diff options
| -rw-r--r-- | fs/super.c | 144 | ||||
| -rw-r--r-- | include/linux/fs.h | 18 |
2 files changed, 129 insertions, 33 deletions
diff --git a/fs/super.c b/fs/super.c index d2b026566dea..aa4e5c11ee32 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1467,6 +1467,21 @@ static struct super_block *get_bdev_super(struct block_device *bdev) return sb; } +/** + * fs_bdev_freeze - freeze owning filesystem of block device + * @bdev: block device + * + * Freeze the filesystem that owns this block device if it is still + * active. + * + * A filesystem that owns multiple block devices may be frozen from each + * block device and won't be unfrozen until all block devices are + * unfrozen. Each block device can only freeze the filesystem once as we + * nest freezes for block devices in the block layer. + * + * Return: If the freeze was successful zero is returned. If the freeze + * failed a negative error code is returned. + */ static int fs_bdev_freeze(struct block_device *bdev) { struct super_block *sb; @@ -1479,15 +1494,34 @@ static int fs_bdev_freeze(struct block_device *bdev) return -EINVAL; if (sb->s_op->freeze_super) - error = sb->s_op->freeze_super(sb, FREEZE_HOLDER_USERSPACE); + error = sb->s_op->freeze_super(sb, + FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE); else - error = freeze_super(sb, FREEZE_HOLDER_USERSPACE); + error = freeze_super(sb, + FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE); if (!error) error = sync_blockdev(bdev); deactivate_super(sb); return error; } +/** + * fs_bdev_thaw - thaw owning filesystem of block device + * @bdev: block device + * + * Thaw the filesystem that owns this block device. + * + * A filesystem that owns multiple block devices may be frozen from each + * block device and won't be unfrozen until all block devices are + * unfrozen. Each block device can only freeze the filesystem once as we + * nest freezes for block devices in the block layer. + * + * Return: If the thaw was successful zero is returned. If the thaw + * failed a negative error code is returned. If this function + * returns zero it doesn't mean that the filesystem is unfrozen + * as it may have been frozen multiple times (kernel may hold a + * freeze or might be frozen from other block devices). + */ static int fs_bdev_thaw(struct block_device *bdev) { struct super_block *sb; @@ -1500,9 +1534,11 @@ static int fs_bdev_thaw(struct block_device *bdev) return -EINVAL; if (sb->s_op->thaw_super) - error = sb->s_op->thaw_super(sb, FREEZE_HOLDER_USERSPACE); + error = sb->s_op->thaw_super(sb, + FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE); else - error = thaw_super(sb, FREEZE_HOLDER_USERSPACE); + error = thaw_super(sb, + FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE); deactivate_super(sb); return error; } @@ -1914,6 +1950,47 @@ static int wait_for_partially_frozen(struct super_block *sb) return ret; } +#define FREEZE_HOLDERS (FREEZE_HOLDER_KERNEL | FREEZE_HOLDER_USERSPACE) +#define FREEZE_FLAGS (FREEZE_HOLDERS | FREEZE_MAY_NEST) + +static inline int freeze_inc(struct super_block *sb, enum freeze_holder who) +{ + WARN_ON_ONCE((who & ~FREEZE_FLAGS)); + WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1); + + if (who & FREEZE_HOLDER_KERNEL) + ++sb->s_writers.freeze_kcount; + if (who & FREEZE_HOLDER_USERSPACE) + ++sb->s_writers.freeze_ucount; + return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount; +} + +static inline int freeze_dec(struct super_block *sb, enum freeze_holder who) +{ + WARN_ON_ONCE((who & ~FREEZE_FLAGS)); + WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1); + + if ((who & FREEZE_HOLDER_KERNEL) && sb->s_writers.freeze_kcount) + --sb->s_writers.freeze_kcount; + if ((who & FREEZE_HOLDER_USERSPACE) && sb->s_writers.freeze_ucount) + --sb->s_writers.freeze_ucount; + return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount; +} + +static inline bool may_freeze(struct super_block *sb, enum freeze_holder who) +{ + WARN_ON_ONCE((who & ~FREEZE_FLAGS)); + WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1); + + if (who & FREEZE_HOLDER_KERNEL) + return (who & FREEZE_MAY_NEST) || + sb->s_writers.freeze_kcount == 0; + if (who & FREEZE_HOLDER_USERSPACE) + return (who & FREEZE_MAY_NEST) || + sb->s_writers.freeze_ucount == 0; + return false; +} + /** * freeze_super - lock the filesystem and force it into a consistent state * @sb: the super to lock @@ -1926,6 +2003,7 @@ static int wait_for_partially_frozen(struct super_block *sb) * @who should be: * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs; * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs. + * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed. * * The @who argument distinguishes between the kernel and userspace trying to * freeze the filesystem. Although there cannot be multiple kernel freezes or @@ -1933,6 +2011,13 @@ static int wait_for_partially_frozen(struct super_block *sb) * userspace can both hold a filesystem frozen. The filesystem remains frozen * until there are no kernel or userspace freezes in effect. * + * A filesystem may hold multiple devices and thus a filesystems may be + * frozen through the block layer via multiple block devices. In this + * case the request is marked as being allowed to nest by passing + * FREEZE_MAY_NEST. The filesystem remains frozen until all block + * devices are unfrozen. If multiple freezes are attempted without + * FREEZE_MAY_NEST -EBUSY will be returned. + * * During this function, sb->s_writers.frozen goes through these values: * * SB_UNFROZEN: File system is normal, all writes progress as usual. @@ -1957,6 +2042,9 @@ static int wait_for_partially_frozen(struct super_block *sb) * mostly auxiliary for filesystems to verify they do not modify frozen fs. * * sb->s_writers.frozen is protected by sb->s_umount. + * + * Return: If the freeze was successful zero is returned. If the freeze + * failed a negative error code is returned. */ int freeze_super(struct super_block *sb, enum freeze_holder who) { @@ -1970,20 +2058,13 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) retry: if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) { - if (sb->s_writers.freeze_holders & who) { - deactivate_locked_super(sb); - return -EBUSY; - } - - WARN_ON(sb->s_writers.freeze_holders == 0); - - /* - * Someone else already holds this type of freeze; share the - * freeze and assign the active ref to the freeze. - */ - sb->s_writers.freeze_holders |= who; - super_unlock_excl(sb); - return 0; + if (may_freeze(sb, who)) + ret = !!WARN_ON_ONCE(freeze_inc(sb, who) == 1); + else + ret = -EBUSY; + /* All freezers share a single active reference. */ + deactivate_locked_super(sb); + return ret; } if (sb->s_writers.frozen != SB_UNFROZEN) { @@ -1998,7 +2079,7 @@ retry: if (sb_rdonly(sb)) { /* Nothing to do really... */ - sb->s_writers.freeze_holders |= who; + WARN_ON_ONCE(freeze_inc(sb, who) > 1); sb->s_writers.frozen = SB_FREEZE_COMPLETE; wake_up_var(&sb->s_writers.frozen); super_unlock_excl(sb); @@ -2048,7 +2129,7 @@ retry: * For debugging purposes so that fs can warn if it sees write activity * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super(). */ - sb->s_writers.freeze_holders |= who; + WARN_ON_ONCE(freeze_inc(sb, who) > 1); sb->s_writers.frozen = SB_FREEZE_COMPLETE; wake_up_var(&sb->s_writers.frozen); lockdep_sb_freeze_release(sb); @@ -2069,21 +2150,15 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) goto out_unlock; - if (!(sb->s_writers.freeze_holders & who)) - goto out_unlock; /* - * Freeze is shared with someone else. Release our hold and drop the - * active ref that freeze_super assigned to the freezer. + * All freezers share a single active reference. + * So just unlock in case there are any left. */ - error = 0; - if (sb->s_writers.freeze_holders & ~who) { - sb->s_writers.freeze_holders &= ~who; - goto out_deactivate; - } + if (freeze_dec(sb, who)) + goto out_unlock; if (sb_rdonly(sb)) { - sb->s_writers.freeze_holders &= ~who; sb->s_writers.frozen = SB_UNFROZEN; wake_up_var(&sb->s_writers.frozen); goto out_deactivate; @@ -2094,13 +2169,13 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) if (sb->s_op->unfreeze_fs) { error = sb->s_op->unfreeze_fs(sb); if (error) { - printk(KERN_ERR "VFS:Filesystem thaw failed\n"); + pr_err("VFS: Filesystem thaw failed\n"); + freeze_inc(sb, who); lockdep_sb_freeze_release(sb); goto out_unlock; } } - sb->s_writers.freeze_holders &= ~who; sb->s_writers.frozen = SB_UNFROZEN; wake_up_var(&sb->s_writers.frozen); sb_freeze_unlock(sb, SB_FREEZE_FS); @@ -2124,6 +2199,11 @@ out_unlock: * @who should be: * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs; * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs. + * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed + * + * A filesystem may hold multiple devices and thus a filesystems may + * have been frozen through the block layer via multiple block devices. + * The filesystem remains frozen until all block devices are unfrozen. */ int thaw_super(struct super_block *sb, enum freeze_holder who) { diff --git a/include/linux/fs.h b/include/linux/fs.h index 7dc6c1bf5f55..b2a3f1c61c19 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1185,7 +1185,8 @@ enum { struct sb_writers { unsigned short frozen; /* Is sb frozen? */ - unsigned short freeze_holders; /* Who froze fs? */ + int freeze_kcount; /* How many kernel freeze requests? */ + int freeze_ucount; /* How many userspace freeze requests? */ struct percpu_rw_semaphore rw_sem[SB_FREEZE_LEVELS]; }; @@ -2051,9 +2052,24 @@ extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos, struct file *dst_file, loff_t dst_pos, loff_t len, unsigned int remap_flags); +/** + * enum freeze_holder - holder of the freeze + * @FREEZE_HOLDER_KERNEL: kernel wants to freeze or thaw filesystem + * @FREEZE_HOLDER_USERSPACE: userspace wants to freeze or thaw filesystem + * @FREEZE_MAY_NEST: whether nesting freeze and thaw requests is allowed + * + * Indicate who the owner of the freeze or thaw request is and whether + * the freeze needs to be exclusive or can nest. + * Without @FREEZE_MAY_NEST, multiple freeze and thaw requests from the + * same holder aren't allowed. It is however allowed to hold a single + * @FREEZE_HOLDER_USERSPACE and a single @FREEZE_HOLDER_KERNEL freeze at + * the same time. This is relied upon by some filesystems during online + * repair or similar. + */ enum freeze_holder { FREEZE_HOLDER_KERNEL = (1U << 0), FREEZE_HOLDER_USERSPACE = (1U << 1), + FREEZE_MAY_NEST = (1U << 2), }; struct super_operations { |