linux-dev/fs/xfs, branch master

xfs: rename XFS_REFC_COW_START to _COWFLAG

2022-10-31T15:58:22Z

We've been (ab)using XFS_REFC_COW_START as both an integer quantity and a bit flag, even though it's *only* a bit flag. Rename the variable to reflect its nature and update the cast target since we're not supposed to be comparing it to xfs_agblock_t now. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: fix uninitialized list head in struct xfs_refcount_recovery

2022-10-31T15:58:22Z

We're supposed to initialize the list head of an object before adding it to another list. Fix that, and stop using the kmem_{alloc,free} calls from the Irix days. Fixes: 174edb0e46e5 ("xfs: store in-progress CoW allocations in the refcount btree") Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: fix agblocks check in the cow leftover recovery function

2022-10-31T15:58:21Z

As we've seen, refcount records use the upper bit of the rc_startblock field to ensure that all the refcount records are at the right side of the refcount btree. This works because an AG is never allowed to have more than (1U << 31) blocks in it. If we ever encounter a filesystem claiming to have that many blocks, we absolutely do not want reflink touching it at all. However, this test at the start of xfs_refcount_recover_cow_leftovers is slightly incorrect -- it /should/ be checking that agblocks isn't larger than the XFS_MAX_CRC_AG_BLOCKS constant, and it should check that the constant is never large enough to conflict with that CoW flag. Note that the V5 superblock verifier has not historically rejected filesystems where agblocks >= XFS_MAX_CRC_AG_BLOCKS, which is why this ended up in the COW recovery routine. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: check record domain when accessing refcount records

2022-10-31T15:58:21Z

Now that we've separated the startblock and CoW/shared extent domain in the incore refcount record structure, check the domain whenever we retrieve a record to ensure that it's still in the domain that we want. Depending on the circumstances, a change in domain either means we're done processing or that we've found a corruption and need to fail out. The refcount check in xchk_xref_is_cow_staging is redundant since _get_rec has done that for a long time now, so we can get rid of it. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: remove XFS_FIND_RCEXT_SHARED and _COW

2022-10-31T15:58:21Z

Now that we have an explicit enum for shared and CoW staging extents, we can get rid of the old FIND_RCEXT flags. Omit a couple of conversions that disappear in the next patches. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: refactor domain and refcount checking

2022-10-31T15:58:21Z

Create a helper function to ensure that CoW staging extent records have a single refcount and that shared extent records have more than 1 refcount. We'll put this to more use in the next patch. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: report refcount domain in tracepoints

2022-10-31T15:58:21Z

Now that we've broken out the startblock and shared/cow domain in the incore refcount extent record structure, update the tracepoints to report the domain. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: track cow/shared record domains explicitly in xfs_refcount_irec

2022-10-31T15:58:21Z

Just prior to committing the reflink code into upstream, the xfs maintainer at the time requested that I find a way to shard the refcount records into two domains -- one for records tracking shared extents, and a second for tracking CoW staging extents. The idea here was to minimize mount time CoW reclamation by pushing all the CoW records to the right edge of the keyspace, and it was accomplished by setting the upper bit in rc_startblock. We don't allow AGs to have more than 2^31 blocks, so the bit was free. Unfortunately, this was a very late addition to the codebase, so most of the refcount record processing code still treats rc_startblock as a u32 and pays no attention to whether or not the upper bit (the cow flag) is set. This is a weakness is theoretically exploitable, since we're not fully validating the incoming metadata records. Fuzzing demonstrates practical exploits of this weakness. If the cow flag of a node block key record is corrupted, a lookup operation can go to the wrong record block and start returning records from the wrong cow/shared domain. This causes the math to go all wrong (since cow domain is still implicit in the upper bit of rc_startblock) and we can crash the kernel by tricking xfs into jumping into a nonexistent AG and tripping over xfs_perag_get(mp, ) returning NULL. To fix this, start tracking the domain as an explicit part of struct xfs_refcount_irec, adjust all refcount functions to check the domain of a returned record, and alter the function definitions to accept them where necessary. Found by fuzzing keys[2].cowflag = add in xfs/464. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: refactor refcount record usage in xchk_refcountbt_rec

2022-10-31T15:58:21Z

Consolidate the open-coded xfs_refcount_irec fields into an actual struct and use the existing _btrec_to_irec to decode the ondisk record. This will reduce code churn in the next patch. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner

xfs: move _irec structs to xfs_types.h

2022-10-31T15:58:20Z

Structure definitions for incore objects do not belong in the ondisk format header. Move them to the incore types header where they belong. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner