| Message ID | 20201216143802.GA10550@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vfs, syncfs: Do not ignore return code from ->sync_fs() | expand |
On Wed, 2020-12-16 at 09:38 -0500, Vivek Goyal wrote: > I see that current implementation of __sync_filesystem() ignores the > return code from ->sync_fs(). I am not sure why that's the case. > > Ignoring ->sync_fs() return code is problematic for overlayfs where > it can return error if sync_filesystem() on upper super block failed. > That error will simply be lost and sycnfs(overlay_fd), will get > success (despite the fact it failed). > > I am assuming that we want to continue to call __sync_blockdev() > despite the fact that there have been errors reported from > ->sync_fs(). So I wrote this simple patch which captures the > error from ->sync_fs() but continues to call __sync_blockdev() > and returns error from sync_fs() if there is one. > > There might be some very good reasons to not capture ->sync_fs() > return code, I don't know. Hence thought of proposing this patch. > Atleast I will get to know the reason. I still need to figure > a way out how to propagate overlay sync_fs() errors to user > space. > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > --- > fs/sync.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > Index: redhat-linux/fs/sync.c > =================================================================== > --- redhat-linux.orig/fs/sync.c 2020-12-16 09:15:49.831565653 -0500 > +++ redhat-linux/fs/sync.c 2020-12-16 09:23:42.499853207 -0500 > @@ -30,14 +30,18 @@ > */ > static int __sync_filesystem(struct super_block *sb, int wait) > { > + int ret, ret2; > + > if (wait) > sync_inodes_sb(sb); > else > writeback_inodes_sb(sb, WB_REASON_SYNC); > > > if (sb->s_op->sync_fs) > - sb->s_op->sync_fs(sb, wait); > - return __sync_blockdev(sb->s_bdev, wait); > + ret = sb->s_op->sync_fs(sb, wait); > + ret2 = __sync_blockdev(sb->s_bdev, wait); > + > + return ret ? ret : ret2; > } > > > /* > I posted a patchset that took a similar approach a couple of years ago, and we decided not to go with it [1]. While it's not ideal to ignore the error here, I think this is likely to break stuff. What may be better is to just make sync_fs void return, so people don't think that returned errors there mean anything. [1]: https://lore.kernel.org/linux-fsdevel/20180518123415.28181-1-jlayton@kernel.org/
On Wed, Dec 16, 2020 at 09:57:49AM -0500, Jeff Layton wrote: > On Wed, 2020-12-16 at 09:38 -0500, Vivek Goyal wrote: > > I see that current implementation of __sync_filesystem() ignores the > > return code from ->sync_fs(). I am not sure why that's the case. > > > > Ignoring ->sync_fs() return code is problematic for overlayfs where > > it can return error if sync_filesystem() on upper super block failed. > > That error will simply be lost and sycnfs(overlay_fd), will get > > success (despite the fact it failed). > > > > I am assuming that we want to continue to call __sync_blockdev() > > despite the fact that there have been errors reported from > > ->sync_fs(). So I wrote this simple patch which captures the > > error from ->sync_fs() but continues to call __sync_blockdev() > > and returns error from sync_fs() if there is one. > > > > There might be some very good reasons to not capture ->sync_fs() > > return code, I don't know. Hence thought of proposing this patch. > > Atleast I will get to know the reason. I still need to figure > > a way out how to propagate overlay sync_fs() errors to user > > space. > > > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > > --- > > fs/sync.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > Index: redhat-linux/fs/sync.c > > =================================================================== > > --- redhat-linux.orig/fs/sync.c 2020-12-16 09:15:49.831565653 -0500 > > +++ redhat-linux/fs/sync.c 2020-12-16 09:23:42.499853207 -0500 > > @@ -30,14 +30,18 @@ > > */ > > static int __sync_filesystem(struct super_block *sb, int wait) > > { > > + int ret, ret2; > > + > > if (wait) > > sync_inodes_sb(sb); > > else > > writeback_inodes_sb(sb, WB_REASON_SYNC); > > > > > > if (sb->s_op->sync_fs) > > - sb->s_op->sync_fs(sb, wait); > > - return __sync_blockdev(sb->s_bdev, wait); > > + ret = sb->s_op->sync_fs(sb, wait); > > + ret2 = __sync_blockdev(sb->s_bdev, wait); > > + > > + return ret ? ret : ret2; > > } > > > > > > /* > > > > I posted a patchset that took a similar approach a couple of years ago, > and we decided not to go with it [1]. > > While it's not ideal to ignore the error here, I think this is likely to > break stuff. So one side affect I see is that syncfs() might start returning errors in some cases which were not reported at all. I am wondering will that count as breakage. > What may be better is to just make sync_fs void return, so > people don't think that returned errors there mean anything. May be. But then question remains that how do we return error to user space in syncfs(fd) for overlayfs. I will not be surprised if other filesystems want to return errors as well. Shall I create new helpers and call these in case of syncfs(). But that too will start returning new errors on syncfs(). So it does not solve that problem (if it is a problem). Or we can define a new super block op say ->sync_fs2() and call that first and in that case capture return code. That way it will not impact existing cases and overlayfs can possibly make use of ->sync_fs2() and return error. IOW, impact will be limited to only file systems which chose to implement ->sync_fs2(). Thanks Vivek > > [1]: https://lore.kernel.org/linux-fsdevel/20180518123415.28181-1-jlayton@kernel.org/ > -- > Jeff Layton <jlayton@kernel.org> >
On Wed, 2020-12-16 at 10:14 -0500, Vivek Goyal wrote: > On Wed, Dec 16, 2020 at 09:57:49AM -0500, Jeff Layton wrote: > > On Wed, 2020-12-16 at 09:38 -0500, Vivek Goyal wrote: > > > I see that current implementation of __sync_filesystem() ignores the > > > return code from ->sync_fs(). I am not sure why that's the case. > > > > > > Ignoring ->sync_fs() return code is problematic for overlayfs where > > > it can return error if sync_filesystem() on upper super block failed. > > > That error will simply be lost and sycnfs(overlay_fd), will get > > > success (despite the fact it failed). > > > > > > I am assuming that we want to continue to call __sync_blockdev() > > > despite the fact that there have been errors reported from > > > ->sync_fs(). So I wrote this simple patch which captures the > > > error from ->sync_fs() but continues to call __sync_blockdev() > > > and returns error from sync_fs() if there is one. > > > > > > There might be some very good reasons to not capture ->sync_fs() > > > return code, I don't know. Hence thought of proposing this patch. > > > Atleast I will get to know the reason. I still need to figure > > > a way out how to propagate overlay sync_fs() errors to user > > > space. > > > > > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > > > --- > > > fs/sync.c | 8 ++++++-- > > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > > > Index: redhat-linux/fs/sync.c > > > =================================================================== > > > --- redhat-linux.orig/fs/sync.c 2020-12-16 09:15:49.831565653 -0500 > > > +++ redhat-linux/fs/sync.c 2020-12-16 09:23:42.499853207 -0500 > > > @@ -30,14 +30,18 @@ > > > */ > > > static int __sync_filesystem(struct super_block *sb, int wait) > > > { > > > + int ret, ret2; > > > + > > > if (wait) > > > sync_inodes_sb(sb); > > > else > > > writeback_inodes_sb(sb, WB_REASON_SYNC); > > > > > > > > > if (sb->s_op->sync_fs) > > > - sb->s_op->sync_fs(sb, wait); > > > - return __sync_blockdev(sb->s_bdev, wait); > > > + ret = sb->s_op->sync_fs(sb, wait); > > > + ret2 = __sync_blockdev(sb->s_bdev, wait); > > > + > > > + return ret ? ret : ret2; > > > } > > > > > > > > > /* > > > > > > > I posted a patchset that took a similar approach a couple of years ago, > > and we decided not to go with it [1]. > > > > While it's not ideal to ignore the error here, I think this is likely to > > break stuff. > > So one side affect I see is that syncfs() might start returning errors > in some cases which were not reported at all. I am wondering will that > count as breakage. > > > What may be better is to just make sync_fs void return, so > > people don't think that returned errors there mean anything. > > May be. > > But then question remains that how do we return error to user space > in syncfs(fd) for overlayfs. I will not be surprised if other > filesystems want to return errors as well. > > Shall I create new helpers and call these in case of syncfs(). But > that too will start returning new errors on syncfs(). So it does > not solve that problem (if it is a problem). > > Or we can define a new super block op say ->sync_fs2() and call that > first and in that case capture return code. That way it will not > impact existing cases and overlayfs can possibly make use of > ->sync_fs2() and return error. IOW, impact will be limited to > only file systems which chose to implement ->sync_fs2(). > > Thanks > Vivek > Sure, it's possible to add a sb->sync_fs2, but the problem is that sync_fs is a superblock op, and is missing a lot of important context about how it got called. syncfs(2) syscall takes a file descriptor argument. I'd add a new f_op- >syncfs vector and turn most of the current guts of the syncfs syscall into a generic_syncfs() that gets called when f_op->syncfs isn't defined. Overlayfs could then add a ->syncfs op that would give it control over what error gets returned. With that, you could basically leave the old sb->sync_fs routine alone. I think that's probably the safest approach for allowing overlayfs to propagate syncfs errors from the upper layer to the overlay.
On Wed, 2020-12-16 at 10:44 -0500, Jeff Layton wrote: > On Wed, 2020-12-16 at 10:14 -0500, Vivek Goyal wrote: > > On Wed, Dec 16, 2020 at 09:57:49AM -0500, Jeff Layton wrote: > > > On Wed, 2020-12-16 at 09:38 -0500, Vivek Goyal wrote: > > > > I see that current implementation of __sync_filesystem() ignores the > > > > return code from ->sync_fs(). I am not sure why that's the case. > > > > > > > > Ignoring ->sync_fs() return code is problematic for overlayfs where > > > > it can return error if sync_filesystem() on upper super block failed. > > > > That error will simply be lost and sycnfs(overlay_fd), will get > > > > success (despite the fact it failed). > > > > > > > > I am assuming that we want to continue to call __sync_blockdev() > > > > despite the fact that there have been errors reported from > > > > ->sync_fs(). So I wrote this simple patch which captures the > > > > error from ->sync_fs() but continues to call __sync_blockdev() > > > > and returns error from sync_fs() if there is one. > > > > > > > > There might be some very good reasons to not capture ->sync_fs() > > > > return code, I don't know. Hence thought of proposing this patch. > > > > Atleast I will get to know the reason. I still need to figure > > > > a way out how to propagate overlay sync_fs() errors to user > > > > space. > > > > > > > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > > > > --- > > > > fs/sync.c | 8 ++++++-- > > > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > > > > > Index: redhat-linux/fs/sync.c > > > > =================================================================== > > > > --- redhat-linux.orig/fs/sync.c 2020-12-16 09:15:49.831565653 -0500 > > > > +++ redhat-linux/fs/sync.c 2020-12-16 09:23:42.499853207 -0500 > > > > @@ -30,14 +30,18 @@ > > > > */ > > > > static int __sync_filesystem(struct super_block *sb, int wait) > > > > { > > > > + int ret, ret2; > > > > + > > > > if (wait) > > > > sync_inodes_sb(sb); > > > > else > > > > writeback_inodes_sb(sb, WB_REASON_SYNC); > > > > > > > > > > > > if (sb->s_op->sync_fs) > > > > - sb->s_op->sync_fs(sb, wait); > > > > - return __sync_blockdev(sb->s_bdev, wait); > > > > + ret = sb->s_op->sync_fs(sb, wait); > > > > + ret2 = __sync_blockdev(sb->s_bdev, wait); > > > > + > > > > + return ret ? ret : ret2; > > > > } > > > > > > > > > > > > /* > > > > > > > > > > I posted a patchset that took a similar approach a couple of years ago, > > > and we decided not to go with it [1]. > > > > > > While it's not ideal to ignore the error here, I think this is likely to > > > break stuff. > > > > So one side affect I see is that syncfs() might start returning errors > > in some cases which were not reported at all. I am wondering will that > > count as breakage. > > > > > What may be better is to just make sync_fs void return, so > > > people don't think that returned errors there mean anything. > > > > May be. > > > > But then question remains that how do we return error to user space > > in syncfs(fd) for overlayfs. I will not be surprised if other > > filesystems want to return errors as well. > > > > Shall I create new helpers and call these in case of syncfs(). But > > that too will start returning new errors on syncfs(). So it does > > not solve that problem (if it is a problem). > > > > Or we can define a new super block op say ->sync_fs2() and call that > > first and in that case capture return code. That way it will not > > impact existing cases and overlayfs can possibly make use of > > ->sync_fs2() and return error. IOW, impact will be limited to > > only file systems which chose to implement ->sync_fs2(). > > > > Thanks > > Vivek > > > > Sure, it's possible to add a sb->sync_fs2, but the problem is that > sync_fs is a superblock op, and is missing a lot of important context > about how it got called. > > syncfs(2) syscall takes a file descriptor argument. I'd add a new f_op- > > syncfs vector and turn most of the current guts of the syncfs syscall > into a generic_syncfs() that gets called when f_op->syncfs isn't > defined. > > Overlayfs could then add a ->syncfs op that would give it control over > what error gets returned. With that, you could basically leave the old > sb->sync_fs routine alone. > > I think that's probably the safest approach for allowing overlayfs to > propagate syncfs errors from the upper layer to the overlay. > To be clear, I mean something like this (draft, untested) patch. You'd also need to add a new ->syncfs op for overlayfs, and that could just do a check_and_advance against the upper layer sb's errseq_t after calling sync_filesystem. -----------------------8<------------------------- [PATCH] vfs: add new f_op->syncfs vector Signed-off-by: Jeff Layton <jlayton@kernel.org> --- fs/sync.c | 30 +++++++++++++++++++++--------- include/linux/fs.h | 1 + 2 files changed, 22 insertions(+), 9 deletions(-) diff --git a/fs/sync.c b/fs/sync.c index 1373a610dc78..fc7f73762b9e 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -155,27 +155,39 @@ void emergency_sync(void) } } +static int generic_syncfs(struct file *file) +{ + int ret, ret2; + struct super_block *sb = file->f_path.dentry->d_sb; + + down_read(&sb->s_umount); + ret = sync_filesystem(sb); + up_read(&sb->s_umount); + + ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err); + + fdput(f); + return ret ? ret : ret2; +} + /* * sync a single super */ SYSCALL_DEFINE1(syncfs, int, fd) { struct fd f = fdget(fd); - struct super_block *sb; - int ret, ret2; + int ret; if (!f.file) return -EBADF; - sb = f.file->f_path.dentry->d_sb; - down_read(&sb->s_umount); - ret = sync_filesystem(sb); - up_read(&sb->s_umount); - - ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err); + if (f.file->f_op->syncfs) + ret = f.file->f_op->syncfs(f.file); + else + ret = generic_syncfs(f.file); fdput(f); - return ret ? ret : ret2; + return ret; } /** diff --git a/include/linux/fs.h b/include/linux/fs.h index 8667d0cdc71e..6710469b7e33 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1859,6 +1859,7 @@ struct file_operations { struct file *file_out, loff_t pos_out, loff_t len, unsigned int remap_flags); int (*fadvise)(struct file *, loff_t, loff_t, int); + int (*syncfs)(struct file *); } __randomize_layout; struct inode_operations {
On Wed, Dec 16, 2020 at 10:53:16AM -0500, Jeff Layton wrote: > On Wed, 2020-12-16 at 10:44 -0500, Jeff Layton wrote: > > On Wed, 2020-12-16 at 10:14 -0500, Vivek Goyal wrote: > > > On Wed, Dec 16, 2020 at 09:57:49AM -0500, Jeff Layton wrote: > > > > On Wed, 2020-12-16 at 09:38 -0500, Vivek Goyal wrote: > > > > > I see that current implementation of __sync_filesystem() ignores the > > > > > return code from ->sync_fs(). I am not sure why that's the case. > > > > > > > > > > Ignoring ->sync_fs() return code is problematic for overlayfs where > > > > > it can return error if sync_filesystem() on upper super block failed. > > > > > That error will simply be lost and sycnfs(overlay_fd), will get > > > > > success (despite the fact it failed). > > > > > > > > > > I am assuming that we want to continue to call __sync_blockdev() > > > > > despite the fact that there have been errors reported from > > > > > ->sync_fs(). So I wrote this simple patch which captures the > > > > > error from ->sync_fs() but continues to call __sync_blockdev() > > > > > and returns error from sync_fs() if there is one. > > > > > > > > > > There might be some very good reasons to not capture ->sync_fs() > > > > > return code, I don't know. Hence thought of proposing this patch. > > > > > Atleast I will get to know the reason. I still need to figure > > > > > a way out how to propagate overlay sync_fs() errors to user > > > > > space. > > > > > > > > > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > > > > > --- > > > > > fs/sync.c | 8 ++++++-- > > > > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > > > > > > > Index: redhat-linux/fs/sync.c > > > > > =================================================================== > > > > > --- redhat-linux.orig/fs/sync.c 2020-12-16 09:15:49.831565653 -0500 > > > > > +++ redhat-linux/fs/sync.c 2020-12-16 09:23:42.499853207 -0500 > > > > > @@ -30,14 +30,18 @@ > > > > > */ > > > > > static int __sync_filesystem(struct super_block *sb, int wait) > > > > > { > > > > > + int ret, ret2; > > > > > + > > > > > if (wait) > > > > > sync_inodes_sb(sb); > > > > > else > > > > > writeback_inodes_sb(sb, WB_REASON_SYNC); > > > > > > > > > > > > > > > if (sb->s_op->sync_fs) > > > > > - sb->s_op->sync_fs(sb, wait); > > > > > - return __sync_blockdev(sb->s_bdev, wait); > > > > > + ret = sb->s_op->sync_fs(sb, wait); > > > > > + ret2 = __sync_blockdev(sb->s_bdev, wait); > > > > > + > > > > > + return ret ? ret : ret2; > > > > > } > > > > > > > > > > > > > > > /* > > > > > > > > > > > > > I posted a patchset that took a similar approach a couple of years ago, > > > > and we decided not to go with it [1]. > > > > > > > > While it's not ideal to ignore the error here, I think this is likely to > > > > break stuff. > > > > > > So one side affect I see is that syncfs() might start returning errors > > > in some cases which were not reported at all. I am wondering will that > > > count as breakage. > > > > > > > What may be better is to just make sync_fs void return, so > > > > people don't think that returned errors there mean anything. > > > > > > May be. > > > > > > But then question remains that how do we return error to user space > > > in syncfs(fd) for overlayfs. I will not be surprised if other > > > filesystems want to return errors as well. > > > > > > Shall I create new helpers and call these in case of syncfs(). But > > > that too will start returning new errors on syncfs(). So it does > > > not solve that problem (if it is a problem). > > > > > > Or we can define a new super block op say ->sync_fs2() and call that > > > first and in that case capture return code. That way it will not > > > impact existing cases and overlayfs can possibly make use of > > > ->sync_fs2() and return error. IOW, impact will be limited to > > > only file systems which chose to implement ->sync_fs2(). > > > > > > Thanks > > > Vivek > > > > > > > Sure, it's possible to add a sb->sync_fs2, but the problem is that > > sync_fs is a superblock op, and is missing a lot of important context > > about how it got called. > > > > syncfs(2) syscall takes a file descriptor argument. I'd add a new f_op- > > > syncfs vector and turn most of the current guts of the syncfs syscall > > into a generic_syncfs() that gets called when f_op->syncfs isn't > > defined. > > > > Overlayfs could then add a ->syncfs op that would give it control over > > what error gets returned. With that, you could basically leave the old > > sb->sync_fs routine alone. > > > > I think that's probably the safest approach for allowing overlayfs to > > propagate syncfs errors from the upper layer to the overlay. > > > > To be clear, I mean something like this (draft, untested) patch. You'd > also need to add a new ->syncfs op for overlayfs, and that could just do > a check_and_advance against the upper layer sb's errseq_t after calling > sync_filesystem. Hi Jeff, This sounds interesting. Should work for overlayfs. Will make overlayfs changes. So basically a new file operations ->syncfs() which says sync filesystem containing this file. Error code will be captured and returned to user space. Also filesystem is responsible to check for writeback errors. Thanks Vivek > > -----------------------8<------------------------- > > [PATCH] vfs: add new f_op->syncfs vector > > Signed-off-by: Jeff Layton <jlayton@kernel.org> > --- > fs/sync.c | 30 +++++++++++++++++++++--------- > include/linux/fs.h | 1 + > 2 files changed, 22 insertions(+), 9 deletions(-) > > diff --git a/fs/sync.c b/fs/sync.c > index 1373a610dc78..fc7f73762b9e 100644 > --- a/fs/sync.c > +++ b/fs/sync.c > @@ -155,27 +155,39 @@ void emergency_sync(void) > } > } > > +static int generic_syncfs(struct file *file) > +{ > + int ret, ret2; > + struct super_block *sb = file->f_path.dentry->d_sb; > + > + down_read(&sb->s_umount); > + ret = sync_filesystem(sb); > + up_read(&sb->s_umount); > + > + ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err); > + > + fdput(f); > + return ret ? ret : ret2; > +} > + > /* > * sync a single super > */ > SYSCALL_DEFINE1(syncfs, int, fd) > { > struct fd f = fdget(fd); > - struct super_block *sb; > - int ret, ret2; > + int ret; > > if (!f.file) > return -EBADF; > - sb = f.file->f_path.dentry->d_sb; > > - down_read(&sb->s_umount); > - ret = sync_filesystem(sb); > - up_read(&sb->s_umount); > - > - ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err); > + if (f.file->f_op->syncfs) > + ret = f.file->f_op->syncfs(f.file); > + else > + ret = generic_syncfs(f.file); > > fdput(f); > - return ret ? ret : ret2; > + return ret; > } > > /** > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 8667d0cdc71e..6710469b7e33 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1859,6 +1859,7 @@ struct file_operations { > struct file *file_out, loff_t pos_out, > loff_t len, unsigned int remap_flags); > int (*fadvise)(struct file *, loff_t, loff_t, int); > + int (*syncfs)(struct file *); > } __randomize_layout; > > struct inode_operations { > -- > 2.29.2 > > >
Index: redhat-linux/fs/sync.c =================================================================== --- redhat-linux.orig/fs/sync.c 2020-12-16 09:15:49.831565653 -0500 +++ redhat-linux/fs/sync.c 2020-12-16 09:23:42.499853207 -0500 @@ -30,14 +30,18 @@ */ static int __sync_filesystem(struct super_block *sb, int wait) { + int ret, ret2; + if (wait) sync_inodes_sb(sb); else writeback_inodes_sb(sb, WB_REASON_SYNC); if (sb->s_op->sync_fs) - sb->s_op->sync_fs(sb, wait); - return __sync_blockdev(sb->s_bdev, wait); + ret = sb->s_op->sync_fs(sb, wait); + ret2 = __sync_blockdev(sb->s_bdev, wait); + + return ret ? ret : ret2; } /*
I see that current implementation of __sync_filesystem() ignores the return code from ->sync_fs(). I am not sure why that's the case. Ignoring ->sync_fs() return code is problematic for overlayfs where it can return error if sync_filesystem() on upper super block failed. That error will simply be lost and sycnfs(overlay_fd), will get success (despite the fact it failed). I am assuming that we want to continue to call __sync_blockdev() despite the fact that there have been errors reported from ->sync_fs(). So I wrote this simple patch which captures the error from ->sync_fs() but continues to call __sync_blockdev() and returns error from sync_fs() if there is one. There might be some very good reasons to not capture ->sync_fs() return code, I don't know. Hence thought of proposing this patch. Atleast I will get to know the reason. I still need to figure a way out how to propagate overlay sync_fs() errors to user space. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> --- fs/sync.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)