| Message ID | 171035223488.2613863.7583467519759571221.stgit@frogsfrogsfrogs (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [01/29] fsverity: remove hash page spin lock | expand |
On Wed, Mar 13, 2024 at 10:54:39AM -0700, Darrick J. Wong wrote: > From: Andrey Albershteyn <aalbersh@redhat.com> > > For XFS, fsverity's global workqueue is not really suitable due to: > > 1. High priority workqueues are used within XFS to ensure that data > IO completion cannot stall processing of journal IO completions. > Hence using a WQ_HIGHPRI workqueue directly in the user data IO > path is a potential filesystem livelock/deadlock vector. > > 2. The fsverity workqueue is global - it creates a cross-filesystem > contention point. > > This patch adds per-filesystem, per-cpu workqueue for fsverity > work. This allows iomap to add verification work in the read path on > BIO completion. > > Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com> > Reviewed-by: Darrick J. Wong <djwong@kernel.org> > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > --- > fs/super.c | 7 +++++++ > include/linux/fs.h | 2 ++ > include/linux/fsverity.h | 22 ++++++++++++++++++++++ > 3 files changed, 31 insertions(+) > > > diff --git a/fs/super.c b/fs/super.c > index d35e85295489..338d86864200 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -642,6 +642,13 @@ void generic_shutdown_super(struct super_block *sb) > sb->s_dio_done_wq = NULL; > } > > +#ifdef CONFIG_FS_VERITY > + if (sb->s_read_done_wq) { > + destroy_workqueue(sb->s_read_done_wq); > + sb->s_read_done_wq = NULL; > + } > +#endif > + > if (sop->put_super) > sop->put_super(sb); > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index ed5966a70495..9db24a825d94 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1221,6 +1221,8 @@ struct super_block { > #endif > #ifdef CONFIG_FS_VERITY > const struct fsverity_operations *s_vop; > + /* Completion queue for post read verification */ > + struct workqueue_struct *s_read_done_wq; > #endif > #if IS_ENABLED(CONFIG_UNICODE) > struct unicode_map *s_encoding; > diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h > index 0973b521ac5a..45b7c613148a 100644 > --- a/include/linux/fsverity.h > +++ b/include/linux/fsverity.h > @@ -241,6 +241,22 @@ void fsverity_enqueue_verify_work(struct work_struct *work); > void fsverity_invalidate_block(struct inode *inode, > struct fsverity_blockbuf *block); > > +static inline int fsverity_set_ops(struct super_block *sb, > + const struct fsverity_operations *ops) > +{ > + sb->s_vop = ops; > + > + /* Create per-sb workqueue for post read bio verification */ > + struct workqueue_struct *wq = alloc_workqueue( > + "pread/%s", (WQ_FREEZABLE | WQ_MEM_RECLAIM), 0, sb->s_id); Looking at this more closely, why is it that the fsverity_read_queue is unbound and tagged WQ_HIGHPRI, whereas this one is instead FREEZEABLE and MEM_RECLAIM and bound? If it's really feasible to use /one/ workqueue for all the read post-processing then this ought to be a fs/super.c helper ala sb_init_dio_done_wq. That said, from Eric's comments on the v5 thread about fsverity and fscrypt locking horns over workqueue stalls I'm not convinced that's true. --D > + if (!wq) > + return -ENOMEM; > + > + sb->s_read_done_wq = wq; > + > + return 0; > +} > + > #else /* !CONFIG_FS_VERITY */ > > static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) > @@ -318,6 +334,12 @@ static inline void fsverity_enqueue_verify_work(struct work_struct *work) > WARN_ON_ONCE(1); > } > > +static inline int fsverity_set_ops(struct super_block *sb, > + const struct fsverity_operations *ops) > +{ > + return -EOPNOTSUPP; > +} > + > #endif /* !CONFIG_FS_VERITY */ > > static inline bool fsverity_verify_folio(struct folio *folio) > >
On 2024-03-19 16:30:10, Darrick J. Wong wrote: > On Wed, Mar 13, 2024 at 10:54:39AM -0700, Darrick J. Wong wrote: > > From: Andrey Albershteyn <aalbersh@redhat.com> > > > > For XFS, fsverity's global workqueue is not really suitable due to: > > > > 1. High priority workqueues are used within XFS to ensure that data > > IO completion cannot stall processing of journal IO completions. > > Hence using a WQ_HIGHPRI workqueue directly in the user data IO > > path is a potential filesystem livelock/deadlock vector. > > > > 2. The fsverity workqueue is global - it creates a cross-filesystem > > contention point. > > > > This patch adds per-filesystem, per-cpu workqueue for fsverity > > work. This allows iomap to add verification work in the read path on > > BIO completion. > > > > Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com> > > Reviewed-by: Darrick J. Wong <djwong@kernel.org> > > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > > --- > > fs/super.c | 7 +++++++ > > include/linux/fs.h | 2 ++ > > include/linux/fsverity.h | 22 ++++++++++++++++++++++ > > 3 files changed, 31 insertions(+) > > > > > > diff --git a/fs/super.c b/fs/super.c > > index d35e85295489..338d86864200 100644 > > --- a/fs/super.c > > +++ b/fs/super.c > > @@ -642,6 +642,13 @@ void generic_shutdown_super(struct super_block *sb) > > sb->s_dio_done_wq = NULL; > > } > > > > +#ifdef CONFIG_FS_VERITY > > + if (sb->s_read_done_wq) { > > + destroy_workqueue(sb->s_read_done_wq); > > + sb->s_read_done_wq = NULL; > > + } > > +#endif > > + > > if (sop->put_super) > > sop->put_super(sb); > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index ed5966a70495..9db24a825d94 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -1221,6 +1221,8 @@ struct super_block { > > #endif > > #ifdef CONFIG_FS_VERITY > > const struct fsverity_operations *s_vop; > > + /* Completion queue for post read verification */ > > + struct workqueue_struct *s_read_done_wq; > > #endif > > #if IS_ENABLED(CONFIG_UNICODE) > > struct unicode_map *s_encoding; > > diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h > > index 0973b521ac5a..45b7c613148a 100644 > > --- a/include/linux/fsverity.h > > +++ b/include/linux/fsverity.h > > @@ -241,6 +241,22 @@ void fsverity_enqueue_verify_work(struct work_struct *work); > > void fsverity_invalidate_block(struct inode *inode, > > struct fsverity_blockbuf *block); > > > > +static inline int fsverity_set_ops(struct super_block *sb, > > + const struct fsverity_operations *ops) > > +{ > > + sb->s_vop = ops; > > + > > + /* Create per-sb workqueue for post read bio verification */ > > + struct workqueue_struct *wq = alloc_workqueue( > > + "pread/%s", (WQ_FREEZABLE | WQ_MEM_RECLAIM), 0, sb->s_id); > > Looking at this more closely, why is it that the fsverity_read_queue > is unbound and tagged WQ_HIGHPRI, whereas this one is instead FREEZEABLE > and MEM_RECLAIM and bound? > > If it's really feasible to use /one/ workqueue for all the read > post-processing then this ought to be a fs/super.c helper ala > sb_init_dio_done_wq. That said, from Eric's comments on the v5 thread > about fsverity and fscrypt locking horns over workqueue stalls I'm not > convinced that's true. There's good explanation by Dave why WQ_HIGHPRI is not a good fit for XFS (potential livelock/deadlock): https://lore.kernel.org/linux-xfs/20221214054357.GI3600936@dread.disaster.area/ Based on his feedback I changed it to per-filesystem.
On Wed, Mar 20, 2024 at 11:37:28AM +0100, Andrey Albershteyn wrote: > On 2024-03-19 16:30:10, Darrick J. Wong wrote: > > On Wed, Mar 13, 2024 at 10:54:39AM -0700, Darrick J. Wong wrote: > > > From: Andrey Albershteyn <aalbersh@redhat.com> > > > > > > For XFS, fsverity's global workqueue is not really suitable due to: > > > > > > 1. High priority workqueues are used within XFS to ensure that data > > > IO completion cannot stall processing of journal IO completions. > > > Hence using a WQ_HIGHPRI workqueue directly in the user data IO > > > path is a potential filesystem livelock/deadlock vector. > > > > > > 2. The fsverity workqueue is global - it creates a cross-filesystem > > > contention point. > > > > > > This patch adds per-filesystem, per-cpu workqueue for fsverity > > > work. This allows iomap to add verification work in the read path on > > > BIO completion. > > > > > > Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com> > > > Reviewed-by: Darrick J. Wong <djwong@kernel.org> > > > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > > > --- > > > fs/super.c | 7 +++++++ > > > include/linux/fs.h | 2 ++ > > > include/linux/fsverity.h | 22 ++++++++++++++++++++++ > > > 3 files changed, 31 insertions(+) > > > > > > > > > diff --git a/fs/super.c b/fs/super.c > > > index d35e85295489..338d86864200 100644 > > > --- a/fs/super.c > > > +++ b/fs/super.c > > > @@ -642,6 +642,13 @@ void generic_shutdown_super(struct super_block *sb) > > > sb->s_dio_done_wq = NULL; > > > } > > > > > > +#ifdef CONFIG_FS_VERITY > > > + if (sb->s_read_done_wq) { > > > + destroy_workqueue(sb->s_read_done_wq); > > > + sb->s_read_done_wq = NULL; > > > + } > > > +#endif > > > + > > > if (sop->put_super) > > > sop->put_super(sb); > > > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > > index ed5966a70495..9db24a825d94 100644 > > > --- a/include/linux/fs.h > > > +++ b/include/linux/fs.h > > > @@ -1221,6 +1221,8 @@ struct super_block { > > > #endif > > > #ifdef CONFIG_FS_VERITY > > > const struct fsverity_operations *s_vop; > > > + /* Completion queue for post read verification */ > > > + struct workqueue_struct *s_read_done_wq; > > > #endif > > > #if IS_ENABLED(CONFIG_UNICODE) > > > struct unicode_map *s_encoding; > > > diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h > > > index 0973b521ac5a..45b7c613148a 100644 > > > --- a/include/linux/fsverity.h > > > +++ b/include/linux/fsverity.h > > > @@ -241,6 +241,22 @@ void fsverity_enqueue_verify_work(struct work_struct *work); > > > void fsverity_invalidate_block(struct inode *inode, > > > struct fsverity_blockbuf *block); > > > > > > +static inline int fsverity_set_ops(struct super_block *sb, > > > + const struct fsverity_operations *ops) > > > +{ > > > + sb->s_vop = ops; > > > + > > > + /* Create per-sb workqueue for post read bio verification */ > > > + struct workqueue_struct *wq = alloc_workqueue( > > > + "pread/%s", (WQ_FREEZABLE | WQ_MEM_RECLAIM), 0, sb->s_id); > > > > Looking at this more closely, why is it that the fsverity_read_queue > > is unbound and tagged WQ_HIGHPRI, whereas this one is instead FREEZEABLE > > and MEM_RECLAIM and bound? > > > > If it's really feasible to use /one/ workqueue for all the read > > post-processing then this ought to be a fs/super.c helper ala > > sb_init_dio_done_wq. That said, from Eric's comments on the v5 thread > > about fsverity and fscrypt locking horns over workqueue stalls I'm not > > convinced that's true. > > There's good explanation by Dave why WQ_HIGHPRI is not a good fit > for XFS (potential livelock/deadlock): > > https://lore.kernel.org/linux-xfs/20221214054357.GI3600936@dread.disaster.area/ > > Based on his feedback I changed it to per-filesystem. Ah, ok. Why is the workqueue tagged with MEM_RECLAIM though? Does letting it run actually help out with reclaim? I guess it does by allowing pages involved in readahead to get to unlocked state where they can be ripped out. :) --D > -- > - Andrey > >
On 2024-03-20 07:55:04, Darrick J. Wong wrote: > On Wed, Mar 20, 2024 at 11:37:28AM +0100, Andrey Albershteyn wrote: > > On 2024-03-19 16:30:10, Darrick J. Wong wrote: > > > On Wed, Mar 13, 2024 at 10:54:39AM -0700, Darrick J. Wong wrote: > > > > From: Andrey Albershteyn <aalbersh@redhat.com> > > > > > > > > For XFS, fsverity's global workqueue is not really suitable due to: > > > > > > > > 1. High priority workqueues are used within XFS to ensure that data > > > > IO completion cannot stall processing of journal IO completions. > > > > Hence using a WQ_HIGHPRI workqueue directly in the user data IO > > > > path is a potential filesystem livelock/deadlock vector. > > > > > > > > 2. The fsverity workqueue is global - it creates a cross-filesystem > > > > contention point. > > > > > > > > This patch adds per-filesystem, per-cpu workqueue for fsverity > > > > work. This allows iomap to add verification work in the read path on > > > > BIO completion. > > > > > > > > Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com> > > > > Reviewed-by: Darrick J. Wong <djwong@kernel.org> > > > > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > > > > --- > > > > fs/super.c | 7 +++++++ > > > > include/linux/fs.h | 2 ++ > > > > include/linux/fsverity.h | 22 ++++++++++++++++++++++ > > > > 3 files changed, 31 insertions(+) > > > > > > > > > > > > diff --git a/fs/super.c b/fs/super.c > > > > index d35e85295489..338d86864200 100644 > > > > --- a/fs/super.c > > > > +++ b/fs/super.c > > > > @@ -642,6 +642,13 @@ void generic_shutdown_super(struct super_block *sb) > > > > sb->s_dio_done_wq = NULL; > > > > } > > > > > > > > +#ifdef CONFIG_FS_VERITY > > > > + if (sb->s_read_done_wq) { > > > > + destroy_workqueue(sb->s_read_done_wq); > > > > + sb->s_read_done_wq = NULL; > > > > + } > > > > +#endif > > > > + > > > > if (sop->put_super) > > > > sop->put_super(sb); > > > > > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > > > index ed5966a70495..9db24a825d94 100644 > > > > --- a/include/linux/fs.h > > > > +++ b/include/linux/fs.h > > > > @@ -1221,6 +1221,8 @@ struct super_block { > > > > #endif > > > > #ifdef CONFIG_FS_VERITY > > > > const struct fsverity_operations *s_vop; > > > > + /* Completion queue for post read verification */ > > > > + struct workqueue_struct *s_read_done_wq; > > > > #endif > > > > #if IS_ENABLED(CONFIG_UNICODE) > > > > struct unicode_map *s_encoding; > > > > diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h > > > > index 0973b521ac5a..45b7c613148a 100644 > > > > --- a/include/linux/fsverity.h > > > > +++ b/include/linux/fsverity.h > > > > @@ -241,6 +241,22 @@ void fsverity_enqueue_verify_work(struct work_struct *work); > > > > void fsverity_invalidate_block(struct inode *inode, > > > > struct fsverity_blockbuf *block); > > > > > > > > +static inline int fsverity_set_ops(struct super_block *sb, > > > > + const struct fsverity_operations *ops) > > > > +{ > > > > + sb->s_vop = ops; > > > > + > > > > + /* Create per-sb workqueue for post read bio verification */ > > > > + struct workqueue_struct *wq = alloc_workqueue( > > > > + "pread/%s", (WQ_FREEZABLE | WQ_MEM_RECLAIM), 0, sb->s_id); > > > > > > Looking at this more closely, why is it that the fsverity_read_queue > > > is unbound and tagged WQ_HIGHPRI, whereas this one is instead FREEZEABLE > > > and MEM_RECLAIM and bound? > > > > > > If it's really feasible to use /one/ workqueue for all the read > > > post-processing then this ought to be a fs/super.c helper ala > > > sb_init_dio_done_wq. That said, from Eric's comments on the v5 thread > > > about fsverity and fscrypt locking horns over workqueue stalls I'm not > > > convinced that's true. > > > > There's good explanation by Dave why WQ_HIGHPRI is not a good fit > > for XFS (potential livelock/deadlock): > > > > https://lore.kernel.org/linux-xfs/20221214054357.GI3600936@dread.disaster.area/ > > > > Based on his feedback I changed it to per-filesystem. > > Ah, ok. Why is the workqueue tagged with MEM_RECLAIM though? Does > letting it run actually help out with reclaim? I guess it does by > allowing pages involved in readahead to get to unlocked state where they > can be ripped out. :) Not sure how much it actually helps with reclaims, leaving it out would probably have the same effect in most cases. But I suppose at least one reserved execution context is good thing to not block BIO finalization.
diff --git a/fs/super.c b/fs/super.c index d35e85295489..338d86864200 100644 --- a/fs/super.c +++ b/fs/super.c @@ -642,6 +642,13 @@ void generic_shutdown_super(struct super_block *sb) sb->s_dio_done_wq = NULL; } +#ifdef CONFIG_FS_VERITY + if (sb->s_read_done_wq) { + destroy_workqueue(sb->s_read_done_wq); + sb->s_read_done_wq = NULL; + } +#endif + if (sop->put_super) sop->put_super(sb); diff --git a/include/linux/fs.h b/include/linux/fs.h index ed5966a70495..9db24a825d94 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1221,6 +1221,8 @@ struct super_block { #endif #ifdef CONFIG_FS_VERITY const struct fsverity_operations *s_vop; + /* Completion queue for post read verification */ + struct workqueue_struct *s_read_done_wq; #endif #if IS_ENABLED(CONFIG_UNICODE) struct unicode_map *s_encoding; diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index 0973b521ac5a..45b7c613148a 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -241,6 +241,22 @@ void fsverity_enqueue_verify_work(struct work_struct *work); void fsverity_invalidate_block(struct inode *inode, struct fsverity_blockbuf *block); +static inline int fsverity_set_ops(struct super_block *sb, + const struct fsverity_operations *ops) +{ + sb->s_vop = ops; + + /* Create per-sb workqueue for post read bio verification */ + struct workqueue_struct *wq = alloc_workqueue( + "pread/%s", (WQ_FREEZABLE | WQ_MEM_RECLAIM), 0, sb->s_id); + if (!wq) + return -ENOMEM; + + sb->s_read_done_wq = wq; + + return 0; +} + #else /* !CONFIG_FS_VERITY */ static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) @@ -318,6 +334,12 @@ static inline void fsverity_enqueue_verify_work(struct work_struct *work) WARN_ON_ONCE(1); } +static inline int fsverity_set_ops(struct super_block *sb, + const struct fsverity_operations *ops) +{ + return -EOPNOTSUPP; +} + #endif /* !CONFIG_FS_VERITY */ static inline bool fsverity_verify_folio(struct folio *folio)