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Commit 8e8ad8a5 authored by Jan Kara's avatar Jan Kara Committed by Al Viro
Browse files

ext4: Convert to new freezing mechanism 

We remove most of frozen checks since upper layer takes care of blocking all
writes. We have to handle protection in ext4_page_mkwrite() in a special way
because we cannot use generic block_page_mkwrite(). Also we add a freeze
protection to ext4_evict_inode() so that iput() of unlinked inode cannot modify
a frozen filesystem (we cannot easily instrument ext4_journal_start() /
ext4_journal_stop() with freeze protection because we are missing the
superblock pointer in ext4_journal_stop() in nojournal mode).

CC: linux-ext4@vger.kernel.org
CC: "Theodore Ts'o" <tytso@mit.edu>
BugLink: https://bugs.launchpad.net/bugs/897421


Tested-by: default avatarKamal Mostafa <kamal@canonical.com>
Tested-by: default avatarPeter M. Petrakis <peter.petrakis@canonical.com>
Tested-by: default avatarDann Frazier <dann.frazier@canonical.com>
Tested-by: default avatarMassimo Morana <massimo.morana@canonical.com>
Acked-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 14da9200

fs/ext4/inode.c

+10 −5
Original line number Diff line number Diff line
@@ -233,6 +233,11 @@ void ext4_evict_inode(struct inode *inode) 
	if (is_bad_inode(inode))

		goto no_delete;



	/*

	 * Protect us against freezing - iput() caller didn't have to have any

	 * protection against it

	 */

	sb_start_intwrite(inode->i_sb);

	handle = ext4_journal_start(inode, ext4_blocks_for_truncate(inode)+3);

	if (IS_ERR(handle)) {

		ext4_std_error(inode->i_sb, PTR_ERR(handle));
@@ -242,6 +247,7 @@ void ext4_evict_inode(struct inode *inode) 
		 * cleaned up.

		 */

		ext4_orphan_del(NULL, inode);

		sb_end_intwrite(inode->i_sb);

		goto no_delete;

	}
@@ -273,6 +279,7 @@ void ext4_evict_inode(struct inode *inode) 
		stop_handle:

			ext4_journal_stop(handle);

			ext4_orphan_del(NULL, inode);

			sb_end_intwrite(inode->i_sb);

			goto no_delete;

		}

	}
@@ -301,6 +308,7 @@ void ext4_evict_inode(struct inode *inode) 
	else

		ext4_free_inode(handle, inode);

	ext4_journal_stop(handle);

	sb_end_intwrite(inode->i_sb);

	return;

no_delete:

	ext4_clear_inode(inode);	/* We must guarantee clearing of inode... */
@@ -4701,11 +4709,7 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) 
	get_block_t *get_block;

	int retries = 0;



	/*

	 * This check is racy but catches the common case. We rely on

	 * __block_page_mkwrite() to do a reliable check.

	 */

	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

	sb_start_pagefault(inode->i_sb);

	/* Delalloc case is easy... */

	if (test_opt(inode->i_sb, DELALLOC) &&

	    !ext4_should_journal_data(inode) &&
@@ -4773,5 +4777,6 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) 
out_ret:

	ret = block_page_mkwrite_return(ret);

out:

	sb_end_pagefault(inode->i_sb);

	return ret;

}

fs/ext4/mmp.c

+6 −0
Original line number Diff line number Diff line
@@ -44,6 +44,11 @@ static int write_mmp_block(struct super_block *sb, struct buffer_head *bh) 
{

	struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);



	/*

	 * We protect against freezing so that we don't create dirty buffers

	 * on frozen filesystem.

	 */

	sb_start_write(sb);

	ext4_mmp_csum_set(sb, mmp);

	mark_buffer_dirty(bh);

	lock_buffer(bh);
@@ -51,6 +56,7 @@ static int write_mmp_block(struct super_block *sb, struct buffer_head *bh) 
	get_bh(bh);

	submit_bh(WRITE_SYNC, bh);

	wait_on_buffer(bh);

	sb_end_write(sb);

	if (unlikely(!buffer_uptodate(bh)))

		return 1;

fs/ext4/super.c

+7 −24
Original line number Diff line number Diff line
@@ -332,33 +332,17 @@ static void ext4_put_nojournal(handle_t *handle) 
 * journal_end calls result in the superblock being marked dirty, so

 * that sync() will call the filesystem's write_super callback if

 * appropriate.

 *

 * To avoid j_barrier hold in userspace when a user calls freeze(),

 * ext4 prevents a new handle from being started by s_frozen, which

 * is in an upper layer.

 */

handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks)

{

	journal_t *journal;

	handle_t  *handle;



	trace_ext4_journal_start(sb, nblocks, _RET_IP_);

	if (sb->s_flags & MS_RDONLY)

		return ERR_PTR(-EROFS);



	WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);

	journal = EXT4_SB(sb)->s_journal;

	handle = ext4_journal_current_handle();



	/*

	 * If a handle has been started, it should be allowed to

	 * finish, otherwise deadlock could happen between freeze

	 * and others(e.g. truncate) due to the restart of the

	 * journal handle if the filesystem is forzen and active

	 * handles are not stopped.

	 */

	if (!handle)

		vfs_check_frozen(sb, SB_FREEZE_TRANS);



	if (!journal)

		return ext4_get_nojournal();

	/*
@@ -2723,6 +2707,7 @@ static int ext4_run_li_request(struct ext4_li_request *elr) 
	sb = elr->lr_super;

	ngroups = EXT4_SB(sb)->s_groups_count;



	sb_start_write(sb);

	for (group = elr->lr_next_group; group < ngroups; group++) {

		gdp = ext4_get_group_desc(sb, group, NULL);

		if (!gdp) {
@@ -2749,6 +2734,7 @@ static int ext4_run_li_request(struct ext4_li_request *elr) 
		elr->lr_next_sched = jiffies + elr->lr_timeout;

		elr->lr_next_group = group + 1;

	}

	sb_end_write(sb);



	return ret;

}
@@ -4302,10 +4288,8 @@ int ext4_force_commit(struct super_block *sb) 
		return 0;



	journal = EXT4_SB(sb)->s_journal;

	if (journal) {

		vfs_check_frozen(sb, SB_FREEZE_TRANS);

	if (journal)

		ret = ext4_journal_force_commit(journal);

	}



	return ret;

}
@@ -4342,9 +4326,8 @@ static int ext4_sync_fs(struct super_block *sb, int wait) 
 * gives us a chance to flush the journal completely and mark the fs clean.

 *

 * Note that only this function cannot bring a filesystem to be in a clean

 * state independently, because ext4 prevents a new handle from being started

 * by @sb->s_frozen, which stays in an upper layer.  It thus needs help from

 * the upper layer.

 * state independently. It relies on upper layer to stop all data & metadata

 * modifications.

 */

static int ext4_freeze(struct super_block *sb)

{
@@ -4371,7 +4354,7 @@ static int ext4_freeze(struct super_block *sb) 
	EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);

	error = ext4_commit_super(sb, 1);

out:

	/* we rely on s_frozen to stop further updates */

	/* we rely on upper layer to stop further updates */

	jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);

	return error;

}