| Message ID | 20250312161941.1261615-1-mjguzik@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fs: use debug-only asserts around fd allocation and install | expand |
On Wed 12-03-25 17:19:41, Mateusz Guzik wrote: > This also restores the check which got removed in 52732bb9abc9ee5b > ("fs/file.c: remove sanity_check and add likely/unlikely in alloc_fd()") > for performance reasons -- they no longer apply with a debug-only > variant. > > Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Looks good. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > > I have about 0 opinion whether this should be BUG or WARN, the code was > already inconsistent on this front. If you want the latter, I'll have 0 > complaints if you just sed it and commit as yours. > > This reminded me to sort out that litmus test for smp_rmb, hopefully > soon(tm) as it is now nagging me. > > fs/file.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/file.c b/fs/file.c > index 6c159ede55f1..09460ec74ef8 100644 > --- a/fs/file.c > +++ b/fs/file.c > @@ -582,6 +582,7 @@ static int alloc_fd(unsigned start, unsigned end, unsigned flags) > > __set_open_fd(fd, fdt, flags & O_CLOEXEC); > error = fd; > + VFS_BUG_ON(rcu_access_pointer(fdt->fd[fd]) != NULL); > > out: > spin_unlock(&files->file_lock); > @@ -647,7 +648,7 @@ void fd_install(unsigned int fd, struct file *file) > rcu_read_unlock_sched(); > spin_lock(&files->file_lock); > fdt = files_fdtable(files); > - WARN_ON(fdt->fd[fd] != NULL); > + VFS_BUG_ON(fdt->fd[fd] != NULL); > rcu_assign_pointer(fdt->fd[fd], file); > spin_unlock(&files->file_lock); > return; > @@ -655,7 +656,7 @@ void fd_install(unsigned int fd, struct file *file) > /* coupled with smp_wmb() in expand_fdtable() */ > smp_rmb(); > fdt = rcu_dereference_sched(files->fdt); > - BUG_ON(fdt->fd[fd] != NULL); > + VFS_BUG_ON(fdt->fd[fd] != NULL); > rcu_assign_pointer(fdt->fd[fd], file); > rcu_read_unlock_sched(); > } > -- > 2.43.0 >
On Wed, Mar 12, 2025 at 5:19 PM Mateusz Guzik <mjguzik@gmail.com> wrote: > > This also restores the check which got removed in 52732bb9abc9ee5b > ("fs/file.c: remove sanity_check and add likely/unlikely in alloc_fd()") > for performance reasons -- they no longer apply with a debug-only > variant. > > Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> > --- > > I have about 0 opinion whether this should be BUG or WARN, the code was > already inconsistent on this front. If you want the latter, I'll have 0 > complaints if you just sed it and commit as yours. > > This reminded me to sort out that litmus test for smp_rmb, hopefully > soon(tm) as it is now nagging me. > > fs/file.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/file.c b/fs/file.c > index 6c159ede55f1..09460ec74ef8 100644 > --- a/fs/file.c > +++ b/fs/file.c > @@ -582,6 +582,7 @@ static int alloc_fd(unsigned start, unsigned end, unsigned flags) > > __set_open_fd(fd, fdt, flags & O_CLOEXEC); > error = fd; > + VFS_BUG_ON(rcu_access_pointer(fdt->fd[fd]) != NULL); > when restoring this check i dutifully copy-pasted the original. I only now mentally registered it uses a rcu primitive to do the load, while the others do a plain load. arguably the former is closer to being correct and it definitely does not hurt so this line should replace the other 2 lines below. i can send a v2 to that effect, but given the triviality of the edit, perhaps you will be happy to sort it out > out: > spin_unlock(&files->file_lock); > @@ -647,7 +648,7 @@ void fd_install(unsigned int fd, struct file *file) > rcu_read_unlock_sched(); > spin_lock(&files->file_lock); > fdt = files_fdtable(files); > - WARN_ON(fdt->fd[fd] != NULL); > + VFS_BUG_ON(fdt->fd[fd] != NULL); > rcu_assign_pointer(fdt->fd[fd], file); > spin_unlock(&files->file_lock); > return; > @@ -655,7 +656,7 @@ void fd_install(unsigned int fd, struct file *file) > /* coupled with smp_wmb() in expand_fdtable() */ > smp_rmb(); > fdt = rcu_dereference_sched(files->fdt); > - BUG_ON(fdt->fd[fd] != NULL); > + VFS_BUG_ON(fdt->fd[fd] != NULL); > rcu_assign_pointer(fdt->fd[fd], file); > rcu_read_unlock_sched(); > } > -- > 2.43.0 >
diff --git a/fs/file.c b/fs/file.c index 6c159ede55f1..09460ec74ef8 100644 --- a/fs/file.c +++ b/fs/file.c @@ -582,6 +582,7 @@ static int alloc_fd(unsigned start, unsigned end, unsigned flags) __set_open_fd(fd, fdt, flags & O_CLOEXEC); error = fd; + VFS_BUG_ON(rcu_access_pointer(fdt->fd[fd]) != NULL); out: spin_unlock(&files->file_lock); @@ -647,7 +648,7 @@ void fd_install(unsigned int fd, struct file *file) rcu_read_unlock_sched(); spin_lock(&files->file_lock); fdt = files_fdtable(files); - WARN_ON(fdt->fd[fd] != NULL); + VFS_BUG_ON(fdt->fd[fd] != NULL); rcu_assign_pointer(fdt->fd[fd], file); spin_unlock(&files->file_lock); return; @@ -655,7 +656,7 @@ void fd_install(unsigned int fd, struct file *file) /* coupled with smp_wmb() in expand_fdtable() */ smp_rmb(); fdt = rcu_dereference_sched(files->fdt); - BUG_ON(fdt->fd[fd] != NULL); + VFS_BUG_ON(fdt->fd[fd] != NULL); rcu_assign_pointer(fdt->fd[fd], file); rcu_read_unlock_sched(); }
This also restores the check which got removed in 52732bb9abc9ee5b ("fs/file.c: remove sanity_check and add likely/unlikely in alloc_fd()") for performance reasons -- they no longer apply with a debug-only variant. Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> --- I have about 0 opinion whether this should be BUG or WARN, the code was already inconsistent on this front. If you want the latter, I'll have 0 complaints if you just sed it and commit as yours. This reminded me to sort out that litmus test for smp_rmb, hopefully soon(tm) as it is now nagging me. fs/file.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)