| Message ID | 20171129232356.28296-2-mcgrof@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed 29-11-17 15:23:46, Luis R. Rodriguez wrote: > freeze_super() holds a write lock, however we wish to also enable > callers which already hold the write lock. To do this provide a helper > and make freeze_super() use it. This way, all that freeze_super() does > now is lock handling and active count management. > > This change has no functional changes. > > Suggested-by: Dave Chinner <david@fromorbit.com> > Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > fs/super.c | 100 +++++++++++++++++++++++++++++++++---------------------------- > 1 file changed, 55 insertions(+), 45 deletions(-) > > diff --git a/fs/super.c b/fs/super.c > index d4e33e8f1e6f..a7650ff22f0e 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -1387,59 +1387,20 @@ static void sb_freeze_unlock(struct super_block *sb) > percpu_up_write(sb->s_writers.rw_sem + level); > } > > -/** > - * freeze_super - lock the filesystem and force it into a consistent state > - * @sb: the super to lock > - * > - * 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 > - * -EBUSY. > - * > - * During this function, sb->s_writers.frozen goes through these values: > - * > - * SB_UNFROZEN: File system is normal, all writes progress as usual. > - * > - * SB_FREEZE_WRITE: The file system is in the process of being frozen. New > - * writes should be blocked, though page faults are still allowed. We wait for > - * all writes to complete and then proceed to the next stage. > - * > - * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked > - * but internal fs threads can still modify the filesystem (although they > - * should not dirty new pages or inodes), writeback can run etc. After waiting > - * for all running page faults we sync the filesystem which will clean all > - * dirty pages and inodes (no new dirty pages or inodes can be created when > - * sync is running). > - * > - * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs > - * modification are blocked (e.g. XFS preallocation truncation on inode > - * reclaim). This is usually implemented by blocking new transactions for > - * filesystems that have them and need this additional guard. After all > - * internal writers are finished we call ->freeze_fs() to finish filesystem > - * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is > - * mostly auxiliary for filesystems to verify they do not modify frozen fs. > - * > - * sb->s_writers.frozen is protected by sb->s_umount. > - */ > -int freeze_super(struct super_block *sb) > +/* Caller takes lock and handles active count */ > +static int freeze_locked_super(struct super_block *sb) > { > int ret; > > - atomic_inc(&sb->s_active); > - down_write(&sb->s_umount); > - if (sb->s_writers.frozen != SB_UNFROZEN) { > - deactivate_locked_super(sb); > + if (sb->s_writers.frozen != SB_UNFROZEN) > return -EBUSY; > - } > > - if (!(sb->s_flags & SB_BORN)) { > - up_write(&sb->s_umount); > + if (!(sb->s_flags & SB_BORN)) > return 0; /* sic - it's "nothing to do" */ > - } > > if (sb_rdonly(sb)) { > /* Nothing to do really... */ > sb->s_writers.frozen = SB_FREEZE_COMPLETE; > - up_write(&sb->s_umount); > return 0; > } > > @@ -1468,7 +1429,6 @@ int freeze_super(struct super_block *sb) > sb->s_writers.frozen = SB_UNFROZEN; > sb_freeze_unlock(sb); > wake_up(&sb->s_writers.wait_unfrozen); > - deactivate_locked_super(sb); > return ret; > } > } > @@ -1478,9 +1438,59 @@ int freeze_super(struct super_block *sb) > */ > sb->s_writers.frozen = SB_FREEZE_COMPLETE; > lockdep_sb_freeze_release(sb); > - up_write(&sb->s_umount); > return 0; > } > + > +/** > + * freeze_super - lock the filesystem and force it into a consistent state > + * @sb: the super to lock > + * > + * 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 > + * -EBUSY. > + * > + * During this function, sb->s_writers.frozen goes through these values: > + * > + * SB_UNFROZEN: File system is normal, all writes progress as usual. > + * > + * SB_FREEZE_WRITE: The file system is in the process of being frozen. New > + * writes should be blocked, though page faults are still allowed. We wait for > + * all writes to complete and then proceed to the next stage. > + * > + * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked > + * but internal fs threads can still modify the filesystem (although they > + * should not dirty new pages or inodes), writeback can run etc. After waiting > + * for all running page faults we sync the filesystem which will clean all > + * dirty pages and inodes (no new dirty pages or inodes can be created when > + * sync is running). > + * > + * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs > + * modification are blocked (e.g. XFS preallocation truncation on inode > + * reclaim). This is usually implemented by blocking new transactions for > + * filesystems that have them and need this additional guard. After all > + * internal writers are finished we call ->freeze_fs() to finish filesystem > + * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is > + * mostly auxiliary for filesystems to verify they do not modify frozen fs. > + * > + * sb->s_writers.frozen is protected by sb->s_umount. > + */ > +int freeze_super(struct super_block *sb) > +{ > + int error; > + > + atomic_inc(&sb->s_active); > + > + down_write(&sb->s_umount); > + error = freeze_locked_super(sb); > + if (error) { > + deactivate_locked_super(sb); > + goto out; > + } > + up_write(&sb->s_umount); > + > +out: > + return error; > +} > EXPORT_SYMBOL(freeze_super); > > /** > -- > 2.15.0 >
diff --git a/fs/super.c b/fs/super.c index d4e33e8f1e6f..a7650ff22f0e 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1387,59 +1387,20 @@ static void sb_freeze_unlock(struct super_block *sb) percpu_up_write(sb->s_writers.rw_sem + level); } -/** - * freeze_super - lock the filesystem and force it into a consistent state - * @sb: the super to lock - * - * 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 - * -EBUSY. - * - * During this function, sb->s_writers.frozen goes through these values: - * - * SB_UNFROZEN: File system is normal, all writes progress as usual. - * - * SB_FREEZE_WRITE: The file system is in the process of being frozen. New - * writes should be blocked, though page faults are still allowed. We wait for - * all writes to complete and then proceed to the next stage. - * - * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked - * but internal fs threads can still modify the filesystem (although they - * should not dirty new pages or inodes), writeback can run etc. After waiting - * for all running page faults we sync the filesystem which will clean all - * dirty pages and inodes (no new dirty pages or inodes can be created when - * sync is running). - * - * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs - * modification are blocked (e.g. XFS preallocation truncation on inode - * reclaim). This is usually implemented by blocking new transactions for - * filesystems that have them and need this additional guard. After all - * internal writers are finished we call ->freeze_fs() to finish filesystem - * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is - * mostly auxiliary for filesystems to verify they do not modify frozen fs. - * - * sb->s_writers.frozen is protected by sb->s_umount. - */ -int freeze_super(struct super_block *sb) +/* Caller takes lock and handles active count */ +static int freeze_locked_super(struct super_block *sb) { int ret; - atomic_inc(&sb->s_active); - down_write(&sb->s_umount); - if (sb->s_writers.frozen != SB_UNFROZEN) { - deactivate_locked_super(sb); + if (sb->s_writers.frozen != SB_UNFROZEN) return -EBUSY; - } - if (!(sb->s_flags & SB_BORN)) { - up_write(&sb->s_umount); + if (!(sb->s_flags & SB_BORN)) return 0; /* sic - it's "nothing to do" */ - } if (sb_rdonly(sb)) { /* Nothing to do really... */ sb->s_writers.frozen = SB_FREEZE_COMPLETE; - up_write(&sb->s_umount); return 0; } @@ -1468,7 +1429,6 @@ int freeze_super(struct super_block *sb) sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb); wake_up(&sb->s_writers.wait_unfrozen); - deactivate_locked_super(sb); return ret; } } @@ -1478,9 +1438,59 @@ int freeze_super(struct super_block *sb) */ sb->s_writers.frozen = SB_FREEZE_COMPLETE; lockdep_sb_freeze_release(sb); - up_write(&sb->s_umount); return 0; } + +/** + * freeze_super - lock the filesystem and force it into a consistent state + * @sb: the super to lock + * + * 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 + * -EBUSY. + * + * During this function, sb->s_writers.frozen goes through these values: + * + * SB_UNFROZEN: File system is normal, all writes progress as usual. + * + * SB_FREEZE_WRITE: The file system is in the process of being frozen. New + * writes should be blocked, though page faults are still allowed. We wait for + * all writes to complete and then proceed to the next stage. + * + * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked + * but internal fs threads can still modify the filesystem (although they + * should not dirty new pages or inodes), writeback can run etc. After waiting + * for all running page faults we sync the filesystem which will clean all + * dirty pages and inodes (no new dirty pages or inodes can be created when + * sync is running). + * + * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs + * modification are blocked (e.g. XFS preallocation truncation on inode + * reclaim). This is usually implemented by blocking new transactions for + * filesystems that have them and need this additional guard. After all + * internal writers are finished we call ->freeze_fs() to finish filesystem + * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is + * mostly auxiliary for filesystems to verify they do not modify frozen fs. + * + * sb->s_writers.frozen is protected by sb->s_umount. + */ +int freeze_super(struct super_block *sb) +{ + int error; + + atomic_inc(&sb->s_active); + + down_write(&sb->s_umount); + error = freeze_locked_super(sb); + if (error) { + deactivate_locked_super(sb); + goto out; + } + up_write(&sb->s_umount); + +out: + return error; +} EXPORT_SYMBOL(freeze_super); /**
freeze_super() holds a write lock, however we wish to also enable callers which already hold the write lock. To do this provide a helper and make freeze_super() use it. This way, all that freeze_super() does now is lock handling and active count management. This change has no functional changes. Suggested-by: Dave Chinner <david@fromorbit.com> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> --- fs/super.c | 100 +++++++++++++++++++++++++++++++++---------------------------- 1 file changed, 55 insertions(+), 45 deletions(-)