From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753068AbeDDVX7 (ORCPT ); Wed, 4 Apr 2018 17:23:59 -0400 Received: from mail-eopbgr00115.outbound.protection.outlook.com ([40.107.0.115]:28046 "EHLO EUR02-AM5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752236AbeDDVX4 (ORCPT ); Wed, 4 Apr 2018 17:23:56 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=avagin@virtuozzo.com; Date: Wed, 4 Apr 2018 14:23:41 -0700 From: Andrei Vagin To: Dan Williams Cc: linux-nvdimm@lists.01.org, Michal Hocko , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Christoph Hellwig , Jan Kara , david@fromorbit.com, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, snitzer@redhat.com Subject: Re: [v8, 11/18] mm, dax: enable filesystems to trigger dev_pagemap ->page_free callbacks Message-ID: <20180404212340.GA12737@outlook.office365.com> 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1;AM4PR08MB0740;7:Yb3D861MxC9I75oUTvatWhgW4+l/bQWxBaEnSr3tI8RC6X7QZE/tgwQqkcHp8N5TDvD1W8AMweW/VXA9T9ZTsszb4bGEA57mCP99iV+invbcvhxuEuRWGinEoehU38U4nhBwKZd1aXV57u8lQVUtXjUPgoCHK9ZHyukW/S+7ZKzVAx9P1WcLC3esxEPvQ+HxnkhRUKLuTJNGo+Sf7YGRkBOrfNkQ4rOP/wX8MMHX0J10MaY8D07PLP7qCMDcbfQZ;20:dzM+THfPsvRplmx5s0Szl+/ZnaTunfC7WdbkZqD/pqluA7/d5qmr1DU2F7xbxYht/8wVmYWnYrDh1IAPfIxMNH/vcbAXQIlXnKuwtunstUz4D9L5kYWTrnCyTr3u4zaf4P3G3D0Vg6xFRR42G7IHsSOspSk4zbB2oxmqpeZ/3R8= X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Apr 2018 21:23:49.4000 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 079761df-6fc2-4dab-0416-08d59a725d38 X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 0bc7f26d-0264-416e-a6fc-8352af79c58f X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM4PR08MB0740 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dan, I catch the following bug on the linux-next 20180404. git bisect brought me to this commit: commit 8e4d1ccc5286d2c3da6515b92323a3529aa64496 (HEAD, refs/bisect/bad) Author: Dan Williams Date: Sat Oct 21 14:41:13 2017 -0700 mm, dax: enable filesystems to trigger dev_pagemap ->page_free callbacks [ 11.278768] BUG: unable to handle kernel NULL pointer dereference at 0000000000000440 [ 11.279999] IP: fs_dax_release+0x5/0x90 [ 11.280587] PGD 0 P4D 0 [ 11.280973] Oops: 0000 [#1] SMP PTI [ 11.281500] Modules linked in: [ 11.281968] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.16.0-rc4-00193-g8e4d1ccc5286 #7 [ 11.283163] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014 [ 11.284418] RIP: 0010:fs_dax_release+0x5/0x90 [ 11.285068] RSP: 0000:ffffb1480062fbd8 EFLAGS: 00010287 [ 11.285845] RAX: 0000000000000001 RBX: ffff9e2cb823c088 RCX: 0000000000000003 [ 11.286896] RDX: 0000000000000000 RSI: ffff9e2cb823c088 RDI: 0000000000000000 [ 11.287980] RBP: ffffb1480062fcd8 R08: 0000000000000001 R09: 0000000000000000 [ 11.289147] R10: ffffb1480062fb20 R11: 0000000000000000 R12: 00000000ffffffea [ 11.290576] R13: 0000000000000000 R14: 0000000000000000 R15: ffff9e2cb823a048 [ 11.291630] FS: 0000000000000000(0000) GS:ffff9e2cbfd00000(0000) knlGS:0000000000000000 [ 11.292781] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 11.293602] CR2: 0000000000000440 CR3: 000000007d21e001 CR4: 00000000003606e0 [ 11.294817] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 11.296827] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 11.298293] Call Trace: [ 11.298728] ext4_fill_super+0x31b/0x39d0 [ 11.299441] ? sget_userns+0x155/0x500 [ 11.300144] ? vsnprintf+0x253/0x4b0 [ 11.301223] ? ext4_calculate_overhead+0x4a0/0x4a0 [ 11.301801] ? snprintf+0x45/0x70 [ 11.302214] ? ext4_calculate_overhead+0x4a0/0x4a0 [ 11.302822] mount_bdev+0x17b/0x1b0 [ 11.303332] mount_fs+0x35/0x150 [ 11.303803] vfs_kern_mount.part.25+0x54/0x150 [ 11.304443] do_mount+0x620/0xd60 [ 11.304935] ? memdup_user+0x3e/0x70 [ 11.305458] SyS_mount+0x80/0xd0 [ 11.305931] mount_block_root+0x105/0x2b7 [ 11.306512] ? SyS_mknod+0x16b/0x1f0 [ 11.307035] ? set_debug_rodata+0x11/0x11 [ 11.307616] prepare_namespace+0x135/0x16b [ 11.308215] kernel_init_freeable+0x271/0x297 [ 11.308838] ? rest_init+0xd0/0xd0 [ 11.309322] kernel_init+0xa/0x110 [ 11.309821] ret_from_fork+0x3a/0x50 [ 11.310347] Code: a5 45 31 ed e8 5d 5e 36 00 eb d7 48 c7 c7 20 48 2f a5 e8 4f 5e 36 00 eb c9 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 <48> 8b 87 40 04 00 00 48 8b 40 18 48 85 c0 74 05 e9 c6 7e 60 00 [ 11.313168] RIP: fs_dax_release+0x5/0x90 RSP: ffffb1480062fbd8 [ 11.313991] CR2: 0000000000000440 [ 11.314475] ---[ end trace 8acbb19b74409665 ]--- On Fri, Mar 30, 2018 at 09:03:08PM -0700, Dan Williams wrote: > 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 > Reviewed-by: "Jérôme Glisse" > Reviewed-by: Christoph Hellwig > Reviewed-by: Jan Kara > Signed-off-by: Dan Williams > --- > 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 | 23 ++++++++++++++--------- > 6 files changed, 43 insertions(+), 36 deletions(-) > > diff --git a/drivers/dax/super.c b/drivers/dax/super.c > index c4cf284dfe1c..7d260f118a39 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 > @@ -579,6 +569,17 @@ 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 06f8dcc52ca6..e6d7351f3379 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 7666c065b96f..6ae20e319bc4 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 39bf464c35f1..315a323729e3 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -952,7 +952,7 @@ 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); > } > > @@ -3398,7 +3398,7 @@ 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; > @@ -4408,7 +4408,7 @@ 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 93588ea3d3d2..ef7dd7148c0b 100644 > --- a/fs/xfs/xfs_super.c > +++ b/fs/xfs/xfs_super.c > @@ -724,7 +724,7 @@ xfs_close_devices( > > xfs_free_buftarg(mp, 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, mp->m_rtdev_targp); > xfs_blkdev_put(rtdev); > - fs_put_dax(dax_rtdev); > + fs_dax_release(dax_rtdev, mp); > } > xfs_free_buftarg(mp, 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, 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 e9d59a6b06e1..a88ff009e2a1 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -32,6 +32,8 @@ 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); > @@ -50,6 +52,12 @@ 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) > { > } > @@ -79,12 +87,8 @@ static inline struct dax_device *fs_dax_get_by_host(const char *host) > return dax_get_by_host(host); > } > > -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); > +struct dax_device *fs_dax_claim_bdev(struct block_device *bdev, void *owner); > +void fs_dax_release(struct dax_device *dax_dev, void *owner); > 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); > @@ -100,13 +104,14 @@ static inline struct dax_device *fs_dax_get_by_host(const char *host) > return NULL; > } > > -static inline void fs_put_dax(struct dax_device *dax_dev) > +static inline struct dax_device *fs_dax_claim_bdev(struct block_device *bdev, > + void *owner) > { > + return NULL; > } > > -static inline struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev) > +static inline void fs_dax_release(struct dax_device *dax_dev, void *owner) > { > - return NULL; > } > > static inline int dax_writeback_mapping_range(struct address_space *mapping,