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ext4: Fix and simplify s_dirt handling

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The s_dirt flag wasn't completely handled correctly, but it didn't
really matter when journalling was enabled.  It turns out that when
ext4 runs without a journal, we don't clear s_dirt in places where we
should have, with the result that the high-level write_super()
function was writing the superblock when it wasn't necessary.

So we fix this by making ext4_commit_super() clear the s_dirt flag,
and removing many of the other places where s_dirt is manipulated.
When journalling is enabled, the s_dirt flag might be left set more
often, but s_dirt really doesn't matter when journalling is enabled.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2009-04-30 21:24:04 -04:00
parent e2d670523c
commit 7234ab2a55
1 changed files with 3 additions and 11 deletions
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14
fs/ext4/super.c
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@ -3128,7 +3128,6 @@ static int ext4_load_journal(struct super_block *sb,
if (journal_devnum && if (journal_devnum &&
journal_devnum != le32_to_cpu(es->s_journal_dev)) { journal_devnum != le32_to_cpu(es->s_journal_dev)) {
es->s_journal_dev = cpu_to_le32(journal_devnum); es->s_journal_dev = cpu_to_le32(journal_devnum);
sb->s_dirt = 1;
/* Make sure we flush the recovery flag to disk. */ /* Make sure we flush the recovery flag to disk. */
ext4_commit_super(sb, 1); ext4_commit_super(sb, 1);
@ -3168,7 +3167,7 @@ static int ext4_commit_super(struct super_block *sb, int sync)
&EXT4_SB(sb)->s_freeblocks_counter)); &EXT4_SB(sb)->s_freeblocks_counter));
es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive( es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive(
&EXT4_SB(sb)->s_freeinodes_counter)); &EXT4_SB(sb)->s_freeinodes_counter));
sb->s_dirt = 0;
BUFFER_TRACE(sbh, "marking dirty"); BUFFER_TRACE(sbh, "marking dirty");
mark_buffer_dirty(sbh); mark_buffer_dirty(sbh);
if (sync) { if (sync) {
@ -3210,7 +3209,6 @@ static void ext4_mark_recovery_complete(struct super_block *sb,
if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER) && if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER) &&
sb->s_flags & MS_RDONLY) { sb->s_flags & MS_RDONLY) {
EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER); EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
sb->s_dirt = 0;
ext4_commit_super(sb, 1); ext4_commit_super(sb, 1);
} }
unlock_super(sb); unlock_super(sb);
@ -3271,10 +3269,8 @@ int ext4_force_commit(struct super_block *sb)
return 0; return 0;
journal = EXT4_SB(sb)->s_journal; journal = EXT4_SB(sb)->s_journal;
if (journal) { if (journal)
sb->s_dirt = 0;
ret = ext4_journal_force_commit(journal); ret = ext4_journal_force_commit(journal);
}
return ret; return ret;
} }
@ -3282,15 +3278,13 @@ int ext4_force_commit(struct super_block *sb)
/* /*
* Ext4 always journals updates to the superblock itself, so we don't * Ext4 always journals updates to the superblock itself, so we don't
* have to propagate any other updates to the superblock on disk at this * have to propagate any other updates to the superblock on disk at this
* point. (We can probably nuke this function altogether, and remove * point if the journalling is enabled.
* any mention to sb->s_dirt in all of fs/ext4; eventual cleanup...)
*/ */
static void ext4_write_super(struct super_block *sb) static void ext4_write_super(struct super_block *sb)
{ {
if (EXT4_SB(sb)->s_journal) { if (EXT4_SB(sb)->s_journal) {
if (mutex_trylock(&sb->s_lock) != 0) if (mutex_trylock(&sb->s_lock) != 0)
BUG(); BUG();
sb->s_dirt = 0;
} else { } else {
ext4_commit_super(sb, 1); ext4_commit_super(sb, 1);
} }
@ -3302,7 +3296,6 @@ static int ext4_sync_fs(struct super_block *sb, int wait)
tid_t target; tid_t target;
trace_mark(ext4_sync_fs, "dev %s wait %d", sb->s_id, wait); trace_mark(ext4_sync_fs, "dev %s wait %d", sb->s_id, wait);
sb->s_dirt = 0;
if (EXT4_SB(sb)->s_journal) { if (EXT4_SB(sb)->s_journal) {
if (jbd2_journal_start_commit(EXT4_SB(sb)->s_journal, if (jbd2_journal_start_commit(EXT4_SB(sb)->s_journal,
&target)) { &target)) {
@ -3324,7 +3317,6 @@ static int ext4_freeze(struct super_block *sb)
{ {
int error = 0; int error = 0;
journal_t *journal; journal_t *journal;
sb->s_dirt = 0;
if (!(sb->s_flags & MS_RDONLY)) { if (!(sb->s_flags & MS_RDONLY)) {
journal = EXT4_SB(sb)->s_journal; journal = EXT4_SB(sb)->s_journal;