Re: [LTP] [PATCH 4/4] libswap: add Btrfs noCOW attribute setting for swap files

Li Wang
2024-01-22T09:04:44Z

Hi Petr,

On Mon, Jan 22, 2024 at 4:40 PM Petr Vorel <pvorel@suse.cz> wrote:

> Hi Li,
>
> > The patch aims to ensure swap files on Btrfs filesystems are created
> > with the appropriate FS_NOCOW_FL attribute, which is necessary to
> > disable CoW (Copy-on-Write) for swap files, perthe btrfs(5) manual page.
> > This change is gated behind a kernel version check to ensure
> compatibility
> > with the system's capabilities.
>
> > Signed-off-by: Li Wang <liwang@redhat.com>
> > ---
> > libs/libltpswap/libswap.c | 35 +++++++++++++++++++++++++++++++++++
> > 1 file changed, 35 insertions(+)
>
> > diff --git a/libs/libltpswap/libswap.c b/libs/libltpswap/libswap.c
> > index 623f2fb3c..0b1d9a227 100644
> > --- a/libs/libltpswap/libswap.c
> > +++ b/libs/libltpswap/libswap.c
> > @@ -4,6 +4,7 @@
> > * Author: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
> > */
>
> > +#include <linux/fs.h>
> > #include <errno.h>
>
> > #define TST_NO_DEFAULT_MAIN
> > @@ -23,11 +24,37 @@ static const char *const swap_supported_fs[] = {
> > NULL
> > };
>
> > +static void set_nocow_attr(const char *filename)
> > +{
> > + int fd;
> > + int attrs;
> > +
> > + fd = SAFE_OPEN(filename, O_RDONLY);
> > +
> > + if (ioctl(fd, FS_IOC_GETFLAGS, &attrs) == -1) {
> > + tst_res(TFAIL | TERRNO, "Error getting attributes");
> I guess we don't want to break all testing due ioctl failure, right?
> Otherwise I would use SAFE_IOCTL().
>

+1, thanks.

> > + close(fd);
> > + return;
> > + }
> > +
> > + attrs |= FS_NOCOW_FL;
> > +
> > + if (ioctl(fd, FS_IOC_SETFLAGS, &attrs) == -1)
> > + tst_res(TFAIL | TERRNO, "Error setting FS_NOCOW_FL
> attribute");
> And here as well.
>

+1

> > + else
> > + tst_res(TINFO, "FS_NOCOW_FL attribute set on %s\n",
> filename);
> This is redundant new line, please remove \n before merging.
>

+1, I would send a V2 for 4/4, because I found additional issue
that the "btrfs" should be added in swap_supported_fs[] as well.

> nit: make check reports various of formatting issues (on master there are
> only
> two). Would you dare to fix them? (some of them are added in the first
> commit).
>

+1

> make check-libswap
> CHECK libs/libltpswap/libswap.c
> libswap.c:75: WARNING: Missing a blank line after declarations
> libswap.c:101: WARNING: please, no spaces at the start of a line
> libswap.c:102: WARNING: Missing a blank line after declarations
> libswap.c:102: WARNING: please, no spaces at the start of a line
> libswap.c:102: WARNING: suspect code indent for conditional statements (7,
> 15)
> libswap.c:103: ERROR: code indent should use tabs where possible
> libswap.c:103: WARNING: please, no spaces at the start of a line
> libswap.c:103: WARNING: suspect code indent for conditional statements
> (15, 23)
> libswap.c:104: ERROR: code indent should use tabs where possible
> libswap.c:104: WARNING: please, no spaces at the start of a line
> libswap.c:105: ERROR: code indent should use tabs where possible
> libswap.c:105: WARNING: please, no spaces at the start of a line
> libswap.c:105: WARNING: suspect code indent for conditional statements
> (15, 23)
> libswap.c:106: ERROR: code indent should use tabs where possible
> libswap.c:106: WARNING: please, no spaces at the start of a line
> libswap.c:107: WARNING: please, no spaces at the start of a line
>
>
> > +
> > + close(fd);
> > +}
> > +
> > /*
> > * Make a swap file
> > */
> > int make_swapfile(const char *swapfile, int safe)
> > {
> > + long fs_type = tst_fs_type(swapfile);
> > + const char *fstype = tst_fs_type_name(fs_type);
> > +
> > if (!tst_fs_has_free(".", sysconf(_SC_PAGESIZE) * 10, TST_BYTES))
> > tst_brk(TBROK, "Insufficient disk space to create swap
> file");
>
> > @@ -35,6 +62,14 @@ int make_swapfile(const char *swapfile, int safe)
> > if (tst_fill_file(swapfile, 0, sysconf(_SC_PAGESIZE), 10) != 0)
> > tst_brk(TBROK, "Failed to create swapfile");
>
> > + /* Btrfs file need set 'nocow' attribute */
> > + if (strcmp(fstype, "btrfs") == 0) {
>
> Maybe using just fs_type (long), i.e. avoid conversion to char * via
> tst_fs_type_name()? Or am I missing something?
>
> long fs_type = tst_fs_type(swapfile);
> ...
> if (fs_type == TST_BTRFS_MAGIC) {
>

Good point.

>
> Kind regards,
> Petr
>
> > + if (tst_kvercmp(5, 0, 0) > 0)
> > + set_nocow_attr(swapfile);
> > + else
> > + tst_brk(TCONF, "Swapfile on %s not implemented",
> fstype);
> > + }
> > +
> > /* make the file swapfile */
> > const char *argv[2 + 1];
> > argv[0] = "mkswap";
>
>

--
Regards,
Li Wang