diff options
author | Christian Brauner <brauner@kernel.org> | 2023-08-23 13:06:55 +0200 |
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committer | Christian Brauner <brauner@kernel.org> | 2023-08-23 13:06:55 +0200 |
commit | 3fb5a6562adef115d8a8c3e19cc9d5fae32e93c8 (patch) | |
tree | 7a0cc61be2ba75aab26403f330da3140424b6b76 /fs/super.c | |
parent | super: use higher-level helper for {freeze,thaw} (diff) | |
parent | fs: wait for partially frozen filesystems (diff) | |
download | linux-3fb5a6562adef115d8a8c3e19cc9d5fae32e93c8.tar.xz linux-3fb5a6562adef115d8a8c3e19cc9d5fae32e93c8.zip |
Merge tag 'vfs-6.6-merge-2' of ssh://gitolite.kernel.org/pub/scm/fs/xfs/xfs-linux
Pull filesystem freezing updates from Darrick Wong:
New code for 6.6:
* Allow the kernel to initiate a freeze of a filesystem. The kernel
and userspace can both hold a freeze on a filesystem at the same
time; the freeze is not lifted until /both/ holders lift it. This
will enable us to fix a longstanding bug in XFS online fsck.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Message-Id: <20230822182604.GB11286@frogsfrogsfrogs>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/super.c')
-rw-r--r-- | fs/super.c | 120 |
1 files changed, 102 insertions, 18 deletions
diff --git a/fs/super.c b/fs/super.c index a284052ebab2..ef87103e2a51 100644 --- a/fs/super.c +++ b/fs/super.c @@ -39,7 +39,7 @@ #include <uapi/linux/mount.h> #include "internal.h" -static int thaw_super_locked(struct super_block *sb); +static int thaw_super_locked(struct super_block *sb, enum freeze_holder who); static LIST_HEAD(super_blocks); static DEFINE_SPINLOCK(sb_lock); @@ -1182,7 +1182,7 @@ static void do_thaw_all_callback(struct super_block *sb) if (born && sb->s_root) { emergency_thaw_bdev(sb); - thaw_super_locked(sb); + thaw_super_locked(sb, FREEZE_HOLDER_USERSPACE); } else { super_unlock_excl(sb); } @@ -1836,14 +1836,43 @@ static void sb_freeze_unlock(struct super_block *sb, int level) percpu_up_write(sb->s_writers.rw_sem + level); } +static int wait_for_partially_frozen(struct super_block *sb) +{ + int ret = 0; + + do { + unsigned short old = sb->s_writers.frozen; + + up_write(&sb->s_umount); + ret = wait_var_event_killable(&sb->s_writers.frozen, + sb->s_writers.frozen != old); + down_write(&sb->s_umount); + } while (ret == 0 && + sb->s_writers.frozen != SB_UNFROZEN && + sb->s_writers.frozen != SB_FREEZE_COMPLETE); + + return ret; +} + /** * freeze_super - lock the filesystem and force it into a consistent state * @sb: the super to lock + * @who: context that wants to freeze * * Syncs the super to make sure the filesystem is consistent and calls the fs's - * freeze_fs. Subsequent calls to this without first thawing the fs will return + * freeze_fs. Subsequent calls to this without first thawing the fs may return * -EBUSY. * + * @who should be: + * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs; + * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs. + * + * The @who argument distinguishes between the kernel and userspace trying to + * freeze the filesystem. Although there cannot be multiple kernel freezes or + * multiple userspace freezes in effect at any given time, the kernel and + * userspace can both hold a filesystem frozen. The filesystem remains frozen + * until there are no kernel or userspace freezes in effect. + * * During this function, sb->s_writers.frozen goes through these values: * * SB_UNFROZEN: File system is normal, all writes progress as usual. @@ -1869,20 +1898,40 @@ static void sb_freeze_unlock(struct super_block *sb, int level) * * sb->s_writers.frozen is protected by sb->s_umount. */ -int freeze_super(struct super_block *sb) +int freeze_super(struct super_block *sb, enum freeze_holder who) { int ret; - /* Since the caller must already have an active reference... */ atomic_inc(&sb->s_active); - - /* ...@sb definitely can't be dying. */ if (!super_lock_excl(sb)) WARN(1, "Dying superblock while freezing!"); +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 (sb->s_writers.frozen != SB_UNFROZEN) { - deactivate_locked_super(sb); - return -EBUSY; + ret = wait_for_partially_frozen(sb); + if (ret) { + deactivate_locked_super(sb); + return ret; + } + + goto retry; } if (!(sb->s_flags & SB_BORN)) { @@ -1892,7 +1941,9 @@ int freeze_super(struct super_block *sb) if (sb_rdonly(sb)) { /* Nothing to do really... */ + sb->s_writers.freeze_holders |= who; sb->s_writers.frozen = SB_FREEZE_COMPLETE; + wake_up_var(&sb->s_writers.frozen); super_unlock_excl(sb); return 0; } @@ -1901,8 +1952,6 @@ int freeze_super(struct super_block *sb) /* Release s_umount to preserve sb_start_write -> s_umount ordering */ super_unlock_excl(sb); sb_wait_write(sb, SB_FREEZE_WRITE); - - /* We're still holding an active reference. */ if (!super_lock_excl(sb)) WARN(1, "Dying superblock while freezing!"); @@ -1915,6 +1964,7 @@ int freeze_super(struct super_block *sb) if (ret) { sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT); + wake_up_var(&sb->s_writers.frozen); deactivate_locked_super(sb); return ret; } @@ -1930,6 +1980,7 @@ int freeze_super(struct super_block *sb) "VFS:Filesystem freeze failed\n"); sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_FS); + wake_up_var(&sb->s_writers.frozen); deactivate_locked_super(sb); return ret; } @@ -1938,24 +1989,50 @@ int freeze_super(struct super_block *sb) * 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; sb->s_writers.frozen = SB_FREEZE_COMPLETE; + wake_up_var(&sb->s_writers.frozen); lockdep_sb_freeze_release(sb); super_unlock_excl(sb); return 0; } EXPORT_SYMBOL(freeze_super); -static int thaw_super_locked(struct super_block *sb) +/* + * Undoes the effect of a freeze_super_locked call. If the filesystem is + * frozen both by userspace and the kernel, a thaw call from either source + * removes that state without releasing the other state or unlocking the + * filesystem. + */ +static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) { int error; - if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) { + if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) { + if (!(sb->s_writers.freeze_holders & who)) { + super_unlock_excl(sb); + return -EINVAL; + } + + /* + * Freeze is shared with someone else. Release our hold and + * drop the active ref that freeze_super assigned to the + * freezer. + */ + if (sb->s_writers.freeze_holders & ~who) { + sb->s_writers.freeze_holders &= ~who; + deactivate_locked_super(sb); + return 0; + } + } else { super_unlock_excl(sb); return -EINVAL; } 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; } @@ -1964,15 +2041,16 @@ static int thaw_super_locked(struct super_block *sb) if (sb->s_op->unfreeze_fs) { error = sb->s_op->unfreeze_fs(sb); if (error) { - printk(KERN_ERR - "VFS:Filesystem thaw failed\n"); + printk(KERN_ERR "VFS:Filesystem thaw failed\n"); lockdep_sb_freeze_release(sb); super_unlock_excl(sb); return error; } } + 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); out: deactivate_locked_super(sb); @@ -1982,14 +2060,20 @@ out: /** * thaw_super -- unlock filesystem * @sb: the super to thaw + * @who: context that wants to freeze + * + * Unlocks the filesystem and marks it writeable again after freeze_super() + * if there are no remaining freezes on the filesystem. * - * Unlocks the filesystem and marks it writeable again after freeze_super(). + * @who should be: + * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs; + * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs. */ -int thaw_super(struct super_block *sb) +int thaw_super(struct super_block *sb, enum freeze_holder who) { if (!super_lock_excl(sb)) WARN(1, "Dying superblock while thawing!"); - return thaw_super_locked(sb); + return thaw_super_locked(sb, who); } EXPORT_SYMBOL(thaw_super); |