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[212.96.48.140]) by smtp.gmail.com with ESMTPSA id v186sm40446906wmb.5.2019.09.03.04.36.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Sep 2019 04:36:44 -0700 (PDT) From: Miklos Szeredi To: virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org Cc: David Howells , linux-kernel@vger.kernel.org, "Michael S. Tsirkin" , Stefan Hajnoczi , Vivek Goyal , "Dr. David Alan Gilbert" , Jens Axboe , linux-block@vger.kernel.org, Al Viro Subject: [PATCH v4 01/16] vfs: Create fs_context-aware mount_bdev() replacement Date: Tue, 3 Sep 2019 13:36:25 +0200 Message-Id: <20190903113640.7984-2-mszeredi@redhat.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190903113640.7984-1-mszeredi@redhat.com> References: <20190903113640.7984-1-mszeredi@redhat.com> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: David Howells Create a function, vfs_get_block_super(), that is fs_context-aware and a replacement for mount_bdev(). It caches the block device pointer and file open mode in the fs_context struct so that this information can be passed into sget_fc()'s test and set functions. Signed-off-by: David Howells cc: Jens Axboe cc: linux-block@vger.kernel.org Signed-off-by: Al Viro --- fs/fs_context.c | 2 + fs/super.c | 111 ++++++++++++++++++++++++++++++++++++- include/linux/fs_context.h | 9 +++ 3 files changed, 121 insertions(+), 1 deletion(-) diff --git a/fs/fs_context.c b/fs/fs_context.c index 103643c68e3f..270ecae32216 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -501,6 +501,8 @@ void put_fs_context(struct fs_context *fc) if (fc->need_free && fc->ops && fc->ops->free) fc->ops->free(fc); + if (fc->dev_destructor) + fc->dev_destructor(fc); security_free_mnt_opts(&fc->security); put_net(fc->net_ns); diff --git a/fs/super.c b/fs/super.c index 5960578a4076..80b56bc7d2db 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1212,6 +1212,110 @@ int get_tree_single(struct fs_context *fc, EXPORT_SYMBOL(get_tree_single); #ifdef CONFIG_BLOCK +static void fc_bdev_destructor(struct fs_context *fc) +{ + if (fc->bdev) { + blkdev_put(fc->bdev, fc->bdev_mode); + fc->bdev = NULL; + } +} + +static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc) +{ + s->s_mode = fc->bdev_mode; + s->s_bdev = fc->bdev; + s->s_dev = s->s_bdev->bd_dev; + s->s_bdi = bdi_get(s->s_bdev->bd_bdi); + fc->bdev = NULL; + return 0; +} + +static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc) +{ + return s->s_bdev == fc->bdev; +} + +/** + * vfs_get_block_super - Get a superblock based on a single block device + * @fc: The filesystem context holding the parameters + * @keying: How to distinguish superblocks + * @fill_super: Helper to initialise a new superblock + */ +int vfs_get_block_super(struct fs_context *fc, + int (*fill_super)(struct super_block *, + struct fs_context *)) +{ + struct block_device *bdev; + struct super_block *s; + int error = 0; + + fc->bdev_mode = FMODE_READ | FMODE_EXCL; + if (!(fc->sb_flags & SB_RDONLY)) + fc->bdev_mode |= FMODE_WRITE; + + if (!fc->source) + return invalf(fc, "No source specified"); + + bdev = blkdev_get_by_path(fc->source, fc->bdev_mode, fc->fs_type); + if (IS_ERR(bdev)) { + errorf(fc, "%s: Can't open blockdev", fc->source); + return PTR_ERR(bdev); + } + + fc->dev_destructor = fc_bdev_destructor; + fc->bdev = bdev; + + /* Once the superblock is inserted into the list by sget_fc(), s_umount + * will protect the lockfs code from trying to start a snapshot while + * we are mounting + */ + mutex_lock(&bdev->bd_fsfreeze_mutex); + if (bdev->bd_fsfreeze_count > 0) { + mutex_unlock(&bdev->bd_fsfreeze_mutex); + warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev); + return -EBUSY; + } + + fc->sb_flags |= SB_NOSEC; + s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc); + mutex_unlock(&bdev->bd_fsfreeze_mutex); + if (IS_ERR(s)) + return PTR_ERR(s); + + if (s->s_root) { + /* Don't summarily change the RO/RW state. */ + if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) { + warnf(fc, "%pg: Can't mount, would change RO state", bdev); + error = -EBUSY; + goto error_sb; + } + + /* Leave fc->bdev to fc_bdev_destructor() to clean up to avoid + * locking conflicts. + */ + } else { + snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); + sb_set_blocksize(s, block_size(bdev)); + error = fill_super(s, fc); + if (error) + goto error_sb; + + s->s_flags |= SB_ACTIVE; + bdev->bd_super = s; + } + + BUG_ON(fc->root); + fc->root = dget(s->s_root); + return 0; + +error_sb: + deactivate_locked_super(s); + /* Leave fc->bdev to fc_bdev_destructor() to clean up */ + return error; +} +EXPORT_SYMBOL(vfs_get_block_super); + + static int set_bdev_super(struct super_block *s, void *data) { s->s_bdev = data; @@ -1411,8 +1515,13 @@ int vfs_get_tree(struct fs_context *fc) * on the superblock. */ error = fc->ops->get_tree(fc); - if (error < 0) + if (error < 0) { + if (fc->dev_destructor) { + fc->dev_destructor(fc); + fc->dev_destructor = NULL; + } return error; + } if (!fc->root) { pr_err("Filesystem %s get_tree() didn't set fc->root\n", diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index 7c6fe3d47fa6..ed5b4349671e 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -88,6 +88,9 @@ struct fs_context { struct mutex uapi_mutex; /* Userspace access mutex */ struct file_system_type *fs_type; void *fs_private; /* The filesystem's context */ + union { + struct block_device *bdev; /* The backing blockdev (if applicable) */ + }; struct dentry *root; /* The root and superblock */ struct user_namespace *user_ns; /* The user namespace for this mount */ struct net *net_ns; /* The network namespace for this mount */ @@ -97,6 +100,7 @@ struct fs_context { const char *subtype; /* The subtype to set on the superblock */ void *security; /* Linux S&M options */ void *s_fs_info; /* Proposed s_fs_info */ + fmode_t bdev_mode; /* File open mode for bdev */ unsigned int sb_flags; /* Proposed superblock flags (SB_*) */ unsigned int sb_flags_mask; /* Superblock flags that were changed */ unsigned int s_iflags; /* OR'd with sb->s_iflags */ @@ -105,6 +109,7 @@ struct fs_context { enum fs_context_phase phase:8; /* The phase the context is in */ bool need_free:1; /* Need to call ops->free() */ bool global:1; /* Goes into &init_user_ns */ + void (*dev_destructor)(struct fs_context *fc); /* For block or mtd */ }; struct fs_context_operations { @@ -154,6 +159,10 @@ extern int get_tree_single(struct fs_context *fc, int (*fill_super)(struct super_block *sb, struct fs_context *fc)); +extern int vfs_get_block_super(struct fs_context *fc, + int (*fill_super)(struct super_block *sb, + struct fs_context *fc)); + extern const struct file_operations fscontext_fops; /*