[review please] Re: DMAPI problem with the new filldir implementation

David Chinner
2007-12-10T21:55:16Z

This passes xfsqa and various other handrolled tests I've thrown
at it. Can i get some eyeballs on this, please?

Cheers,

Dave.

On Fri, Dec 07, 2007 at 12:49:40PM +1100, David Chinner wrote:
> On Fri, Dec 07, 2007 at 11:29:22AM +1100, David Chinner wrote:
> > (cc xfs-dev and xfs@oss)
> >
> > On Fri, Dec 07, 2007 at 09:38:19AM +1100, Vlad Apostolov wrote:
> > > Hi Christoph and Dave,
> > >
> > > It looks like we may have a problem caused by this patch:
> > >
> > > http://oss.sgi.com/archives/xfs/2007-07/msg00338.html
> > >
> > > It makes XFS test 144 to fail if the inode size is 2k. I did
> > > some investigation and I think xfs_readdir() returns incorrect
> > > next location for shortform directories. When the inode size is
> > > 2k, more dir entries fit inline in the inode and test 144
> > > dm_get_dirattrs() starts using the shortform.
> > >
> > > I think this code here
> > >
> > > if (filldir(dirent, sfep->name, sfep->namelen,
> > > off + xfs_dir2_data_entsize(sfep->namelen),
> > > ino, DT_UNKNOWN)) {
> > >
> > > adds some offset "xfs_dir2_data_entsize(sfep->namelen)" to the
> > > next location pointer, which appears to be incorrect and causes
> > > directory entries to be skipped on the next call of dm_get_dirattrs().
> >
> > It's supposed to be the offset of the next dirent:
> >
> > On Linux, the dirent structure is defined as follows:
> >
> > struct dirent {
> > ino_t d_ino; /* inode number */
> > >>>>>> off_t d_off; /* offset to the next dirent */
> > unsigned short d_reclen; /* length of this record */
> > unsigned char d_type; /* type of file */
> > char d_name[256]; /* filename */
> > };
> >
> > However, looking at the generic filldir() implementation in fs/readdir.c,
> > I see that it:
> >
> > dirent = buf->previous;
> > if (dirent) {
> > if (__put_user(offset, &dirent->d_off))
> > goto efault;
> > }
> >
> > Puts the offset in the *previous* dirent, not the current one. That
> > means that the three calls to XFs makes to filldir() are all incorrect;
> > they should be passing the offset of the current object, not the next
> > object as teh filldir code stuffs it in the previous dirent.
> >
> > The reason that dmapi is failing here is that it uses teh offset as the
> > cookie to to indicate the next inode to read. However, getdents uses the
> > filp->f_pos:
> >
> > error = vfs_readdir(file, filldir, &buf);
> > if (error < 0)
> > goto out_putf;
> > error = buf.error;
> > lastdirent = buf.previous;
> > if (lastdirent) {
> > if (put_user(file->f_pos, &lastdirent->d_off))
> > error = -EFAULT;
> > else
> > error = count - buf.count;
> > }
> >
> > and xfs_file_readdir uses that as teh offset for lookups and keeps it up
> > to date correctly. hence the getdents code is overwritting the incorrect
> > value XFS has been stuffing in there and hence we haven't seen this
> > on normal syscalls.
>
> Except that the hack to go back to double buffering relies on the
> filldir offset being pushed off to be the next dirent, and hence
> with the patch I sent we set filp->f_pos incorrectly in
> xfs_file_readdir().....
>
> <sigh>
>
> > Ok, patch attached. passes 144 on all inode sizes, otherwise mostly
> > untested.
>
> I did say mostly untested :/
>
> Updated patch below (which passes 006 but is still mostly untested).
>
> Cheers,
>
> dave.
> --
> Dave Chinner
> Principal Engineer
> SGI Australian Software Group
>
> ---
> fs/xfs/dmapi/xfs_dm.c | 4 ----
> fs/xfs/linux-2.6/xfs_file.c | 4 ++--
> fs/xfs/xfs_dir2_block.c | 6 ++----
> fs/xfs/xfs_dir2_leaf.c | 2 +-
> fs/xfs/xfs_dir2_sf.c | 9 +++------
> 5 files changed, 8 insertions(+), 17 deletions(-)
>
> Index: 2.6.x-xfs-new/fs/xfs/xfs_dir2_block.c
> ===================================================================
> --- 2.6.x-xfs-new.orig/fs/xfs/xfs_dir2_block.c 2007-08-23 23:03:09.000000000 +1000
> +++ 2.6.x-xfs-new/fs/xfs/xfs_dir2_block.c 2007-12-07 10:23:14.933645761 +1100
> @@ -508,7 +508,7 @@ xfs_dir2_block_getdents(
> continue;
>
> cook = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
> - ptr - (char *)block);
> + (char *)dep - (char *)block);
> ino = be64_to_cpu(dep->inumber);
> #if XFS_BIG_INUMS
> ino += mp->m_inoadd;
> @@ -519,9 +519,7 @@ xfs_dir2_block_getdents(
> */
> if (filldir(dirent, dep->name, dep->namelen, cook,
> ino, DT_UNKNOWN)) {
> - *offset = xfs_dir2_db_off_to_dataptr(mp,
> - mp->m_dirdatablk,
> - (char *)dep - (char *)block);
> + *offset = cook;
> xfs_da_brelse(NULL, bp);
> return 0;
> }
> Index: 2.6.x-xfs-new/fs/xfs/xfs_dir2_leaf.c
> ===================================================================
> --- 2.6.x-xfs-new.orig/fs/xfs/xfs_dir2_leaf.c 2007-08-24 22:24:45.000000000 +1000
> +++ 2.6.x-xfs-new/fs/xfs/xfs_dir2_leaf.c 2007-12-07 10:18:17.623544813 +1100
> @@ -1091,7 +1091,7 @@ xfs_dir2_leaf_getdents(
> * Won't fit. Return to caller.
> */
> if (filldir(dirent, dep->name, dep->namelen,
> - xfs_dir2_byte_to_dataptr(mp, curoff + length),
> + xfs_dir2_byte_to_dataptr(mp, curoff),
> ino, DT_UNKNOWN))
> break;
>
> Index: 2.6.x-xfs-new/fs/xfs/xfs_dir2_sf.c
> ===================================================================
> --- 2.6.x-xfs-new.orig/fs/xfs/xfs_dir2_sf.c 2007-08-23 23:03:09.000000000 +1000
> +++ 2.6.x-xfs-new/fs/xfs/xfs_dir2_sf.c 2007-12-07 10:20:57.887115812 +1100
> @@ -752,7 +752,7 @@ xfs_dir2_sf_getdents(
> #if XFS_BIG_INUMS
> ino += mp->m_inoadd;
> #endif
> - if (filldir(dirent, ".", 1, dotdot_offset, ino, DT_DIR)) {
> + if (filldir(dirent, ".", 1, dot_offset, ino, DT_DIR)) {
> *offset = dot_offset;
> return 0;
> }
> @@ -762,13 +762,11 @@ xfs_dir2_sf_getdents(
> * Put .. entry unless we're starting past it.
> */
> if (*offset <= dotdot_offset) {
> - off = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
> - XFS_DIR2_DATA_FIRST_OFFSET);
> ino = xfs_dir2_sf_get_inumber(sfp, &sfp->hdr.parent);
> #if XFS_BIG_INUMS
> ino += mp->m_inoadd;
> #endif
> - if (filldir(dirent, "..", 2, off, ino, DT_DIR)) {
> + if (filldir(dirent, "..", 2, dotdot_offset, ino, DT_DIR)) {
> *offset = dotdot_offset;
> return 0;
> }
> @@ -793,8 +791,7 @@ xfs_dir2_sf_getdents(
> #endif
>
> if (filldir(dirent, sfep->name, sfep->namelen,
> - off + xfs_dir2_data_entsize(sfep->namelen),
> - ino, DT_UNKNOWN)) {
> + off, ino, DT_UNKNOWN)) {
> *offset = off;
> return 0;
> }
> Index: 2.6.x-xfs-new/fs/xfs/dmapi/xfs_dm.c
> ===================================================================
> --- 2.6.x-xfs-new.orig/fs/xfs/dmapi/xfs_dm.c 2007-12-03 17:11:46.000000000 +1100
> +++ 2.6.x-xfs-new/fs/xfs/dmapi/xfs_dm.c 2007-12-07 11:25:42.678472255 +1100
> @@ -1772,7 +1772,6 @@ xfs_dm_get_dioinfo(
>
> typedef struct dm_readdir_cb {
> xfs_mount_t *mp;
> - xfs_off_t lastoff;
> char __user *ubuf;
> dm_stat_t __user *lastbuf;
> size_t spaceleft;
> @@ -1834,7 +1833,6 @@ dm_filldir(void *__buf, const char *name
> cb->spaceleft -= statp->_link;
> cb->nwritten += statp->_link;
> cb->ubuf += statp->_link;
> - cb->lastoff = offset;
>
> return 0;
>
> @@ -1910,8 +1908,6 @@ xfs_dm_get_dirattrs_rvp(
> goto out_kfree;
> }
>
> - loc = cb->lastoff;
> -
> error = -EFAULT;
> if (cb->lastbuf && put_user(0, &cb->lastbuf->_link))
> goto out_kfree;
> Index: 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_file.c
> ===================================================================
> --- 2.6.x-xfs-new.orig/fs/xfs/linux-2.6/xfs_file.c 2007-12-03 18:41:26.000000000 +1100
> +++ 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_file.c 2007-12-07 12:36:52.123061435 +1100
> @@ -357,13 +357,13 @@ xfs_file_readdir(
>
> reclen = sizeof(struct hack_dirent) + de->namlen;
> size -= reclen;
> - curr_offset = de->offset /* & 0x7fffffff */;
> de = (struct hack_dirent *)((char *)de + reclen);
> + curr_offset = de->offset /* & 0x7fffffff */;
> }
> }
>
> done:
> - if (!error) {
> + if (!error) {
> if (size == 0)
> filp->f_pos = offset & 0x7fffffff;
> else if (de)