| Message ID | 20200211135500.40524-3-yi.zhang@huawei.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | jbd2: fix an oops problem | expand |
On Tue 11-02-20 21:55:00, zhangyi (F) wrote: > Commit 904cdbd41d74 ("jbd2: clear dirty flag when revoking a buffer from > an older transaction") set the BH_Freed flag when forgetting a metadata > buffer which belongs to the committing transaction, it indicate the > committing process clear dirty bits when it is done with the buffer. But > it also clear the BH_Mapped flag at the same time, which may trigger > below NULL pointer oops when block_size < PAGE_SIZE. > > rmdir 1 kjournald2 mkdir 2 > jbd2_journal_commit_transaction > commit transaction N > jbd2_journal_forget > set_buffer_freed(bh1) > jbd2_journal_commit_transaction > commit transaction N+1 > ... > clear_buffer_mapped(bh1) > ext4_getblk(bh2 ummapped) > ... > grow_dev_page > init_page_buffers > bh1->b_private=NULL > bh2->b_private=NULL > jbd2_journal_put_journal_head(jh1) > __journal_remove_journal_head(hb1) > jh1 is NULL and trigger oops > > *) Dir entry block bh1 and bh2 belongs to one page, and the bh2 has > already been unmapped. > > For the metadata buffer we forgetting, we should always keep the mapped > flag and clear the dirty flags is enough, so this patch pick out the > these buffers and keep their BH_Mapped flag. > > Fixes: 904cdbd41d74 ("jbd2: clear dirty flag when revoking a buffer from an older transaction") > Signed-off-by: zhangyi (F) <yi.zhang@huawei.com> > --- > fs/jbd2/commit.c | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) > > diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c > index ecc2ea5f1b59..8f6f4ddd8b78 100644 > --- a/fs/jbd2/commit.c > +++ b/fs/jbd2/commit.c > @@ -985,12 +985,24 @@ void jbd2_journal_commit_transaction(journal_t *journal) > * pagesize and it is attached to the last partial page. > */ > if (buffer_freed(bh) && !jh->b_next_transaction) { > + struct address_space *mapping; > + > clear_buffer_freed(bh); > clear_buffer_jbddirty(bh); > - clear_buffer_mapped(bh); > - clear_buffer_new(bh); > - clear_buffer_req(bh); > - bh->b_bdev = NULL; > + /* > + * We can (and need to) unmap buffer only for normal > + * mappings. Block device buffers need to stay mapped > + * all the time. We need to be careful about the check > + * because the data page mapping can get cleared under > + * our hands. > + */ > + mapping = READ_ONCE(bh->b_page->mapping); > + if (!(mapping && sb_is_blkdev_sb(mapping->host->i_sb))) { As I wrote in my other email, we don't have to be that aggressive and this condition could actually be (mapping && !sb_is_blkdev_sb()) but I guess it doesn't really matter. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > + clear_buffer_mapped(bh); > + clear_buffer_new(bh); > + clear_buffer_req(bh); > + bh->b_bdev = NULL; > + } > } > > if (buffer_jbddirty(bh)) { > -- > 2.17.2 >
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index ecc2ea5f1b59..8f6f4ddd8b78 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -985,12 +985,24 @@ void jbd2_journal_commit_transaction(journal_t *journal) * pagesize and it is attached to the last partial page. */ if (buffer_freed(bh) && !jh->b_next_transaction) { + struct address_space *mapping; + clear_buffer_freed(bh); clear_buffer_jbddirty(bh); - clear_buffer_mapped(bh); - clear_buffer_new(bh); - clear_buffer_req(bh); - bh->b_bdev = NULL; + /* + * We can (and need to) unmap buffer only for normal + * mappings. Block device buffers need to stay mapped + * all the time. We need to be careful about the check + * because the data page mapping can get cleared under + * our hands. + */ + mapping = READ_ONCE(bh->b_page->mapping); + if (!(mapping && sb_is_blkdev_sb(mapping->host->i_sb))) { + clear_buffer_mapped(bh); + clear_buffer_new(bh); + clear_buffer_req(bh); + bh->b_bdev = NULL; + } } if (buffer_jbddirty(bh)) {
Commit 904cdbd41d74 ("jbd2: clear dirty flag when revoking a buffer from an older transaction") set the BH_Freed flag when forgetting a metadata buffer which belongs to the committing transaction, it indicate the committing process clear dirty bits when it is done with the buffer. But it also clear the BH_Mapped flag at the same time, which may trigger below NULL pointer oops when block_size < PAGE_SIZE. rmdir 1 kjournald2 mkdir 2 jbd2_journal_commit_transaction commit transaction N jbd2_journal_forget set_buffer_freed(bh1) jbd2_journal_commit_transaction commit transaction N+1 ... clear_buffer_mapped(bh1) ext4_getblk(bh2 ummapped) ... grow_dev_page init_page_buffers bh1->b_private=NULL bh2->b_private=NULL jbd2_journal_put_journal_head(jh1) __journal_remove_journal_head(hb1) jh1 is NULL and trigger oops *) Dir entry block bh1 and bh2 belongs to one page, and the bh2 has already been unmapped. For the metadata buffer we forgetting, we should always keep the mapped flag and clear the dirty flags is enough, so this patch pick out the these buffers and keep their BH_Mapped flag. Fixes: 904cdbd41d74 ("jbd2: clear dirty flag when revoking a buffer from an older transaction") Signed-off-by: zhangyi (F) <yi.zhang@huawei.com> --- fs/jbd2/commit.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)