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author | Darrick J. Wong <darrick.wong@oracle.com> | 2018-05-05 01:30:19 +0300 |
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committer | Darrick J. Wong <darrick.wong@oracle.com> | 2018-05-10 18:56:47 +0300 |
commit | 7b6b50f55c1064e619f2da0696ed99f9db10b960 (patch) | |
tree | 141b3a966adcb0249c9f81d7c217a6c53fdf932e /fs/xfs/xfs_dquot.c | |
parent | 84ca484ecf2f8e1dc3afddc895cb9b62c531db49 (diff) | |
download | linux-7b6b50f55c1064e619f2da0696ed99f9db10b960.tar.xz |
xfs: release new dquot buffer on defer_finish error
In commit efa092f3d4c6 "[XFS] Fixes a bug in the quota code when
allocating a new dquot record", we allocate a new dquot block, grab a
buffer to initialize it, and return the locked initialized dquot buffer
to the caller for further in-core dquot initialization. Unfortunately,
if the _bmap_finish errored out, _qm_dqalloc would also error out
without bothering to free the (locked) buffer. Leaking a locked buffer
caused hangs in generic/388 when quotas are enabled.
Furthermore, the _bmap_finish -> _defer_finish conversion in
310a75a3c6c747 ("xfs: change xfs_bmap_{finish,cancel,init,free} ->
xfs_defer_*") failed to observe that the buffer was held going into
_defer_finish and therefore failed to notice that the buffer lock is
/not/ maintained afterwards. Now that we can bjoin a buffer to a
defer_ops, use this mechanism to ensure that the buffer stays locked
across the _defer_finish. Release the holds and locks on the buffer as
appropriate if we have to error out.
There is a subtlety here for the caller in that the buffer emerges
locked and held to the transaction, so if the _trans_commit fails we
have to release the buffer explicitly. This fixes the unmount hang
in generic/388 when quotas are enabled.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Diffstat (limited to 'fs/xfs/xfs_dquot.c')
-rw-r--r-- | fs/xfs/xfs_dquot.c | 48 |
1 files changed, 28 insertions, 20 deletions
diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c index 4ca9c39879ae..32d7359b3c18 100644 --- a/fs/xfs/xfs_dquot.c +++ b/fs/xfs/xfs_dquot.c @@ -362,32 +362,40 @@ xfs_qm_dqalloc( dqp->dq_flags & XFS_DQ_ALLTYPES, bp); /* - * xfs_defer_finish() may commit the current transaction and - * start a second transaction if the freelist is not empty. + * Hold the buffer and join it to the dfops so that we'll still own + * the buffer when we return to the caller. The buffer disposal on + * error must be paid attention to very carefully, as it has been + * broken since commit efa092f3d4c6 "[XFS] Fixes a bug in the quota + * code when allocating a new dquot record" in 2005, and the later + * conversion to xfs_defer_ops in commit 310a75a3c6c747 failed to keep + * the buffer locked across the _defer_finish call. We can now do + * this correctly with xfs_defer_bjoin. * - * Since we still want to modify this buffer, we need to - * ensure that the buffer is not released on commit of - * the first transaction and ensure the buffer is added to the - * second transaction. + * Above, we allocated a disk block for the dquot information and + * used get_buf to initialize the dquot. If the _defer_bjoin fails, + * the buffer is still locked to *tpp, so we must _bhold_release and + * then _trans_brelse the buffer. If the _defer_finish fails, the old + * transaction is gone but the new buffer is not joined or held to any + * transaction, so we must _buf_relse it. * - * If there is only one transaction then don't stop the buffer - * from being released when it commits later on. + * If everything succeeds, the caller of this function is returned a + * buffer that is locked and joined to the transaction. The caller + * is responsible for unlocking any buffer passed back, either + * manually or by committing the transaction. */ - - xfs_trans_bhold(tp, bp); - + xfs_trans_bhold(*tpp, bp); + error = xfs_defer_bjoin(&dfops, bp); + if (error) { + xfs_trans_bhold_release(*tpp, bp); + xfs_trans_brelse(*tpp, bp); + goto error1; + } error = xfs_defer_finish(tpp, &dfops); - if (error) + if (error) { + xfs_buf_relse(bp); goto error1; - - /* Transaction was committed? */ - if (*tpp != tp) { - tp = *tpp; - xfs_trans_bjoin(tp, bp); - } else { - xfs_trans_bhold_release(tp, bp); } - + xfs_trans_bhold_release(*tpp, bp); *O_bpp = bp; return 0; |