| Message ID | 1448354851-25405-1-git-send-email-jack@suse.cz |
|---|---|
| State | Accepted, archived |
| Headers | show |
On Tue, Nov 24, 2015 at 09:47:31AM +0100, Jan Kara wrote: > Ted and Namjae have reported that truncated pages don't get timely > reclaimed after being truncated in data=journal mode. The following test > triggers the issue easily: > > for (i = 0; i < 1000; i++) { > pwrite(fd, buf, 1024*1024, 0); > fsync(fd); > fsync(fd); > ftruncate(fd, 0); > } > > The reason is that journal_unmap_buffer() finds that truncated buffers > are not journalled (jh->b_transaction == NULL), they are part of > checkpoint list of a transaction (jh->b_cp_transaction != NULL) and have > been already written out (!buffer_dirty(bh)). We clean such buffers but > we leave them in the checkpoint list. Since checkpoint transaction holds > a reference to the journal head, these buffers cannot be released until > the checkpoint transaction is cleaned up. And at that point we don't > call release_buffer_page() anymore so pages detached from mapping are > lingering in the system waiting for reclaim to find them and free them. > > Fix the problem by removing buffers from transaction checkpoint lists > when journal_unmap_buffer() finds out they don't have to be there > anymore. > > Reported-and-tested-by: Namjae Jeon <namjae.jeon@samsung.com> > Fixes: de1b794130b130e77ffa975bb58cb843744f9ae5 > Signed-off-by: Jan Kara <jack@suse.cz> Thanks, applied. Many thanks to Namjae and Jan for tracking this down!! - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index 89463eee6791..daa1514259e0 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -2152,6 +2152,7 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, if (!buffer_dirty(bh)) { /* bdflush has written it. We can drop it now */ + __jbd2_journal_remove_checkpoint(jh); goto zap_buffer; } @@ -2181,6 +2182,7 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, /* The orphan record's transaction has * committed. We can cleanse this buffer */ clear_buffer_jbddirty(bh); + __jbd2_journal_remove_checkpoint(jh); goto zap_buffer; } }
Ted and Namjae have reported that truncated pages don't get timely reclaimed after being truncated in data=journal mode. The following test triggers the issue easily: for (i = 0; i < 1000; i++) { pwrite(fd, buf, 1024*1024, 0); fsync(fd); fsync(fd); ftruncate(fd, 0); } The reason is that journal_unmap_buffer() finds that truncated buffers are not journalled (jh->b_transaction == NULL), they are part of checkpoint list of a transaction (jh->b_cp_transaction != NULL) and have been already written out (!buffer_dirty(bh)). We clean such buffers but we leave them in the checkpoint list. Since checkpoint transaction holds a reference to the journal head, these buffers cannot be released until the checkpoint transaction is cleaned up. And at that point we don't call release_buffer_page() anymore so pages detached from mapping are lingering in the system waiting for reclaim to find them and free them. Fix the problem by removing buffers from transaction checkpoint lists when journal_unmap_buffer() finds out they don't have to be there anymore. Reported-and-tested-by: Namjae Jeon <namjae.jeon@samsung.com> Fixes: de1b794130b130e77ffa975bb58cb843744f9ae5 Signed-off-by: Jan Kara <jack@suse.cz> --- fs/jbd2/transaction.c | 2 ++ 1 file changed, 2 insertions(+)