prev)
+ return;
+
+ if (prev)
+ btrfs_warn(fs_info,
+ "unknown pending changes left 0x%lx, ignoring", prev);
+}
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index d8f40e1a5d2d..75ebcfce9d57 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -170,4 +170,6 @@ int btrfs_wait_marked_extents(struct btrfs_root *root,
int btrfs_transaction_blocked(struct btrfs_fs_info *info);
int btrfs_transaction_in_commit(struct btrfs_fs_info *info);
void btrfs_put_transaction(struct btrfs_transaction *transaction);
+void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info);
+
#endif
--
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