From: Dave Chinner dchinner@redhat.com
mainline inclusion from mainline-v6.4-rc6 commit 0853b5de42b471a92f4ff128a8757b87427d2431 category: bugfix bugzilla: 188883, https://gitee.com/openeuler/kernel/issues/I76JSK CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Extent freeing neeeds to be able to avoid a busy extent deadlock when the transaction itself holds the only busy extents in the allocation group. This may occur if we have an EFI that contains multiple extents to be freed, and the freeing the second intent requires the space the first extent free released to expand the AGFL. If we block on the busy extent at this point, we deadlock.
We hold a dirty transaction that contains a entire atomic extent free operations within it, so if we can abort the extent free operation and commit the progress that we've made, the busy extent can be resolved by a log force. Hence we can restart the aborted extent free with a new transaction and continue to make progress without risking deadlocks.
To enable this, we need the EFI processing code to be able to handle an -EAGAIN error to tell it to commit the current transaction and retry again. This mechanism is already built into the defer ops processing (used bythe refcount btree modification intents), so there's relatively little handling we need to add to the EFI code to enable this.
Signed-off-by: Dave Chinner dchinner@redhat.com Reviewed-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Chandan Babu R chandan.babu@oracle.com Signed-off-by: Long Li leo.lilong@huawei.com
Conflicts: fs/xfs/xfs_extfree_item.c --- fs/xfs/xfs_extfree_item.c | 68 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 67 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c index c9c648a618d6..24ff79d1a123 100644 --- a/fs/xfs/xfs_extfree_item.c +++ b/fs/xfs/xfs_extfree_item.c @@ -352,6 +352,34 @@ xfs_trans_get_efd( return efdp; }
+/* + * Fill the EFD with all extents from the EFI when we need to roll the + * transaction and continue with a new EFI. + * + * This simply copies all the extents in the EFI to the EFD rather than make + * assumptions about which extents in the EFI have already been processed. We + * currently keep the xefi list in the same order as the EFI extent list, but + * that may not always be the case. Copying everything avoids leaving a landmine + * were we fail to cancel all the extents in an EFI if the xefi list is + * processed in a different order to the extents in the EFI. + */ +static void +xfs_efd_from_efi( + struct xfs_efd_log_item *efdp) +{ + struct xfs_efi_log_item *efip = efdp->efd_efip; + uint i; + + ASSERT(efip->efi_format.efi_nextents > 0); + ASSERT(efdp->efd_next_extent < efip->efi_format.efi_nextents); + + for (i = 0; i < efip->efi_format.efi_nextents; i++) { + efdp->efd_format.efd_extents[i] = + efip->efi_format.efi_extents[i]; + } + efdp->efd_next_extent = efip->efi_format.efi_nextents; +} + /* * Free an extent and log it to the EFD. Note that the transaction is marked * dirty regardless of whether the extent free succeeds or fails to support the @@ -395,6 +423,17 @@ xfs_trans_free_extent( tp->t_flags |= XFS_TRANS_DIRTY; set_bit(XFS_LI_DIRTY, &efdp->efd_item.li_flags);
+ /* + * If we need a new transaction to make progress, the caller will log a + * new EFI with the current contents. It will also log an EFD to cancel + * the existing EFI, and so we need to copy all the unprocessed extents + * in this EFI to the EFD so this works correctly. + */ + if (error == -EAGAIN) { + xfs_efd_from_efi(efdp); + return error; + } + next_extent = efdp->efd_next_extent; ASSERT(next_extent < efdp->efd_format.efd_nextents); extp = &(efdp->efd_format.efd_extents[next_extent]); @@ -492,6 +531,14 @@ xfs_extent_free_finish_item( free = container_of(item, struct xfs_extent_free_item, xefi_list);
error = xfs_trans_free_extent(tp, EFD_ITEM(done), free); + + /* + * Don't free the XEFI if we need a new transaction to complete + * processing of it. + */ + if (error == -EAGAIN) + return error; + kmem_cache_free(xfs_extfree_item_cache, free); return error; } @@ -606,6 +653,7 @@ xfs_efi_item_recover( xfs_fsblock_t startblock_fsb; int i; int error = 0; + bool requeue_only = false;
/* * First check the validity of the extents described by the @@ -639,7 +687,25 @@ xfs_efi_item_recover( fake.xefi_startblock = extp->ext_start; fake.xefi_blockcount = extp->ext_len;
- error = xfs_trans_free_extent(tp, efdp, &fake); + if (!requeue_only) + error = xfs_trans_free_extent(tp, efdp, &fake); + + /* + * If we can't free the extent without potentially deadlocking, + * requeue the rest of the extents to a new so that they get + * run again later with a new transaction context. + */ + if (error == -EAGAIN || requeue_only) { + error = xfs_free_extent_later(tp, fake.xefi_startblock, + fake.xefi_blockcount, + &XFS_RMAP_OINFO_ANY_OWNER, + fake.xefi_agresv); + if (!error) { + requeue_only = true; + continue; + } + }; + if (error) goto abort_error;