Andrew Morton wrote:
On Fri, 04 May 2007 10:18:12 +0400 Alex Tomas <alex@xxxxxxxxxxxxx> wrote:
Andrew Morton wrote:
Yes, there can be issues with needing to allocate journal space within the
context of a commit. But
no-no, this isn't required. we only need to mark pages/blocks within
transaction, otherwise race is possible when we allocate blocks in transaction,
then transacton starts to commit, then we mark pages/blocks to be flushed
before commit.
I don't understand. Can you please describe the race in more detail?
if I understood your idea right, then in data=ordered mode, commit thread writes
all dirty mapped blocks before real commit.
say, we have two threads: t1 is a thread doing flushing and t2 is a commit thread
t1 t2
find dirty inode I
find some dirty unallocated blocks
journal_start()
allocate blocks
attach them to I
journal_stop()
going to commit
find inode I dirty
do NOT find these blocks because they're
allocated only, but pages/bhs aren't mapped
to them
start commit
map pages/bhs to just allocate blocks
so, either we mark pages/bhs someway within journal_start()--journal_stop() or
commit thread should do lookup for all dirty pages. the latter doesn't sound nice, IMHO.
thanks, Alex
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