AcoSail/kernel_optimize_test
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Btrfs: ensure send always works on roots without orphans

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Move the logic from the snapshot creation ioctl into send. This avoids
doing the transaction commit if send isn't used, and ensures that if
a crash/reboot happens after the transaction commit that created the
snapshot and before the transaction commit that switched the commit
root, send will not get a commit root that differs from the main root
(that has orphan items).

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Filipe Manana 2014-10-21 11:11:41 +01:00 committed by Chris Mason
parent 758eb51e71
commit e5fa8f865b
2 changed files with 49 additions and 29 deletions
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29
fs/btrfs/ioctl.c
View File

@ -717,35 +717,6 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
if (ret)
goto fail;
/*
* If orphan cleanup did remove any orphans, it means the tree was
* modified and therefore the commit root is not the same as the
* current root anymore. This is a problem, because send uses the
* commit root and therefore can see inode items that don't exist
* in the current root anymore, and for example make calls to
* btrfs_iget, which will do tree lookups based on the current root
* and not on the commit root. Those lookups will fail, returning a
* -ESTALE error, and making send fail with that error. So make sure
* a send does not see any orphans we have just removed, and that it
* will see the same inodes regardless of whether a transaction
* commit happened before it started (meaning that the commit root
* will be the same as the current root) or not.
*/
if (readonly && pending_snapshot->snap->node !=
pending_snapshot->snap->commit_root) {
trans = btrfs_join_transaction(pending_snapshot->snap);
if (IS_ERR(trans) && PTR_ERR(trans) != -ENOENT) {
ret = PTR_ERR(trans);
goto fail;
}
if (!IS_ERR(trans)) {
ret = btrfs_commit_transaction(trans,
pending_snapshot->snap);
if (ret)
goto fail;
}
}
inode = btrfs_lookup_dentry(dentry->d_parent->d_inode, dentry);
if (IS_ERR(inode)) {
ret = PTR_ERR(inode);

49
fs/btrfs/send.c
View File

@ -5507,6 +5507,51 @@ static int send_subvol(struct send_ctx *sctx)
return ret;
}
/*
* If orphan cleanup did remove any orphans from a root, it means the tree
* was modified and therefore the commit root is not the same as the current
* root anymore. This is a problem, because send uses the commit root and
* therefore can see inode items that don't exist in the current root anymore,
* and for example make calls to btrfs_iget, which will do tree lookups based
* on the current root and not on the commit root. Those lookups will fail,
* returning a -ESTALE error, and making send fail with that error. So make
* sure a send does not see any orphans we have just removed, and that it will
* see the same inodes regardless of whether a transaction commit happened
* before it started (meaning that the commit root will be the same as the
* current root) or not.
*/
static int ensure_commit_roots_uptodate(struct send_ctx *sctx)
{
int i;
struct btrfs_trans_handle *trans = NULL;
again:
if (sctx->parent_root &&
sctx->parent_root->node != sctx->parent_root->commit_root)
goto commit_trans;
for (i = 0; i < sctx->clone_roots_cnt; i++)
if (sctx->clone_roots[i].root->node !=
sctx->clone_roots[i].root->commit_root)
goto commit_trans;
if (trans)
return btrfs_end_transaction(trans, sctx->send_root);
return 0;
commit_trans:
/* Use any root, all fs roots will get their commit roots updated. */
if (!trans) {
trans = btrfs_join_transaction(sctx->send_root);
if (IS_ERR(trans))
return PTR_ERR(trans);
goto again;
}
return btrfs_commit_transaction(trans, sctx->send_root);
}
static void btrfs_root_dec_send_in_progress(struct btrfs_root* root)
{
spin_lock(&root->root_item_lock);
@ -5728,6 +5773,10 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
NULL);
sort_clone_roots = 1;
ret = ensure_commit_roots_uptodate(sctx);
if (ret)
goto out;
current->journal_info = BTRFS_SEND_TRANS_STUB;
ret = send_subvol(sctx);
current->journal_info = NULL;