Hey Jan,
This series implements your suggestions for the RFC PATCH v2 set,
which we mostly talked about in cover letter [1] and PATCH 3 [2].
(I added Suggested-by: tags, by the way, for due credit.)
It looks almost good on fstests: zero regressions on data=ordered,
and only one regression in data=journal (generic/347); I'll check.
(That's with ext4; I'll check ocfs2, but it's only a minor change.)
However, there's an issue I have to check with you about, that we
exposed from the original kernel. It's described below, but other
than this I _guess_ this should be close if you don't spot errors.
Thanks!
Mauricio
...
Testing with 'stress-ng --mmap <N> --mmap-file' runs well for days,
but it occasionally hits:
JBD2: Spotted dirty metadata buffer (dev = vdc, blocknr = 74775).
There's a risk of filesystem corruption in case of system crash.
I added dump_stack() in warn_dirty_buffer(), and it usually comes
from jbd2_journal_file_buffer(, BJ_Forget) in the commit function.
When filing from BJ_Shadow to BJ_Forget.. so it possibly happened
while BH_Shadow was still set!
So I instrumented [test_]set_buffer_dirty() macros to dump_stack()
if BH_Shadow is set (i.e. buffer being set dirty during write-out.)
This showed that the occasional BH_Dirty setter with BH_Shadow set
is block_page_mkwrite() in ext4_page_mkwrite(). And it seems right,
because it's called before do_journal_get_write_access() (where we
check for/wait on BH_Shadow.)
ext4_page_mkwrite():
err = block_page_mkwrite(vma, vmf, get_block);
if (!err && ext4_should_journal_data(inode)) {
if (ext4_walk_page_buffers(handle, page_buffers(page), 0,
PAGE_SIZE, NULL, do_journal_get_write_access)) {
The patches didn't directly break this, they only allow this code
to run more often as we disabled an early-return optimization for
the case 'all buffers mapped' in data=journal (question 2 in [1]):
ext4_page_mkwrite():
* Return if we have all the buffers mapped.
...
- if (page_has_buffers(page)) {
+ if (page_has_buffers(page) && !ext4_should_journal_data(inode)) {
In order to confirm it, I built the unpatched v5.9-rc4 kernel, with
just the change to disable that optimization in data=journal -- and
it hit that occasionally too ("JBD2: Spotted dirty metadata buffer".)
I was naive enough to mindlessly try to swap the order of those two
statements, in hopes that do_journal_get_write_access() should wait
for BH_Shadow to clear, and then we just call block_page_mkwrite().
BUT it trips into the BUG() check in page_buffers() in the former.
I still have to dig more about it, but if you have something quick
in mind, I'd appreciate any comments/feedback about it, if it gets
more complex than I can see.
Thanks again!
[1] https://lore.kernel.org/linux-ext4/20200819092735.GI1902@xxxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-ext4/20200821102625.GB3432@xxxxxxxxxxxxxx/
Mauricio Faria de Oliveira (3):
jbd2: introduce/export functions
jbd2_journal_submit|finish_inode_data_buffers()
jbd2, ext4, ocfs2: introduce/use journal callbacks
j_submit|finish_inode_data_buffers()
ext4: data=journal: write-protect pages on
j_submit_inode_data_buffers()
fs/ext4/inode.c | 29 +++++++++++-----
fs/ext4/super.c | 82 ++++++++++++++++++++++++++++++++++++++++++++
fs/jbd2/commit.c | 58 +++++++++++++++++--------------
fs/jbd2/journal.c | 2 ++
fs/ocfs2/super.c | 15 ++++++++
include/linux/jbd2.h | 29 +++++++++++++++-
6 files changed, 181 insertions(+), 34 deletions(-)
--
2.17.1
