Thanks Eric,
I'll update the title.
We are using the frag command to quickly scan the file system and
obtain info such as file size distribution and overheads. I'll send
that change out for review soon :)
Hopefully that will make the frag command great again! :D
On Fri, Apr 26, 2019 at 5:13 PM Eric Sandeen <sandeen@xxxxxxxxxxx> wrote:
>
> On 4/26/19 5:59 PM, Jorge Guerra wrote:
> > From: Jorge Guerra <jorgeguerra@xxxxxx>
> >
> > While running the 'frag' command of 'xfs_db' we noticed that the
> > tool is not scanning all the files in the file system. We noticed
> > this when we modified the tool to print the inodes of all the files
> > scanned. For example:
> >
> > $ find /mnt/xfsdisk -type f | wc -l
> > 1782674
> > $ xfs_db -r -c frag /dev/sdXX | grep MB | awk '{print $5}' | paste -s -d+ | bc
> > 656818
> >
> > Upon inspecting the code we noticed that the scanfunc_ino function
> > stops processing a given inode block once it encounters a free leaf.
> > However, in practice we see that inodes are necessarily always layed
> > out contiguously on the leaf node. This resulted in the 'frag'
> > command skipping some valid inodes.
> >
> > In this change we modify the scanfunc_ino function to skip freed
> > inodes. With the change in place we ran the same experiment again
> > and noticed a more accurate file count:
> >
> > $ find /mnt/d0 -type f | wc -l
> > 1810442
> > $ xfs_db -r -c frag /dev/sdXX | grep MB | awk '{print $5}' | paste -s -d+ | bc
> > 1810442
> >
> > Signed-off-by: Jorge Guerra <jorgeguerra@xxxxxx>
>
> This looks right, but I'll warn you that xfs_db's frag command is largely
> useless in the first place. ;)
>
> Also, I think:
>
> Fixes: 2a5eb70c ("xfs_db: teach the frag command about sparse inode chunks")
>
> Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>
> Thanks!
>
> > ---
> > db/frag.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/db/frag.c b/db/frag.c
> > index 5f33cb73..91395234 100644
> > --- a/db/frag.c
> > +++ b/db/frag.c
> > @@ -507,7 +507,7 @@ scanfunc_ino(
> >
> > for (j = 0; j < inodes_per_buf; j++) {
> > if (XFS_INOBT_IS_FREE_DISK(&rp[i], ioff + j))
> > - goto next_buf;
> > + continue;
> > dip = (xfs_dinode_t *)((char *)iocur_top->data +
> > ((off + j) << mp->m_sb.sb_inodelog));
> > process_inode(agf, agino + ioff + j, dip);
> >
--
Jorge E Guerra D
