| Message ID | 20221231150919.659533-3-agruenba@redhat.com |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | Turn iomap_page_ops into iomap_folio_ops | expand |
On Sat, Dec 31, 2022 at 04:09:12PM +0100, Andreas Gruenbacher wrote: > When an iomap defines a ->page_done() handler in its page_ops, delegate > unlocking the folio and putting the folio reference to that handler. > > This allows to fix a race between journaled data writes and folio > writeback in gfs2: before this change, gfs2_iomap_page_done() was called > after unlocking the folio, so writeback could start writing back the > folio's buffers before they could be marked for writing to the journal. > Also, try_to_free_buffers() could free the buffers before > gfs2_iomap_page_done() was done adding the buffers to the current > current transaction. With this change, gfs2_iomap_page_done() adds the > buffers to the current transaction while the folio is still locked, so > the problems described above can no longer occur. > > The only current user of ->page_done() is gfs2, so other filesystems are > not affected. To catch out any out-of-tree users, switch from a page to > a folio in ->page_done(). I really hope there aren't any out of tree users... > Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> --D > --- > fs/gfs2/bmap.c | 15 ++++++++++++--- > fs/iomap/buffered-io.c | 8 ++++---- > include/linux/iomap.h | 7 ++++--- > 3 files changed, 20 insertions(+), 10 deletions(-) > > diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c > index e7537fd305dd..46206286ad42 100644 > --- a/fs/gfs2/bmap.c > +++ b/fs/gfs2/bmap.c > @@ -968,14 +968,23 @@ static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos, > } > > static void gfs2_iomap_page_done(struct inode *inode, loff_t pos, > - unsigned copied, struct page *page) > + unsigned copied, struct folio *folio) > { > struct gfs2_trans *tr = current->journal_info; > struct gfs2_inode *ip = GFS2_I(inode); > struct gfs2_sbd *sdp = GFS2_SB(inode); > > - if (page && !gfs2_is_stuffed(ip)) > - gfs2_page_add_databufs(ip, page, offset_in_page(pos), copied); > + if (!folio) { > + gfs2_trans_end(sdp); > + return; > + } > + > + if (!gfs2_is_stuffed(ip)) > + gfs2_page_add_databufs(ip, &folio->page, offset_in_page(pos), > + copied); > + > + folio_unlock(folio); > + folio_put(folio); > > if (tr->tr_num_buf_new) > __mark_inode_dirty(inode, I_DIRTY_DATASYNC); > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index c30d150a9303..e13d5694e299 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -580,12 +580,12 @@ static void iomap_put_folio(struct iomap_iter *iter, loff_t pos, size_t ret, > { > const struct iomap_page_ops *page_ops = iter->iomap.page_ops; > > - if (folio) > + if (page_ops && page_ops->page_done) { > + page_ops->page_done(iter->inode, pos, ret, folio); > + } else if (folio) { > folio_unlock(folio); > - if (page_ops && page_ops->page_done) > - page_ops->page_done(iter->inode, pos, ret, &folio->page); > - if (folio) > folio_put(folio); > + } > } > > static int iomap_write_begin_inline(const struct iomap_iter *iter, > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 0983dfc9a203..743e2a909162 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -131,13 +131,14 @@ static inline bool iomap_inline_data_valid(const struct iomap *iomap) > * associated with them. > * > * When page_prepare succeeds, page_done will always be called to do any > - * cleanup work necessary. In that page_done call, @page will be NULL if the > - * associated page could not be obtained. > + * cleanup work necessary. In that page_done call, @folio will be NULL if the > + * associated folio could not be obtained. When folio is not NULL, page_done > + * is responsible for unlocking and putting the folio. > */ > struct iomap_page_ops { > int (*page_prepare)(struct inode *inode, loff_t pos, unsigned len); > void (*page_done)(struct inode *inode, loff_t pos, unsigned copied, > - struct page *page); > + struct folio *folio); > > /* > * Check that the cached iomap still maps correctly to the filesystem's > -- > 2.38.1 >
Looks good:
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c index e7537fd305dd..46206286ad42 100644 --- a/fs/gfs2/bmap.c +++ b/fs/gfs2/bmap.c @@ -968,14 +968,23 @@ static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos, } static void gfs2_iomap_page_done(struct inode *inode, loff_t pos, - unsigned copied, struct page *page) + unsigned copied, struct folio *folio) { struct gfs2_trans *tr = current->journal_info; struct gfs2_inode *ip = GFS2_I(inode); struct gfs2_sbd *sdp = GFS2_SB(inode); - if (page && !gfs2_is_stuffed(ip)) - gfs2_page_add_databufs(ip, page, offset_in_page(pos), copied); + if (!folio) { + gfs2_trans_end(sdp); + return; + } + + if (!gfs2_is_stuffed(ip)) + gfs2_page_add_databufs(ip, &folio->page, offset_in_page(pos), + copied); + + folio_unlock(folio); + folio_put(folio); if (tr->tr_num_buf_new) __mark_inode_dirty(inode, I_DIRTY_DATASYNC); diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index c30d150a9303..e13d5694e299 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -580,12 +580,12 @@ static void iomap_put_folio(struct iomap_iter *iter, loff_t pos, size_t ret, { const struct iomap_page_ops *page_ops = iter->iomap.page_ops; - if (folio) + if (page_ops && page_ops->page_done) { + page_ops->page_done(iter->inode, pos, ret, folio); + } else if (folio) { folio_unlock(folio); - if (page_ops && page_ops->page_done) - page_ops->page_done(iter->inode, pos, ret, &folio->page); - if (folio) folio_put(folio); + } } static int iomap_write_begin_inline(const struct iomap_iter *iter, diff --git a/include/linux/iomap.h b/include/linux/iomap.h index 0983dfc9a203..743e2a909162 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -131,13 +131,14 @@ static inline bool iomap_inline_data_valid(const struct iomap *iomap) * associated with them. * * When page_prepare succeeds, page_done will always be called to do any - * cleanup work necessary. In that page_done call, @page will be NULL if the - * associated page could not be obtained. + * cleanup work necessary. In that page_done call, @folio will be NULL if the + * associated folio could not be obtained. When folio is not NULL, page_done + * is responsible for unlocking and putting the folio. */ struct iomap_page_ops { int (*page_prepare)(struct inode *inode, loff_t pos, unsigned len); void (*page_done)(struct inode *inode, loff_t pos, unsigned copied, - struct page *page); + struct folio *folio); /* * Check that the cached iomap still maps correctly to the filesystem's
When an iomap defines a ->page_done() handler in its page_ops, delegate unlocking the folio and putting the folio reference to that handler. This allows to fix a race between journaled data writes and folio writeback in gfs2: before this change, gfs2_iomap_page_done() was called after unlocking the folio, so writeback could start writing back the folio's buffers before they could be marked for writing to the journal. Also, try_to_free_buffers() could free the buffers before gfs2_iomap_page_done() was done adding the buffers to the current current transaction. With this change, gfs2_iomap_page_done() adds the buffers to the current transaction while the folio is still locked, so the problems described above can no longer occur. The only current user of ->page_done() is gfs2, so other filesystems are not affected. To catch out any out-of-tree users, switch from a page to a folio in ->page_done(). Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> --- fs/gfs2/bmap.c | 15 ++++++++++++--- fs/iomap/buffered-io.c | 8 ++++---- include/linux/iomap.h | 7 ++++--- 3 files changed, 20 insertions(+), 10 deletions(-)