lkml.org 
[lkml]   [2020]   [Mar]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: 5.5 XFS getdents regression?
Date
On Wed, 2020-03-11 at 18:22 +0100, hch@lst.de wrote:
> On Wed, Mar 11, 2020 at 05:06:16PM +0000, Rantala, Tommi T. (Nokia -
> FI/Espoo) wrote:
> > On Wed, 2020-03-11 at 09:14 +1100, Dave Chinner wrote:
> > > On Tue, Mar 10, 2020 at 08:45:58AM +0000, Rantala, Tommi T. (Nokia -
> > > FI/Espoo) wrote:
> > > > Hello,
> > > >
> > > > One of my GitLab CI jobs stopped working after upgrading server
> > > > 5.4.18-
> > > > 100.fc30.x86_64 -> 5.5.7-100.fc30.x86_64.
> > > > (tested 5.5.8-100.fc30.x86_64 too, no change)
> > > > The server is fedora30 with XFS rootfs.
> > > > The problem reproduces always, and takes only couple minutes to
> > > > run.
> > > >
> > > > The CI job fails in the beginning when doing "git clean" in docker
> > > > container, and failing to rmdir some directory:
> > > > "warning: failed to remove
> > > > .vendor/pkg/mod/golang.org/x/net@v0.0.0-20200114155413-6afb5195e5aa/in
> > > > tern
> > > > al/socket: Directory not empty"
> > > >
> > > > Quick google search finds some other people reporting similar
> > > > problems
> > > > with 5.5.0:
> > > > https://gitlab.com/gitlab-org/gitlab-runner/issues/3185
> > >
> > > Which appears to be caused by multiple gitlab processes modifying
> > > the directory at the same time. i.e. something is adding an entry to
> > > the directory at the same time something is trying to rm -rf it.
> > > That's a race condition, and would lead to the exact symptoms you
> > > see here, depending on where in the directory the new entry is
> > > added.
> >
> > OK traced "execve" with strace too, and it shows that it's "git clean
> > -ffdx" command (single process) that is being executed in the
> > container,
> > which is doing the cleanup.
> >
> > Tested with 5.6-rc5, it's failing the same way.
> >
> > Spent some time to bisect this, and the problem is introduced by this:
> >
> > commit 263dde869bd09b1a709fd92118c7fff832773689
> > Author: Christoph Hellwig <hch@lst.de>
> > Date: Fri Nov 8 15:05:32 2019 -0800
> >
> > xfs: cleanup xfs_dir2_block_getdents
> >
> > Use an offset as the main means for iteration, and only do pointer
> > arithmetics to find the data/unused entries.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> >
> >
> >
> > Hmmmmm, looking at that commit, I think it slighty changed how the
> > "offset" is used compared to how the pointers were used.
> >
> > This cures the issue for me, tested (briefly) on top of 5.6-rc5.
> > Does it make sense...?
> > (Email client probably damages white-space, sorry, I'll send this
> > properly
> > signed-off with git-send-email if it's OK)
>
> Thanks, this looks good. Although I wonder if the slightly different
> version below might be a little more elegant?

Yes that's better indeed, thanks!
-Tommi


> diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c
> index 0d3b640cf1cc..871ec22c9aee 100644
> --- a/fs/xfs/xfs_dir2_readdir.c
> +++ b/fs/xfs/xfs_dir2_readdir.c
> @@ -147,7 +147,7 @@ xfs_dir2_block_getdents(
> xfs_off_t cook;
> struct xfs_da_geometry *geo = args->geo;
> int lock_mode;
> - unsigned int offset;
> + unsigned int offset, next_offset;
> unsigned int end;
>
> /*
> @@ -173,9 +173,10 @@ xfs_dir2_block_getdents(
> * Loop over the data portion of the block.
> * Each object is a real entry (dep) or an unused one (dup).
> */
> - offset = geo->data_entry_offset;
> end = xfs_dir3_data_end_offset(geo, bp->b_addr);
> - while (offset < end) {
> + for (offset = geo->data_entry_offset;
> + offset < end;
> + offset = next_offset) {
> struct xfs_dir2_data_unused *dup = bp->b_addr +
> offset;
> struct xfs_dir2_data_entry *dep = bp->b_addr +
> offset;
> uint8_t filetype;
> @@ -184,14 +185,15 @@ xfs_dir2_block_getdents(
> * Unused, skip it.
> */
> if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
> - offset += be16_to_cpu(dup->length);
> + next_offset = offset + be16_to_cpu(dup->length);
> continue;
> }
>
> /*
> * Bump pointer for the next iteration.
> */
> - offset += xfs_dir2_data_entsize(dp->i_mount, dep-
> >namelen);
> + next_offset = offset +
> + xfs_dir2_data_entsize(dp->i_mount, dep->namelen);
>
> /*
> * The entry is before the desired starting point, skip
> it.

\
 
 \ /
  Last update: 2020-03-12 09:10    [W:0.078 / U:0.336 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site