| Message ID | 20210924130959.2695749-3-ruansy.fnst@fujitsu.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | fsdax: introduce fs query to support reflink | expand |
On Fri, Sep 24, 2021 at 09:09:53PM +0800, Shiyang Ruan wrote: > To easily track filesystem from a pmem device, we introduce a holder for > dax_device structure, and also its operation. This holder is used to > remember who is using this dax_device: > - When it is the backend of a filesystem, the holder will be the > superblock of this filesystem. > - When this pmem device is one of the targets in a mapped device, the > holder will be this mapped device. In this case, the mapped device > has its own dax_device and it will follow the first rule. So that we > can finally track to the filesystem we needed. > > The holder and holder_ops will be set when filesystem is being mounted, > or an target device is being activated. > > Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> > --- > drivers/dax/super.c | 59 +++++++++++++++++++++++++++++++++++++++++++++ > include/linux/dax.h | 29 ++++++++++++++++++++++ > 2 files changed, 88 insertions(+) > > diff --git a/drivers/dax/super.c b/drivers/dax/super.c > index 48ce86501d93..7d4a11dcba90 100644 > --- a/drivers/dax/super.c > +++ b/drivers/dax/super.c > @@ -23,7 +23,10 @@ > * @cdev: optional character interface for "device dax" > * @host: optional name for lookups where the device path is not available > * @private: dax driver private data > + * @holder_data: holder of a dax_device: could be filesystem or mapped device > * @flags: state and boolean properties > + * @ops: operations for dax_device > + * @holder_ops: operations for the inner holder > */ > struct dax_device { > struct hlist_node list; > @@ -31,8 +34,10 @@ struct dax_device { > struct cdev cdev; > const char *host; > void *private; > + void *holder_data; > unsigned long flags; > const struct dax_operations *ops; > + const struct dax_holder_operations *holder_ops; > }; > > static dev_t dax_devt; > @@ -374,6 +379,29 @@ int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, > } > EXPORT_SYMBOL_GPL(dax_zero_page_range); > > +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, > + size_t size, int flags) > +{ > + int rc; > + > + dax_read_lock(); > + if (!dax_alive(dax_dev)) { > + rc = -ENXIO; > + goto out; > + } > + > + if (!dax_dev->holder_data) { > + rc = -EOPNOTSUPP; > + goto out; > + } > + > + rc = dax_dev->holder_ops->notify_failure(dax_dev, offset, size, flags); Shouldn't this check if dax_dev->holder_ops != NULL before dereferencing it for the function call? Imagine an implementation that wants to attach a ->notify_failure function to a dax_device, maintains its own lookup table, and decides that it doesn't need to set holder_data. (Or, imagine someone who writes a garbage into holder_data and *boom*) How does the locking work here? If there's a media failure, we'll take dax_rwsem and call ->notify_failure. If the ->notify_failure function wants to access the pmem to handle the error by calling back into the dax code, will that cause nested locking on dax_rwsem? Jumping ahead a bit, I think the rmap btree accesses that the xfs implementation performs can cause xfs_buf(fer) cache IO, which would trigger that if the buffers aren't already in memory, if I'm reading this correctly? > +out: > + dax_read_unlock(); > + return rc; > +} > +EXPORT_SYMBOL_GPL(dax_holder_notify_failure); > + > #ifdef CONFIG_ARCH_HAS_PMEM_API > void arch_wb_cache_pmem(void *addr, size_t size); > void dax_flush(struct dax_device *dax_dev, void *addr, size_t size) > @@ -618,6 +646,37 @@ void put_dax(struct dax_device *dax_dev) > } > EXPORT_SYMBOL_GPL(put_dax); > > +void dax_set_holder(struct dax_device *dax_dev, void *holder, > + const struct dax_holder_operations *ops) > +{ > + dax_write_lock(); > + if (!dax_alive(dax_dev)) { > + dax_write_unlock(); > + return; > + } > + > + dax_dev->holder_data = holder; > + dax_dev->holder_ops = ops; > + dax_write_unlock(); I guess this means that the holder has to detach itself before anyone calls kill_dax, or else a dead dax device ends up with a dangling reference to the holder? > +} > +EXPORT_SYMBOL_GPL(dax_set_holder); > + > +void *dax_get_holder(struct dax_device *dax_dev) > +{ > + void *holder; > + > + dax_read_lock(); > + if (!dax_alive(dax_dev)) { > + dax_read_unlock(); > + return NULL; > + } > + > + holder = dax_dev->holder_data; > + dax_read_unlock(); > + return holder; > +} > +EXPORT_SYMBOL_GPL(dax_get_holder); > + > /** > * inode_dax: convert a public inode into its dax_dev > * @inode: An inode with i_cdev pointing to a dax_dev > diff --git a/include/linux/dax.h b/include/linux/dax.h > index 097b3304f9b9..d273d59723cd 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -38,9 +38,24 @@ struct dax_operations { > int (*zero_page_range)(struct dax_device *, pgoff_t, size_t); > }; > > +struct dax_holder_operations { > + /* > + * notify_failure - notify memory failure into inner holder device > + * @dax_dev: the dax device which contains the holder > + * @offset: offset on this dax device where memory failure occurs > + * @size: length of this memory failure event > + * @flags: action flags for memory failure handler > + */ > + int (*notify_failure)(struct dax_device *dax_dev, loff_t offset, > + size_t size, int flags); Shouldn't size be u64 or something? Let's say that 8GB of your pmem go bad, wouldn't you want a single call? Though I guess the current implementation only goes a single page at a time, doesn't it? > +}; > + > extern struct attribute_group dax_attribute_group; > > #if IS_ENABLED(CONFIG_DAX) > +void dax_set_holder(struct dax_device *dax_dev, void *holder, > + const struct dax_holder_operations *ops); > +void *dax_get_holder(struct dax_device *dax_dev); > struct dax_device *alloc_dax(void *private, const char *host, > const struct dax_operations *ops, unsigned long flags); > void put_dax(struct dax_device *dax_dev); > @@ -70,6 +85,18 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma, > return dax_synchronous(dax_dev); > } > #else > +static inline struct dax_device *dax_get_by_host(const char *host) Not sure why this is being added here? AFAICT none of the patches call this function...? --D > +{ > + return NULL; > +} > +static inline void dax_set_holder(struct dax_device *dax_dev, void *holder, > + const struct dax_holder_operations *ops) > +{ > +} > +static inline void *dax_get_holder(struct dax_device *dax_dev) > +{ > + return NULL; > +} > static inline struct dax_device *alloc_dax(void *private, const char *host, > const struct dax_operations *ops, unsigned long flags) > { > @@ -198,6 +225,8 @@ size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, > size_t bytes, struct iov_iter *i); > int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, > size_t nr_pages); > +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, > + size_t size, int flags); > void dax_flush(struct dax_device *dax_dev, void *addr, size_t size); > > ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter, > -- > 2.33.0 > > >
在 2021/10/15 2:00, Darrick J. Wong 写道: > On Fri, Sep 24, 2021 at 09:09:53PM +0800, Shiyang Ruan wrote: >> To easily track filesystem from a pmem device, we introduce a holder for >> dax_device structure, and also its operation. This holder is used to >> remember who is using this dax_device: >> - When it is the backend of a filesystem, the holder will be the >> superblock of this filesystem. >> - When this pmem device is one of the targets in a mapped device, the >> holder will be this mapped device. In this case, the mapped device >> has its own dax_device and it will follow the first rule. So that we >> can finally track to the filesystem we needed. >> >> The holder and holder_ops will be set when filesystem is being mounted, >> or an target device is being activated. >> >> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> >> --- >> drivers/dax/super.c | 59 +++++++++++++++++++++++++++++++++++++++++++++ >> include/linux/dax.h | 29 ++++++++++++++++++++++ >> 2 files changed, 88 insertions(+) >> >> diff --git a/drivers/dax/super.c b/drivers/dax/super.c >> index 48ce86501d93..7d4a11dcba90 100644 >> --- a/drivers/dax/super.c >> +++ b/drivers/dax/super.c >> @@ -23,7 +23,10 @@ >> * @cdev: optional character interface for "device dax" >> * @host: optional name for lookups where the device path is not available >> * @private: dax driver private data >> + * @holder_data: holder of a dax_device: could be filesystem or mapped device >> * @flags: state and boolean properties >> + * @ops: operations for dax_device >> + * @holder_ops: operations for the inner holder >> */ >> struct dax_device { >> struct hlist_node list; >> @@ -31,8 +34,10 @@ struct dax_device { >> struct cdev cdev; >> const char *host; >> void *private; >> + void *holder_data; >> unsigned long flags; >> const struct dax_operations *ops; >> + const struct dax_holder_operations *holder_ops; >> }; >> >> static dev_t dax_devt; >> @@ -374,6 +379,29 @@ int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, >> } >> EXPORT_SYMBOL_GPL(dax_zero_page_range); >> >> +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, >> + size_t size, int flags) >> +{ >> + int rc; >> + >> + dax_read_lock(); >> + if (!dax_alive(dax_dev)) { >> + rc = -ENXIO; >> + goto out; >> + } >> + >> + if (!dax_dev->holder_data) { >> + rc = -EOPNOTSUPP; >> + goto out; >> + } >> + >> + rc = dax_dev->holder_ops->notify_failure(dax_dev, offset, size, flags); > > Shouldn't this check if dax_dev->holder_ops != NULL before dereferencing > it for the function call? Imagine an implementation that wants to > attach a ->notify_failure function to a dax_device, maintains its own > lookup table, and decides that it doesn't need to set holder_data. > > (Or, imagine someone who writes a garbage into holder_data and *boom*) My mistake. I should check @holder_ops instead of @holder_data. > > How does the locking work here? If there's a media failure, we'll take > dax_rwsem and call ->notify_failure. If the ->notify_failure function > wants to access the pmem to handle the error by calling back into the > dax code, will that cause nested locking on dax_rwsem? Won't for now. I have tested it with my simple testcases. > > Jumping ahead a bit, I think the rmap btree accesses that the xfs > implementation performs can cause xfs_buf(fer) cache IO, which would > trigger that if the buffers aren't already in memory, if I'm reading > this correctly? I didn't think of this case. But I think this uses read lock too. It won't be blocked. Only dax_set_holder() takes write lock. > >> +out: >> + dax_read_unlock(); >> + return rc; >> +} >> +EXPORT_SYMBOL_GPL(dax_holder_notify_failure); >> + >> #ifdef CONFIG_ARCH_HAS_PMEM_API >> void arch_wb_cache_pmem(void *addr, size_t size); >> void dax_flush(struct dax_device *dax_dev, void *addr, size_t size) >> @@ -618,6 +646,37 @@ void put_dax(struct dax_device *dax_dev) >> } >> EXPORT_SYMBOL_GPL(put_dax); >> >> +void dax_set_holder(struct dax_device *dax_dev, void *holder, >> + const struct dax_holder_operations *ops) >> +{ >> + dax_write_lock(); >> + if (!dax_alive(dax_dev)) { >> + dax_write_unlock(); >> + return; >> + } >> + >> + dax_dev->holder_data = holder; >> + dax_dev->holder_ops = ops; >> + dax_write_unlock(); > > I guess this means that the holder has to detach itself before anyone > calls kill_dax, or else a dead dax device ends up with a dangling > reference to the holder? Yes. > >> +} >> +EXPORT_SYMBOL_GPL(dax_set_holder); >> + >> +void *dax_get_holder(struct dax_device *dax_dev) >> +{ >> + void *holder; >> + >> + dax_read_lock(); >> + if (!dax_alive(dax_dev)) { >> + dax_read_unlock(); >> + return NULL; >> + } >> + >> + holder = dax_dev->holder_data; >> + dax_read_unlock(); >> + return holder; >> +} >> +EXPORT_SYMBOL_GPL(dax_get_holder); >> + >> /** >> * inode_dax: convert a public inode into its dax_dev >> * @inode: An inode with i_cdev pointing to a dax_dev >> diff --git a/include/linux/dax.h b/include/linux/dax.h >> index 097b3304f9b9..d273d59723cd 100644 >> --- a/include/linux/dax.h >> +++ b/include/linux/dax.h >> @@ -38,9 +38,24 @@ struct dax_operations { >> int (*zero_page_range)(struct dax_device *, pgoff_t, size_t); >> }; >> >> +struct dax_holder_operations { >> + /* >> + * notify_failure - notify memory failure into inner holder device >> + * @dax_dev: the dax device which contains the holder >> + * @offset: offset on this dax device where memory failure occurs >> + * @size: length of this memory failure event >> + * @flags: action flags for memory failure handler >> + */ >> + int (*notify_failure)(struct dax_device *dax_dev, loff_t offset, >> + size_t size, int flags); > > Shouldn't size be u64 or something? Let's say that 8GB of your pmem go > bad, wouldn't you want a single call? Though I guess the current > implementation only goes a single page at a time, doesn't it? Right. > >> +}; >> + >> extern struct attribute_group dax_attribute_group; >> >> #if IS_ENABLED(CONFIG_DAX) >> +void dax_set_holder(struct dax_device *dax_dev, void *holder, >> + const struct dax_holder_operations *ops); >> +void *dax_get_holder(struct dax_device *dax_dev); >> struct dax_device *alloc_dax(void *private, const char *host, >> const struct dax_operations *ops, unsigned long flags); >> void put_dax(struct dax_device *dax_dev); >> @@ -70,6 +85,18 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma, >> return dax_synchronous(dax_dev); >> } >> #else >> +static inline struct dax_device *dax_get_by_host(const char *host) > > Not sure why this is being added here? AFAICT none of the patches call > this function...? It's mistake when I rebase my code to the latest. These lines were deleted but I didn't notice. Will fix it. -- Thanks, Ruan. > > --D > >> +{ >> + return NULL; >> +} >> +static inline void dax_set_holder(struct dax_device *dax_dev, void *holder, >> + const struct dax_holder_operations *ops) >> +{ >> +} >> +static inline void *dax_get_holder(struct dax_device *dax_dev) >> +{ >> + return NULL; >> +} >> static inline struct dax_device *alloc_dax(void *private, const char *host, >> const struct dax_operations *ops, unsigned long flags) >> { >> @@ -198,6 +225,8 @@ size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, >> size_t bytes, struct iov_iter *i); >> int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, >> size_t nr_pages); >> +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, >> + size_t size, int flags); >> void dax_flush(struct dax_device *dax_dev, void *addr, size_t size); >> >> ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter, >> -- >> 2.33.0 >> >> >>
diff --git a/drivers/dax/super.c b/drivers/dax/super.c index 48ce86501d93..7d4a11dcba90 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -23,7 +23,10 @@ * @cdev: optional character interface for "device dax" * @host: optional name for lookups where the device path is not available * @private: dax driver private data + * @holder_data: holder of a dax_device: could be filesystem or mapped device * @flags: state and boolean properties + * @ops: operations for dax_device + * @holder_ops: operations for the inner holder */ struct dax_device { struct hlist_node list; @@ -31,8 +34,10 @@ struct dax_device { struct cdev cdev; const char *host; void *private; + void *holder_data; unsigned long flags; const struct dax_operations *ops; + const struct dax_holder_operations *holder_ops; }; static dev_t dax_devt; @@ -374,6 +379,29 @@ int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, } EXPORT_SYMBOL_GPL(dax_zero_page_range); +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, + size_t size, int flags) +{ + int rc; + + dax_read_lock(); + if (!dax_alive(dax_dev)) { + rc = -ENXIO; + goto out; + } + + if (!dax_dev->holder_data) { + rc = -EOPNOTSUPP; + goto out; + } + + rc = dax_dev->holder_ops->notify_failure(dax_dev, offset, size, flags); +out: + dax_read_unlock(); + return rc; +} +EXPORT_SYMBOL_GPL(dax_holder_notify_failure); + #ifdef CONFIG_ARCH_HAS_PMEM_API void arch_wb_cache_pmem(void *addr, size_t size); void dax_flush(struct dax_device *dax_dev, void *addr, size_t size) @@ -618,6 +646,37 @@ void put_dax(struct dax_device *dax_dev) } EXPORT_SYMBOL_GPL(put_dax); +void dax_set_holder(struct dax_device *dax_dev, void *holder, + const struct dax_holder_operations *ops) +{ + dax_write_lock(); + if (!dax_alive(dax_dev)) { + dax_write_unlock(); + return; + } + + dax_dev->holder_data = holder; + dax_dev->holder_ops = ops; + dax_write_unlock(); +} +EXPORT_SYMBOL_GPL(dax_set_holder); + +void *dax_get_holder(struct dax_device *dax_dev) +{ + void *holder; + + dax_read_lock(); + if (!dax_alive(dax_dev)) { + dax_read_unlock(); + return NULL; + } + + holder = dax_dev->holder_data; + dax_read_unlock(); + return holder; +} +EXPORT_SYMBOL_GPL(dax_get_holder); + /** * inode_dax: convert a public inode into its dax_dev * @inode: An inode with i_cdev pointing to a dax_dev diff --git a/include/linux/dax.h b/include/linux/dax.h index 097b3304f9b9..d273d59723cd 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -38,9 +38,24 @@ struct dax_operations { int (*zero_page_range)(struct dax_device *, pgoff_t, size_t); }; +struct dax_holder_operations { + /* + * notify_failure - notify memory failure into inner holder device + * @dax_dev: the dax device which contains the holder + * @offset: offset on this dax device where memory failure occurs + * @size: length of this memory failure event + * @flags: action flags for memory failure handler + */ + int (*notify_failure)(struct dax_device *dax_dev, loff_t offset, + size_t size, int flags); +}; + extern struct attribute_group dax_attribute_group; #if IS_ENABLED(CONFIG_DAX) +void dax_set_holder(struct dax_device *dax_dev, void *holder, + const struct dax_holder_operations *ops); +void *dax_get_holder(struct dax_device *dax_dev); struct dax_device *alloc_dax(void *private, const char *host, const struct dax_operations *ops, unsigned long flags); void put_dax(struct dax_device *dax_dev); @@ -70,6 +85,18 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma, return dax_synchronous(dax_dev); } #else +static inline struct dax_device *dax_get_by_host(const char *host) +{ + return NULL; +} +static inline void dax_set_holder(struct dax_device *dax_dev, void *holder, + const struct dax_holder_operations *ops) +{ +} +static inline void *dax_get_holder(struct dax_device *dax_dev) +{ + return NULL; +} static inline struct dax_device *alloc_dax(void *private, const char *host, const struct dax_operations *ops, unsigned long flags) { @@ -198,6 +225,8 @@ size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i); int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, size_t nr_pages); +int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset, + size_t size, int flags); void dax_flush(struct dax_device *dax_dev, void *addr, size_t size); ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
To easily track filesystem from a pmem device, we introduce a holder for dax_device structure, and also its operation. This holder is used to remember who is using this dax_device: - When it is the backend of a filesystem, the holder will be the superblock of this filesystem. - When this pmem device is one of the targets in a mapped device, the holder will be this mapped device. In this case, the mapped device has its own dax_device and it will follow the first rule. So that we can finally track to the filesystem we needed. The holder and holder_ops will be set when filesystem is being mounted, or an target device is being activated. Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> --- drivers/dax/super.c | 59 +++++++++++++++++++++++++++++++++++++++++++++ include/linux/dax.h | 29 ++++++++++++++++++++++ 2 files changed, 88 insertions(+)