| Message ID | 20201208021543.76501-5-laoar.shao@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xfs: avoid transaction reservation recursion | expand |
On Tue, Dec 08, 2020 at 10:15:43AM +0800, Yafang Shao wrote: > - /* > - * Given that we do not allow direct reclaim to call us, we should > - * never be called in a recursive filesystem reclaim context. > - */ > - if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS)) > - goto redirty; > - > /* > * Is this page beyond the end of the file? > * > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 2371187b7615..28db93d0da97 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -568,6 +568,16 @@ xfs_vm_writepage( > { > struct xfs_writepage_ctx wpc = { }; > > + /* > + * Given that we do not allow direct reclaim to call us, we should > + * never be called while in a filesystem transaction. > + */ > + if (xfs_trans_context_active()) { > + redirty_page_for_writepage(wbc, page); > + unlock_page(page); > + return 0; > + } Dave specifically asked for this one to WARN too.
On Tue, Dec 8, 2020 at 10:42 AM Matthew Wilcox <willy@infradead.org> wrote: > > On Tue, Dec 08, 2020 at 10:15:43AM +0800, Yafang Shao wrote: > > - /* > > - * Given that we do not allow direct reclaim to call us, we should > > - * never be called in a recursive filesystem reclaim context. > > - */ > > - if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS)) > > - goto redirty; > > - > > /* > > * Is this page beyond the end of the file? > > * > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > > index 2371187b7615..28db93d0da97 100644 > > --- a/fs/xfs/xfs_aops.c > > +++ b/fs/xfs/xfs_aops.c > > @@ -568,6 +568,16 @@ xfs_vm_writepage( > > { > > struct xfs_writepage_ctx wpc = { }; > > > > + /* > > + * Given that we do not allow direct reclaim to call us, we should > > + * never be called while in a filesystem transaction. > > + */ > > + if (xfs_trans_context_active()) { > > + redirty_page_for_writepage(wbc, page); > > + unlock_page(page); > > + return 0; > > + } > > Dave specifically asked for this one to WARN too. I put the warn in xfs_trans_context_active(), pls. see the definition of it. Is that okay ?
On Tue, Dec 08, 2020 at 10:15:43AM +0800, Yafang Shao wrote: > PF_FSTRANS which is used to avoid transaction reservation recursion, is > dropped since commit 9070733b4efa ("xfs: abstract PF_FSTRANS to > PF_MEMALLOC_NOFS") and commit 7dea19f9ee63 ("mm: introduce > memalloc_nofs_{save,restore} API") and replaced by PF_MEMALLOC_NOFS which > means to avoid filesystem reclaim recursion. > > As these two flags have different meanings, we'd better reintroduce > PF_FSTRANS back. To avoid wasting the space of PF_* flags in task_struct, > we can reuse the current->journal_info to do that, per Willy. As the > check of transaction reservation recursion is used by XFS only, we can > move the check into xfs_vm_writepage(s), per Dave. > > To better abstract that behavoir, two new helpers are introduced, as > follows, > - xfs_trans_context_active > To check whehter current is in fs transcation or not > - xfs_trans_context_swap > Transfer the transaction context when rolling a permanent transaction > > These two new helpers are instroduced in xfs_trans.h. > > Cc: Darrick J. Wong <darrick.wong@oracle.com> > Cc: Matthew Wilcox (Oracle) <willy@infradead.org> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Dave Chinner <david@fromorbit.com> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: David Howells <dhowells@redhat.com> > Cc: Jeff Layton <jlayton@redhat.com> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > --- > fs/iomap/buffered-io.c | 7 ------- > fs/xfs/xfs_aops.c | 17 +++++++++++++++++ > fs/xfs/xfs_trans.c | 3 +++ > fs/xfs/xfs_trans.h | 25 +++++++++++++++++++++++++ > 4 files changed, 45 insertions(+), 7 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 10cc7979ce38..3c53fa6ce64d 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -1458,13 +1458,6 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data) > PF_MEMALLOC)) > goto redirty; > > - /* > - * Given that we do not allow direct reclaim to call us, we should > - * never be called in a recursive filesystem reclaim context. > - */ > - if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS)) > - goto redirty; > - > /* > * Is this page beyond the end of the file? > * > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 2371187b7615..28db93d0da97 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -568,6 +568,16 @@ xfs_vm_writepage( > { > struct xfs_writepage_ctx wpc = { }; > > + /* > + * Given that we do not allow direct reclaim to call us, we should > + * never be called while in a filesystem transaction. > + */ > + if (xfs_trans_context_active()) { > + redirty_page_for_writepage(wbc, page); > + unlock_page(page); > + return 0; > + } hmmm. Missing warning.... > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h > index 44b11c64a15e..82c6735e40fc 100644 > --- a/fs/xfs/xfs_trans.h > +++ b/fs/xfs/xfs_trans.h > @@ -268,16 +268,41 @@ xfs_trans_item_relog( > return lip->li_ops->iop_relog(lip, tp); > } > > +static inline bool > +xfs_trans_context_active(void) > +{ > + /* Use journal_info to indicate current is in a transaction */ > + if (WARN_ON_ONCE(current->journal_info != NULL)) > + return true; > + > + return false; > +} Ah, this is wrong. The call sites should be: if (WARN_ON_ONCE(xfs_trans_context_active())) { /* do error handling */ return error_value; } because we might want to use xfs_trans_context_active() to check if we are in a transaction context or not and that should not generate a warning. Also, placing the warning at the call site gives a more accurate indication of which IO path generated the warning.... Cheers, Dave.
On Tue, Dec 8, 2020 at 12:20 PM Dave Chinner <david@fromorbit.com> wrote: > > On Tue, Dec 08, 2020 at 10:15:43AM +0800, Yafang Shao wrote: > > PF_FSTRANS which is used to avoid transaction reservation recursion, is > > dropped since commit 9070733b4efa ("xfs: abstract PF_FSTRANS to > > PF_MEMALLOC_NOFS") and commit 7dea19f9ee63 ("mm: introduce > > memalloc_nofs_{save,restore} API") and replaced by PF_MEMALLOC_NOFS which > > means to avoid filesystem reclaim recursion. > > > > As these two flags have different meanings, we'd better reintroduce > > PF_FSTRANS back. To avoid wasting the space of PF_* flags in task_struct, > > we can reuse the current->journal_info to do that, per Willy. As the > > check of transaction reservation recursion is used by XFS only, we can > > move the check into xfs_vm_writepage(s), per Dave. > > > > To better abstract that behavoir, two new helpers are introduced, as > > follows, > > - xfs_trans_context_active > > To check whehter current is in fs transcation or not > > - xfs_trans_context_swap > > Transfer the transaction context when rolling a permanent transaction > > > > These two new helpers are instroduced in xfs_trans.h. > > > > Cc: Darrick J. Wong <darrick.wong@oracle.com> > > Cc: Matthew Wilcox (Oracle) <willy@infradead.org> > > Cc: Christoph Hellwig <hch@lst.de> > > Cc: Dave Chinner <david@fromorbit.com> > > Cc: Michal Hocko <mhocko@kernel.org> > > Cc: David Howells <dhowells@redhat.com> > > Cc: Jeff Layton <jlayton@redhat.com> > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > > --- > > fs/iomap/buffered-io.c | 7 ------- > > fs/xfs/xfs_aops.c | 17 +++++++++++++++++ > > fs/xfs/xfs_trans.c | 3 +++ > > fs/xfs/xfs_trans.h | 25 +++++++++++++++++++++++++ > > 4 files changed, 45 insertions(+), 7 deletions(-) > > > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > > index 10cc7979ce38..3c53fa6ce64d 100644 > > --- a/fs/iomap/buffered-io.c > > +++ b/fs/iomap/buffered-io.c > > @@ -1458,13 +1458,6 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data) > > PF_MEMALLOC)) > > goto redirty; > > > > - /* > > - * Given that we do not allow direct reclaim to call us, we should > > - * never be called in a recursive filesystem reclaim context. > > - */ > > - if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS)) > > - goto redirty; > > - > > /* > > * Is this page beyond the end of the file? > > * > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > > index 2371187b7615..28db93d0da97 100644 > > --- a/fs/xfs/xfs_aops.c > > +++ b/fs/xfs/xfs_aops.c > > @@ -568,6 +568,16 @@ xfs_vm_writepage( > > { > > struct xfs_writepage_ctx wpc = { }; > > > > + /* > > + * Given that we do not allow direct reclaim to call us, we should > > + * never be called while in a filesystem transaction. > > + */ > > + if (xfs_trans_context_active()) { > > + redirty_page_for_writepage(wbc, page); > > + unlock_page(page); > > + return 0; > > + } > > hmmm. Missing warning.... > > > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h > > index 44b11c64a15e..82c6735e40fc 100644 > > --- a/fs/xfs/xfs_trans.h > > +++ b/fs/xfs/xfs_trans.h > > @@ -268,16 +268,41 @@ xfs_trans_item_relog( > > return lip->li_ops->iop_relog(lip, tp); > > } > > > > +static inline bool > > +xfs_trans_context_active(void) > > +{ > > + /* Use journal_info to indicate current is in a transaction */ > > + if (WARN_ON_ONCE(current->journal_info != NULL)) > > + return true; > > + > > + return false; > > +} > > Ah, this is wrong. The call sites should be: > > if (WARN_ON_ONCE(xfs_trans_context_active())) { > /* do error handling */ > return error_value; > } > > because we might want to use xfs_trans_context_active() to check if > we are in a transaction context or not and that should not generate > a warning. Also, placing the warning at the call site gives a more > accurate indication of which IO path generated the warning.... > Thanks for the explanation. I will update it in the next version.
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 10cc7979ce38..3c53fa6ce64d 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -1458,13 +1458,6 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data) PF_MEMALLOC)) goto redirty; - /* - * Given that we do not allow direct reclaim to call us, we should - * never be called in a recursive filesystem reclaim context. - */ - if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS)) - goto redirty; - /* * Is this page beyond the end of the file? * diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 2371187b7615..28db93d0da97 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -568,6 +568,16 @@ xfs_vm_writepage( { struct xfs_writepage_ctx wpc = { }; + /* + * Given that we do not allow direct reclaim to call us, we should + * never be called while in a filesystem transaction. + */ + if (xfs_trans_context_active()) { + redirty_page_for_writepage(wbc, page); + unlock_page(page); + return 0; + } + return iomap_writepage(page, wbc, &wpc.ctx, &xfs_writeback_ops); } @@ -579,6 +589,13 @@ xfs_vm_writepages( struct xfs_writepage_ctx wpc = { }; xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED); + /* + * Given that we do not allow direct reclaim to call us, we should + * never be called while in a filesystem transaction. + */ + if (xfs_trans_context_active()) + return 0; + return iomap_writepages(mapping, wbc, &wpc.ctx, &xfs_writeback_ops); } diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c index fe20398a214e..08d4916ffb13 100644 --- a/fs/xfs/xfs_trans.c +++ b/fs/xfs/xfs_trans.c @@ -124,6 +124,9 @@ xfs_trans_dup( tp->t_rtx_res = tp->t_rtx_res_used; ntp->t_pflags = tp->t_pflags; + /* Associate the new transaction with this thread. */ + xfs_trans_context_swap(tp, ntp); + /* move deferred ops over to the new tp */ xfs_defer_move(ntp, tp); diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h index 44b11c64a15e..82c6735e40fc 100644 --- a/fs/xfs/xfs_trans.h +++ b/fs/xfs/xfs_trans.h @@ -268,16 +268,41 @@ xfs_trans_item_relog( return lip->li_ops->iop_relog(lip, tp); } +static inline bool +xfs_trans_context_active(void) +{ + /* Use journal_info to indicate current is in a transaction */ + if (WARN_ON_ONCE(current->journal_info != NULL)) + return true; + + return false; +} + static inline void xfs_trans_context_set(struct xfs_trans *tp) { + ASSERT(!current->journal_info); + current->journal_info = tp; tp->t_pflags = memalloc_nofs_save(); } static inline void xfs_trans_context_clear(struct xfs_trans *tp) { + ASSERT(current->journal_info == tp); + current->journal_info = NULL; memalloc_nofs_restore(tp->t_pflags); } +/* + * Transfer the transaction context when rolling a permanent + * transaction. + */ +static inline void +xfs_trans_context_swap(struct xfs_trans *tp, struct xfs_trans *ntp) +{ + ASSERT(current->journal_info == tp); + current->journal_info = ntp; +} + #endif /* __XFS_TRANS_H__ */
PF_FSTRANS which is used to avoid transaction reservation recursion, is dropped since commit 9070733b4efa ("xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS") and commit 7dea19f9ee63 ("mm: introduce memalloc_nofs_{save,restore} API") and replaced by PF_MEMALLOC_NOFS which means to avoid filesystem reclaim recursion. As these two flags have different meanings, we'd better reintroduce PF_FSTRANS back. To avoid wasting the space of PF_* flags in task_struct, we can reuse the current->journal_info to do that, per Willy. As the check of transaction reservation recursion is used by XFS only, we can move the check into xfs_vm_writepage(s), per Dave. To better abstract that behavoir, two new helpers are introduced, as follows, - xfs_trans_context_active To check whehter current is in fs transcation or not - xfs_trans_context_swap Transfer the transaction context when rolling a permanent transaction These two new helpers are instroduced in xfs_trans.h. Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Jeff Layton <jlayton@redhat.com> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> --- fs/iomap/buffered-io.c | 7 ------- fs/xfs/xfs_aops.c | 17 +++++++++++++++++ fs/xfs/xfs_trans.c | 3 +++ fs/xfs/xfs_trans.h | 25 +++++++++++++++++++++++++ 4 files changed, 45 insertions(+), 7 deletions(-)