| Message ID | 20201025034117.4918-3-cgxu519@mykernel.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | implement containerized syncfs for overlayfs | expand |
On Sun 25-10-20 11:41:11, Chengguang Xu wrote: > Implement overlayfs' ->writepages operation so that > we can sync dirty data/metadata to upper filesystem. > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> > --- > fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > index b584dca845ba..f27fc5be34df 100644 > --- a/fs/overlayfs/inode.c > +++ b/fs/overlayfs/inode.c > @@ -11,6 +11,7 @@ > #include <linux/posix_acl.h> > #include <linux/ratelimit.h> > #include <linux/fiemap.h> > +#include <linux/writeback.h> > #include "overlayfs.h" > > > @@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = { > .update_time = ovl_update_time, > }; > > +static int ovl_writepages(struct address_space *mapping, > + struct writeback_control *wbc) > +{ > + struct inode *upper_inode = ovl_inode_upper(mapping->host); > + struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info; > + struct writeback_control tmp_wbc = *wbc; > + > + if (!ovl_should_sync(ofs)) > + return 0; > + > + /* > + * for sync(2) writeback, it has a separate external IO > + * completion path by checking PAGECACHE_TAG_WRITEBACK > + * in pagecache, we have to set for_sync to 0 in thie case, > + * let writeback waits completion after syncing individual > + * dirty inode, because we haven't implemented overlayfs' > + * own pagecache yet. > + */ > + if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL)) > + tmp_wbc.for_sync = 0; This looks really hacky as it closely depends on the internal details of writeback implementation. I'd be more open to say export wait_sb_inodes() for overlayfs use... Because that's what I gather you need in your overlayfs ->syncfs() implementation. Honza > + > + return sync_inode(upper_inode, &tmp_wbc); > +} > + > static const struct address_space_operations ovl_aops = { > + .writepages = ovl_writepages, > /* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */ > .direct_IO = noop_direct_IO, > }; > -- > 2.26.2 > >
---- 在 星期二, 2020-11-03 01:17:41 Jan Kara <jack@suse.cz> 撰写 ---- > On Sun 25-10-20 11:41:11, Chengguang Xu wrote: > > Implement overlayfs' ->writepages operation so that > > we can sync dirty data/metadata to upper filesystem. > > > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> > > --- > > fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++ > > 1 file changed, 26 insertions(+) > > > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > > index b584dca845ba..f27fc5be34df 100644 > > --- a/fs/overlayfs/inode.c > > +++ b/fs/overlayfs/inode.c > > @@ -11,6 +11,7 @@ > > #include <linux/posix_acl.h> > > #include <linux/ratelimit.h> > > #include <linux/fiemap.h> > > +#include <linux/writeback.h> > > #include "overlayfs.h" > > > > > > @@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = { > > .update_time = ovl_update_time, > > }; > > > > +static int ovl_writepages(struct address_space *mapping, > > + struct writeback_control *wbc) > > +{ > > + struct inode *upper_inode = ovl_inode_upper(mapping->host); > > + struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info; > > + struct writeback_control tmp_wbc = *wbc; > > + > > + if (!ovl_should_sync(ofs)) > > + return 0; > > + > > + /* > > + * for sync(2) writeback, it has a separate external IO > > + * completion path by checking PAGECACHE_TAG_WRITEBACK > > + * in pagecache, we have to set for_sync to 0 in thie case, > > + * let writeback waits completion after syncing individual > > + * dirty inode, because we haven't implemented overlayfs' > > + * own pagecache yet. > > + */ > > + if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL)) > > + tmp_wbc.for_sync = 0; > > This looks really hacky as it closely depends on the internal details of > writeback implementation. I'd be more open to say export wait_sb_inodes() > for overlayfs use... Because that's what I gather you need in your > overlayfs ->syncfs() implementation. > Does that mean we gather synced overlay's inode into a new waiting list(overlay's) and do the waiting behavior in overlay's ->syncfs() ? Thanks, Chengguang
On Wed 04-11-20 20:18:16, Chengguang Xu wrote: > ---- 在 星期二, 2020-11-03 01:17:41 Jan Kara <jack@suse.cz> 撰写 ---- > > On Sun 25-10-20 11:41:11, Chengguang Xu wrote: > > > Implement overlayfs' ->writepages operation so that > > > we can sync dirty data/metadata to upper filesystem. > > > > > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> > > > --- > > > fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++ > > > 1 file changed, 26 insertions(+) > > > > > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > > > index b584dca845ba..f27fc5be34df 100644 > > > --- a/fs/overlayfs/inode.c > > > +++ b/fs/overlayfs/inode.c > > > @@ -11,6 +11,7 @@ > > > #include <linux/posix_acl.h> > > > #include <linux/ratelimit.h> > > > #include <linux/fiemap.h> > > > +#include <linux/writeback.h> > > > #include "overlayfs.h" > > > > > > > > > @@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = { > > > .update_time = ovl_update_time, > > > }; > > > > > > +static int ovl_writepages(struct address_space *mapping, > > > + struct writeback_control *wbc) > > > +{ > > > + struct inode *upper_inode = ovl_inode_upper(mapping->host); > > > + struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info; > > > + struct writeback_control tmp_wbc = *wbc; > > > + > > > + if (!ovl_should_sync(ofs)) > > > + return 0; > > > + > > > + /* > > > + * for sync(2) writeback, it has a separate external IO > > > + * completion path by checking PAGECACHE_TAG_WRITEBACK > > > + * in pagecache, we have to set for_sync to 0 in thie case, > > > + * let writeback waits completion after syncing individual > > > + * dirty inode, because we haven't implemented overlayfs' > > > + * own pagecache yet. > > > + */ > > > + if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL)) > > > + tmp_wbc.for_sync = 0; > > > > This looks really hacky as it closely depends on the internal details of > > writeback implementation. I'd be more open to say export wait_sb_inodes() > > for overlayfs use... Because that's what I gather you need in your > > overlayfs ->syncfs() implementation. > > > > Does that mean we gather synced overlay's inode into a new waiting list(overlay's) and > do the waiting behavior in overlay's ->syncfs() ? My idea was that you'd just use the standard writeback logic which ends up gathering upper_sb inodes in the upper_sb->s_inodes_wb and then wait for them in overlay's ->syncfs(). Maybe we'll end up waiting for more inodes than strictly necessary but it shouldn't be too bad I'd say... Honza
---- 在 星期四, 2020-11-05 21:55:06 Jan Kara <jack@suse.cz> 撰写 ---- > On Wed 04-11-20 20:18:16, Chengguang Xu wrote: > > ---- 在 星期二, 2020-11-03 01:17:41 Jan Kara <jack@suse.cz> 撰写 ---- > > > On Sun 25-10-20 11:41:11, Chengguang Xu wrote: > > > > Implement overlayfs' ->writepages operation so that > > > > we can sync dirty data/metadata to upper filesystem. > > > > > > > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> > > > > --- > > > > fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++ > > > > 1 file changed, 26 insertions(+) > > > > > > > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > > > > index b584dca845ba..f27fc5be34df 100644 > > > > --- a/fs/overlayfs/inode.c > > > > +++ b/fs/overlayfs/inode.c > > > > @@ -11,6 +11,7 @@ > > > > #include <linux/posix_acl.h> > > > > #include <linux/ratelimit.h> > > > > #include <linux/fiemap.h> > > > > +#include <linux/writeback.h> > > > > #include "overlayfs.h" > > > > > > > > > > > > @@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = { > > > > .update_time = ovl_update_time, > > > > }; > > > > > > > > +static int ovl_writepages(struct address_space *mapping, > > > > + struct writeback_control *wbc) > > > > +{ > > > > + struct inode *upper_inode = ovl_inode_upper(mapping->host); > > > > + struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info; > > > > + struct writeback_control tmp_wbc = *wbc; > > > > + > > > > + if (!ovl_should_sync(ofs)) > > > > + return 0; > > > > + > > > > + /* > > > > + * for sync(2) writeback, it has a separate external IO > > > > + * completion path by checking PAGECACHE_TAG_WRITEBACK > > > > + * in pagecache, we have to set for_sync to 0 in thie case, > > > > + * let writeback waits completion after syncing individual > > > > + * dirty inode, because we haven't implemented overlayfs' > > > > + * own pagecache yet. > > > > + */ > > > > + if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL)) > > > > + tmp_wbc.for_sync = 0; > > > > > > This looks really hacky as it closely depends on the internal details of > > > writeback implementation. I'd be more open to say export wait_sb_inodes() > > > for overlayfs use... Because that's what I gather you need in your > > > overlayfs ->syncfs() implementation. > > > > > > > Does that mean we gather synced overlay's inode into a new waiting list(overlay's) and > > do the waiting behavior in overlay's ->syncfs() ? > > My idea was that you'd just use the standard writeback logic which ends up > gathering upper_sb inodes in the upper_sb->s_inodes_wb and then wait for > them in overlay's ->syncfs(). Maybe we'll end up waiting for more inodes > than strictly necessary but it shouldn't be too bad I'd say... > Yeah, I agree with you, I'll modify in next version. Thanks, Chengguang
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index b584dca845ba..f27fc5be34df 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -11,6 +11,7 @@ #include <linux/posix_acl.h> #include <linux/ratelimit.h> #include <linux/fiemap.h> +#include <linux/writeback.h> #include "overlayfs.h" @@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = { .update_time = ovl_update_time, }; +static int ovl_writepages(struct address_space *mapping, + struct writeback_control *wbc) +{ + struct inode *upper_inode = ovl_inode_upper(mapping->host); + struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info; + struct writeback_control tmp_wbc = *wbc; + + if (!ovl_should_sync(ofs)) + return 0; + + /* + * for sync(2) writeback, it has a separate external IO + * completion path by checking PAGECACHE_TAG_WRITEBACK + * in pagecache, we have to set for_sync to 0 in thie case, + * let writeback waits completion after syncing individual + * dirty inode, because we haven't implemented overlayfs' + * own pagecache yet. + */ + if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL)) + tmp_wbc.for_sync = 0; + + return sync_inode(upper_inode, &tmp_wbc); +} + static const struct address_space_operations ovl_aops = { + .writepages = ovl_writepages, /* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */ .direct_IO = noop_direct_IO, };
Implement overlayfs' ->writepages operation so that we can sync dirty data/metadata to upper filesystem. Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> --- fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+)