* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
> flush_commit_list() uses ll_rw_block() to commit the pending log blocks.
> ll_rw_block() might sleep, and the bkl was released at this point. Then
> we can also relax the write lock at this point.
>
> [ Impact: release the reiserfs write lock when it is not needed ]
>
> Cc: Jeff Mahoney <jeffm@xxxxxxxx>
> Cc: Chris Mason <chris.mason@xxxxxxxxxx>
> Cc: Alexander Beregalov <a.beregalov@xxxxxxxxx>
> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> ---
> fs/reiserfs/journal.c | 7 +++++--
> 1 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
> index 373d080..b1ebd5a 100644
> --- a/fs/reiserfs/journal.c
> +++ b/fs/reiserfs/journal.c
> @@ -1120,8 +1120,11 @@ static int flush_commit_list(struct super_block *s,
> SB_ONDISK_JOURNAL_SIZE(s);
> tbh = journal_find_get_block(s, bn);
> if (tbh) {
> - if (buffer_dirty(tbh))
> - ll_rw_block(WRITE, 1, &tbh) ;
> + if (buffer_dirty(tbh)) {
> + reiserfs_write_unlock(s);
> + ll_rw_block(WRITE, 1, &tbh);
> + reiserfs_write_lock(s);
> + }
> put_bh(tbh) ;
> }
> }
there's 7 other instances of ll_rw_block():
fs/reiserfs/journal.c- spin_unlock(lock);
fs/reiserfs/journal.c: ll_rw_block(WRITE, 1, &bh);
fs/reiserfs/journal.c- spin_lock(lock);
--
fs/reiserfs/journal.c- reiserfs_write_unlock(s);
fs/reiserfs/journal.c: ll_rw_block(WRITE, 1, &tbh);
fs/reiserfs/journal.c- reiserfs_write_lock(s);
--
fs/reiserfs/journal.c- /* read in the log blocks, memcpy to the corresponding real block */
fs/reiserfs/journal.c: ll_rw_block(READ, get_desc_trans_len(desc), log_blocks);
fs/reiserfs/journal.c- for (i = 0; i < get_desc_trans_len(desc); i++) {
--
fs/reiserfs/journal.c- set_buffer_dirty(real_blocks[i]);
fs/reiserfs/journal.c: ll_rw_block(SWRITE, 1, real_blocks + i);
fs/reiserfs/journal.c- }
--
fs/reiserfs/journal.c- }
fs/reiserfs/journal.c: ll_rw_block(READ, j, bhlist);
fs/reiserfs/journal.c- for (i = 1; i < j; i++)
--
fs/reiserfs/stree.c- if (!buffer_uptodate(bh[j]))
fs/reiserfs/stree.c: ll_rw_block(READA, 1, bh + j);
fs/reiserfs/stree.c- brelse(bh[j]);
--
fs/reiserfs/stree.c- reada_blocks, reada_count);
fs/reiserfs/stree.c: ll_rw_block(READ, 1, &bh);
fs/reiserfs/stree.c- reiserfs_write_unlock(sb);
--
fs/reiserfs/super.c-{
fs/reiserfs/super.c: ll_rw_block(READ, 1, &(SB_BUFFER_WITH_SB(s)));
fs/reiserfs/super.c- reiserfs_write_unlock(s);
in particular the second stree.c one and the super.c has a
write-unlock straight before the lock-drop.
I think the stree.c unlock could be moved to before the
ll_rw_block() call straight away.
The super.c one needs more care: first put &(SB_BUFFER_WITH_SB(s))
into a local variable, then unlock the wite-lock, then call
ll_rw_block(). (This is important because &(SB_BUFFER_WITH_SB(s)) is
global filesystem state that has to be read with the lock held.)
ll_rw_block() generally always has a chance to block (especially on
READ) - so the other places could be converted to drop the
write-lock too. Most seem straightforward - some need similar
local-variable treatment as super.c.
Ingo
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