Re: [PATCH v9 2/9] mm, dax: enable filesystems to trigger dev_pagemap ->page_free callbacks

In order to resolve collisions between filesystem operations and DMA to DAX mapped pages we need a callback when DMA completes. With a callback we can hold off filesystem operations while DMA is in-flight and then resume those operations when the last put_page() occurs on a DMA page. Recall that the 'struct page' entries for DAX memory are created with devm_memremap_pages(). That routine arranges for the pages to be allocated, but never onlined, so a DAX page is DMA-idle when its reference count reaches one. Also recall that the HMM sub-system added infrastructure to trap the page-idle (2-to-1 reference count) transition of the pages allocated by devm_memremap_pages() and trigger a callback via the 'struct dev_pagemap' associated with the page range. Whereas the HMM callbacks are going to a device driver to manage bounce pages in device-memory in the filesystem-dax case we will call back to filesystem specified callback. Since the callback is not known at devm_memremap_pages() time we arrange for the filesystem to install it at mount time. No functional changes are expected as this only registers a nop handler for the ->page_free() event for device-mapped pages. Cc: Michal Hocko <mhocko(a)suse.com&gt; Reviewed-by: "Jérôme Glisse" <jglisse(a)redhat.com&gt; Reviewed-by: Christoph Hellwig <hch(a)lst.de&gt; Reviewed-by: Jan Kara <jack(a)suse.cz&gt; Signed-off-by: Dan Williams <dan.j.williams(a)intel.com&gt; ---

drivers/dax/super.c | 21 +++++++++++---------- drivers/nvdimm/pmem.c | 3 ++- fs/ext2/super.c | 6 +++--- fs/ext4/super.c | 6 +++--- fs/xfs/xfs_super.c | 20 ++++++++++---------- include/linux/dax.h | 14 ++++++++------ 6 files changed, 37 insertions(+), 33 deletions(-) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index e62a64b9c9fb..e4864f319e16 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -63,16 +63,6 @@ int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size, } EXPORT_SYMBOL(bdev_dax_pgoff); -#if IS_ENABLED(CONFIG_FS_DAX) -struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev) -{ - if (!blk_queue_dax(bdev->bd_queue)) - return NULL; - return fs_dax_get_by_host(bdev->bd_disk->disk_name); -} -EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev); -#endif - /** * __bdev_dax_supported() - Check if the device supports dax for filesystem * @sb: The superblock of the device @@ -575,6 +565,17 @@ struct dax_device *alloc_dax(void *private, const char *__host, } EXPORT_SYMBOL_GPL(alloc_dax); +struct dax_device *alloc_dax_devmap(void *private, const char *host, + const struct dax_operations *ops, struct dev_pagemap *pgmap) +{ + struct dax_device *dax_dev = alloc_dax(private, host, ops); + + if (dax_dev) + dax_dev->pgmap = pgmap; + return dax_dev; +} +EXPORT_SYMBOL_GPL(alloc_dax_devmap); + void put_dax(struct dax_device *dax_dev) { if (!dax_dev) diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 9d714926ecf5..fc1a1ab25e9e 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -408,7 +408,8 @@ static int pmem_attach_disk(struct device *dev, nvdimm_badblocks_populate(nd_region, &pmem->bb, &bb_res); disk->bb = &pmem->bb; - dax_dev = alloc_dax(pmem, disk->disk_name, &pmem_dax_ops); + dax_dev = alloc_dax_devmap(pmem, disk->disk_name, &pmem_dax_ops, + &pmem->pgmap); if (!dax_dev) { put_disk(disk); return -ENOMEM; diff --git a/fs/ext2/super.c b/fs/ext2/super.c index de1694512f1f..421c7d4bed39 100644 --- a/fs/ext2/super.c +++ b/fs/ext2/super.c @@ -172,7 +172,7 @@ static void ext2_put_super (struct super_block * sb) brelse (sbi->s_sbh); sb->s_fs_info = NULL; kfree(sbi->s_blockgroup_lock); - fs_put_dax(sbi->s_daxdev); + fs_dax_release(sbi->s_daxdev, sb); kfree(sbi); } @@ -817,7 +817,7 @@ static unsigned long descriptor_loc(struct super_block *sb, static int ext2_fill_super(struct super_block *sb, void *data, int silent) { - struct dax_device *dax_dev = fs_dax_get_by_bdev(sb->s_bdev); + struct dax_device *dax_dev = fs_dax_claim_bdev(sb->s_bdev, sb); struct buffer_head * bh; struct ext2_sb_info * sbi; struct ext2_super_block * es; @@ -1213,7 +1213,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent) kfree(sbi->s_blockgroup_lock); kfree(sbi); failed: - fs_put_dax(dax_dev); + fs_dax_release(dax_dev, sb); return ret; } diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 185f7e61f4cf..3e5d0f9e8772 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -954,7 +954,7 @@ static void ext4_put_super(struct super_block *sb) if (sbi->s_chksum_driver) crypto_free_shash(sbi->s_chksum_driver); kfree(sbi->s_blockgroup_lock); - fs_put_dax(sbi->s_daxdev); + fs_dax_release(sbi->s_daxdev, sb); kfree(sbi); } @@ -3407,7 +3407,7 @@ static void ext4_set_resv_clusters(struct super_block *sb) static int ext4_fill_super(struct super_block *sb, void *data, int silent) { - struct dax_device *dax_dev = fs_dax_get_by_bdev(sb->s_bdev); + struct dax_device *dax_dev = fs_dax_claim_bdev(sb->s_bdev, sb); char *orig_data = kstrdup(data, GFP_KERNEL); struct buffer_head *bh; struct ext4_super_block *es = NULL; @@ -4429,7 +4429,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) out_free_base: kfree(sbi); kfree(orig_data); - fs_put_dax(dax_dev); + fs_dax_release(dax_dev, sb); return err ? err : ret; } diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index d71424052917..f53f8a47a526 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -724,7 +724,7 @@ xfs_close_devices( xfs_free_buftarg(mp->m_logdev_targp); xfs_blkdev_put(logdev); - fs_put_dax(dax_logdev); + fs_dax_release(dax_logdev, mp); } if (mp->m_rtdev_targp) { struct block_device *rtdev = mp->m_rtdev_targp->bt_bdev; @@ -732,10 +732,10 @@ xfs_close_devices( xfs_free_buftarg(mp->m_rtdev_targp); xfs_blkdev_put(rtdev); - fs_put_dax(dax_rtdev); + fs_dax_release(dax_rtdev, mp); } xfs_free_buftarg(mp->m_ddev_targp); - fs_put_dax(dax_ddev); + fs_dax_release(dax_ddev, mp); } /* @@ -753,9 +753,9 @@ xfs_open_devices( struct xfs_mount *mp) { struct block_device *ddev = mp->m_super->s_bdev; - struct dax_device *dax_ddev = fs_dax_get_by_bdev(ddev); - struct dax_device *dax_logdev = NULL, *dax_rtdev = NULL; + struct dax_device *dax_ddev = fs_dax_claim_bdev(ddev, mp); struct block_device *logdev = NULL, *rtdev = NULL; + struct dax_device *dax_logdev = NULL, *dax_rtdev = NULL; int error; /* @@ -765,7 +765,7 @@ xfs_open_devices( error = xfs_blkdev_get(mp, mp->m_logname, &logdev); if (error) goto out; - dax_logdev = fs_dax_get_by_bdev(logdev); + dax_logdev = fs_dax_claim_bdev(logdev, mp); } if (mp->m_rtname) { @@ -779,7 +779,7 @@ xfs_open_devices( error = -EINVAL; goto out_close_rtdev; } - dax_rtdev = fs_dax_get_by_bdev(rtdev); + dax_rtdev = fs_dax_claim_bdev(rtdev, mp); } /* @@ -813,14 +813,14 @@ xfs_open_devices( xfs_free_buftarg(mp->m_ddev_targp); out_close_rtdev: xfs_blkdev_put(rtdev); - fs_put_dax(dax_rtdev); + fs_dax_release(dax_rtdev, mp); out_close_logdev: if (logdev && logdev != ddev) { xfs_blkdev_put(logdev); - fs_put_dax(dax_logdev); + fs_dax_release(dax_logdev, mp); } out: - fs_put_dax(dax_ddev); + fs_dax_release(dax_ddev, mp); return error; } diff --git a/include/linux/dax.h b/include/linux/dax.h index af02f93c943a..fe322d67856e 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -33,6 +33,8 @@ extern struct attribute_group dax_attribute_group; struct dax_device *dax_get_by_host(const char *host); struct dax_device *alloc_dax(void *private, const char *host, const struct dax_operations *ops); +struct dax_device *alloc_dax_devmap(void *private, const char *host, + const struct dax_operations *ops, struct dev_pagemap *pgmap); void put_dax(struct dax_device *dax_dev); void kill_dax(struct dax_device *dax_dev); void dax_write_cache(struct dax_device *dax_dev, bool wc); @@ -51,6 +53,12 @@ static inline struct dax_device *alloc_dax(void *private, const char *host, */ return NULL; } +static inline struct dax_device *alloc_dax_devmap(void *private, + const char *host, const struct dax_operations *ops, + struct dev_pagemap *pgmap) +{ + return NULL; +} static inline void put_dax(struct dax_device *dax_dev) { } @@ -85,7 +93,6 @@ static inline void fs_put_dax(struct dax_device *dax_dev) put_dax(dax_dev); } -struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev); int dax_writeback_mapping_range(struct address_space *mapping, struct block_device *bdev, struct writeback_control *wbc); struct dax_device *fs_dax_claim(struct dax_device *dax_dev, void *owner); @@ -123,11 +130,6 @@ static inline void fs_put_dax(struct dax_device *dax_dev) { } -static inline struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev) -{ - return NULL; -} - static inline int dax_writeback_mapping_range(struct address_space *mapping, struct block_device *bdev, struct writeback_control *wbc) { _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm(a)lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm