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
......@@ -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;
}
......@@ -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;
......
......@@ -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;
}
......
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