From: "Darrick J. Wong" <djwong@kernel.org>
To: aalbersh@redhat.com, ebiggers@kernel.org, cem@kernel.org,
djwong@kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
fsverity@lists.linux.dev
Subject: [PATCH 12/38] xfs: use merkle tree offset as attr hash
Date: Mon, 29 Apr 2024 20:34:00 -0700 [thread overview]
Message-ID: <171444683296.960383.5604207199115455905.stgit@frogsfrogsfrogs> (raw)
In-Reply-To: <171444683053.960383.12871831441554683674.stgit@frogsfrogsfrogs>
From: Darrick J. Wong <djwong@kernel.org>
I was exploring the fsverity metadata with xfs_db after creating a 220MB
verity file, and I noticed the following in the debugger output:
entries[0-75] = [hashval,nameidx,incomplete,root,secure,local,parent,verity]
0:[0,4076,0,0,0,0,0,1]
1:[0,1472,0,0,0,1,0,1]
2:[0x800,4056,0,0,0,0,0,1]
3:[0x800,4036,0,0,0,0,0,1]
...
72:[0x12000,2716,0,0,0,0,0,1]
73:[0x12000,2696,0,0,0,0,0,1]
74:[0x12800,2676,0,0,0,0,0,1]
75:[0x12800,2656,0,0,0,0,0,1]
...
nvlist[0].merkle_off = 0x18000
nvlist[1].merkle_off = 0
nvlist[2].merkle_off = 0x19000
nvlist[3].merkle_off = 0x1000
...
nvlist[71].merkle_off = 0x5b000
nvlist[72].merkle_off = 0x44000
nvlist[73].merkle_off = 0x5c000
nvlist[74].merkle_off = 0x45000
nvlist[75].merkle_off = 0x5d000
Within just this attr leaf block, there are 76 attr entries, but only 38
distinct hash values. There are 415 merkle tree blocks for this file,
but we already have hash collisions. This isn't good performance from
the standard da hash function because we're mostly shifting and rolling
zeroes around.
However, we don't even have to do that much work -- the merkle tree
block keys are themslves u64 values. Truncate that value to 32 bits
(the size of xfs_dahash_t) and use that for the hash. We won't have any
collisions between merkle tree blocks until that tree grows to 2^32nd
blocks. On a 4k block filesystem, we won't hit that unless the file
contains more than 2^49 bytes, assuming sha256.
As a side effect, the keys for merkle tree blocks get written out in
roughly sequential order, though I didn't observe any change in
performance.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
---
libxfs/xfs_attr.c | 2 ++
libxfs/xfs_da_format.h | 6 ++++++
libxfs/xfs_verity.c | 16 ++++++++++++++++
libxfs/xfs_verity.h | 1 +
4 files changed, 25 insertions(+)
diff --git a/libxfs/xfs_attr.c b/libxfs/xfs_attr.c
index 94c425b984d2..2f491d072294 100644
--- a/libxfs/xfs_attr.c
+++ b/libxfs/xfs_attr.c
@@ -461,6 +461,8 @@ xfs_attr_hashval(
if (attr_flags & XFS_ATTR_PARENT)
return xfs_parent_hashattr(mp, name, namelen, value, valuelen);
+ if (attr_flags & XFS_ATTR_VERITY)
+ return xfs_verity_hashname(name, namelen);
return xfs_attr_hashname(name, namelen);
}
diff --git a/libxfs/xfs_da_format.h b/libxfs/xfs_da_format.h
index 43e9d1f00a4a..c95e8ca22daa 100644
--- a/libxfs/xfs_da_format.h
+++ b/libxfs/xfs_da_format.h
@@ -943,4 +943,10 @@ struct xfs_merkle_key {
#define XFS_VERITY_DESCRIPTOR_NAME "vdesc"
#define XFS_VERITY_DESCRIPTOR_NAME_LEN (sizeof(XFS_VERITY_DESCRIPTOR_NAME) - 1)
+/*
+ * Merkle tree blocks cannot be smaller than 1k in size, so the hash function
+ * can right-shift the merkle offset by this amount without losing anything.
+ */
+#define XFS_VERITY_HASH_SHIFT (10)
+
#endif /* __XFS_DA_FORMAT_H__ */
diff --git a/libxfs/xfs_verity.c b/libxfs/xfs_verity.c
index 8d1a759f995b..907a0e0fcf41 100644
--- a/libxfs/xfs_verity.c
+++ b/libxfs/xfs_verity.c
@@ -56,3 +56,19 @@ xfs_verity_namecheck(
return true;
}
+
+/*
+ * Compute name hash for a verity attribute. For merkle tree blocks, we want
+ * to use the merkle tree block offset as the hash value to avoid collisions
+ * between blocks unless the merkle tree becomes larger than 2^32 blocks.
+ */
+xfs_dahash_t
+xfs_verity_hashname(
+ const uint8_t *name,
+ unsigned int namelen)
+{
+ if (namelen != sizeof(struct xfs_merkle_key))
+ return xfs_attr_hashname(name, namelen);
+
+ return xfs_merkle_key_from_disk(name, namelen) >> XFS_VERITY_HASH_SHIFT;
+}
diff --git a/libxfs/xfs_verity.h b/libxfs/xfs_verity.h
index 5813665c5a01..3d7485c511d5 100644
--- a/libxfs/xfs_verity.h
+++ b/libxfs/xfs_verity.h
@@ -9,5 +9,6 @@ void xfs_merkle_key_to_disk(struct xfs_merkle_key *key, uint64_t pos);
uint64_t xfs_merkle_key_from_disk(const void *attr_name, int namelen);
bool xfs_verity_namecheck(unsigned int attr_flags, const void *name,
int namelen);
+xfs_dahash_t xfs_verity_hashname(const uint8_t *name, unsigned int namelen);
#endif /* __XFS_VERITY_H__ */
next prev parent reply other threads:[~2024-04-30 3:34 UTC|newest]
Thread overview: 165+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 3:11 [PATCHBOMB v5.6] fs-verity support for XFS Darrick J. Wong
2024-04-30 3:18 ` [PATCHSET v5.6 1/2] fs-verity: support merkle tree access by blocks Darrick J. Wong
2024-04-30 3:19 ` [PATCH 01/18] fs: add FS_XFLAG_VERITY for verity files Darrick J. Wong
2024-04-30 3:19 ` [PATCH 02/18] fsverity: pass tree_blocksize to end_enable_verity() Darrick J. Wong
2024-04-30 3:20 ` [PATCH 03/18] fsverity: convert verification to use byte instead of page offsets Darrick J. Wong
2024-05-01 7:33 ` Christoph Hellwig
2024-05-01 22:33 ` Darrick J. Wong
2024-05-02 0:42 ` Eric Biggers
2024-05-08 20:14 ` Darrick J. Wong
2024-04-30 3:20 ` [PATCH 04/18] fsverity: support block-based Merkle tree caching Darrick J. Wong
2024-05-01 7:36 ` Christoph Hellwig
2024-05-01 22:35 ` Darrick J. Wong
2024-05-02 4:42 ` Christoph Hellwig
2024-05-15 2:16 ` Eric Biggers
2024-04-30 3:20 ` [PATCH 05/18] fsverity: pass the merkle tree block level to fsverity_read_merkle_tree_block Darrick J. Wong
2024-04-30 3:20 ` [PATCH 06/18] fsverity: add per-sb workqueue for post read processing Darrick J. Wong
2024-04-30 3:21 ` [PATCH 07/18] fsverity: add tracepoints Darrick J. Wong
2024-04-30 3:21 ` [PATCH 08/18] fsverity: pass the new tree size and block size to ->begin_enable_verity Darrick J. Wong
2024-04-30 3:21 ` [PATCH 09/18] fsverity: expose merkle tree geometry to callers Darrick J. Wong
2024-04-30 3:22 ` [PATCH 10/18] fsverity: box up the write_merkle_tree_block parameters too Darrick J. Wong
2024-04-30 3:22 ` [PATCH 11/18] fsverity: pass the zero-hash value to the implementation Darrick J. Wong
2024-04-30 3:22 ` [PATCH 12/18] fsverity: report validation errors back to the filesystem Darrick J. Wong
2024-04-30 3:22 ` [PATCH 13/18] fsverity: pass super_block to fsverity_enqueue_verify_work Darrick J. Wong
2024-04-30 3:23 ` [PATCH 14/18] ext4: use a per-superblock fsverity workqueue Darrick J. Wong
2024-04-30 3:23 ` [PATCH 15/18] f2fs: " Darrick J. Wong
2024-04-30 3:23 ` [PATCH 16/18] btrfs: " Darrick J. Wong
2024-04-30 3:23 ` [PATCH 17/18] fsverity: remove system-wide workqueue Darrick J. Wong
2024-04-30 3:24 ` [PATCH 18/18] iomap: integrate fs-verity verification into iomap's read path Darrick J. Wong
2024-05-01 7:10 ` Christoph Hellwig
2024-05-01 22:37 ` Darrick J. Wong
2024-04-30 3:18 ` [PATCHSET v5.6 2/2] xfs: fs-verity support Darrick J. Wong
2024-04-30 3:24 ` [PATCH 01/26] xfs: use unsigned ints for non-negative quantities in xfs_attr_remote.c Darrick J. Wong
2024-05-01 6:55 ` Christoph Hellwig
2024-05-01 22:39 ` Darrick J. Wong
2024-05-02 4:56 ` Christoph Hellwig
2024-05-02 5:56 ` Chandan Babu R
2024-05-02 6:34 ` Christoph Hellwig
2024-04-30 3:24 ` [PATCH 02/26] xfs: turn XFS_ATTR3_RMT_BUF_SPACE into a function Darrick J. Wong
2024-05-01 6:55 ` Christoph Hellwig
2024-04-30 3:24 ` [PATCH 03/26] xfs: create a helper to compute the blockcount of a max sized remote value Darrick J. Wong
2024-05-01 6:56 ` Christoph Hellwig
2024-04-30 3:25 ` [PATCH 04/26] xfs: minor cleanups of xfs_attr3_rmt_blocks Darrick J. Wong
2024-05-01 6:56 ` Christoph Hellwig
2024-04-30 3:25 ` [PATCH 05/26] xfs: use an empty transaction to protect xfs_attr_get from deadlocks Darrick J. Wong
2024-05-01 6:57 ` Christoph Hellwig
2024-05-01 22:42 ` Darrick J. Wong
2024-04-30 3:25 ` [PATCH 06/26] xfs: add attribute type for fs-verity Darrick J. Wong
2024-04-30 3:25 ` [PATCH 07/26] xfs: do not use xfs_attr3_rmt_hdr for remote verity value blocks Darrick J. Wong
2024-04-30 3:26 ` [PATCH 08/26] xfs: add fs-verity ro-compat flag Darrick J. Wong
2024-04-30 3:26 ` [PATCH 09/26] xfs: add inode on-disk VERITY flag Darrick J. Wong
2024-04-30 3:26 ` [PATCH 10/26] xfs: initialize fs-verity on file open and cleanup on inode destruction Darrick J. Wong
2024-04-30 3:26 ` [PATCH 11/26] xfs: don't allow to enable DAX on fs-verity sealed inode Darrick J. Wong
2024-04-30 3:27 ` [PATCH 12/26] xfs: disable direct read path for fs-verity files Darrick J. Wong
2024-04-30 3:27 ` [PATCH 13/26] xfs: widen flags argument to the xfs_iflags_* helpers Darrick J. Wong
2024-05-01 6:54 ` Christoph Hellwig
2024-05-01 22:44 ` Darrick J. Wong
2024-04-30 3:27 ` [PATCH 14/26] xfs: add fs-verity support Darrick J. Wong
2024-04-30 3:28 ` [PATCH 15/26] xfs: create a per-mount shrinker for verity inodes merkle tree blocks Darrick J. Wong
2024-04-30 3:28 ` [PATCH 16/26] xfs: shrink verity blob cache Darrick J. Wong
2024-04-30 3:28 ` [PATCH 17/26] xfs: don't store trailing zeroes of merkle tree blocks Darrick J. Wong
2024-04-30 3:28 ` [PATCH 18/26] xfs: use merkle tree offset as attr hash Darrick J. Wong
2024-05-01 6:53 ` Christoph Hellwig
2024-05-01 7:23 ` Christoph Hellwig
2024-05-07 21:24 ` Darrick J. Wong
2024-05-08 11:47 ` Christoph Hellwig
2024-05-08 20:26 ` Darrick J. Wong
2024-05-09 5:02 ` Christoph Hellwig
2024-05-09 20:02 ` Darrick J. Wong
2024-05-10 5:08 ` Christoph Hellwig
2024-05-10 6:20 ` Christoph Hellwig
2024-05-17 17:17 ` Darrick J. Wong
2024-05-20 12:39 ` Christoph Hellwig
2024-05-20 16:02 ` Darrick J. Wong
2024-05-22 14:37 ` Christoph Hellwig
2024-05-22 18:29 ` Eric Biggers
2024-05-31 21:28 ` Darrick J. Wong
2024-05-31 21:45 ` Eric Biggers
2024-05-09 17:46 ` Eric Biggers
2024-05-09 18:04 ` Darrick J. Wong
2024-05-09 18:36 ` Eric Biggers
2024-04-30 3:29 ` [PATCH 19/26] xfs: don't bother storing merkle tree blocks for zeroed data blocks Darrick J. Wong
2024-05-01 6:47 ` Christoph Hellwig
2024-05-01 22:47 ` Darrick J. Wong
2024-05-02 0:01 ` Eric Biggers
2024-05-08 20:26 ` Darrick J. Wong
2024-04-30 3:29 ` [PATCH 20/26] xfs: add fs-verity ioctls Darrick J. Wong
2024-04-30 3:29 ` [PATCH 21/26] xfs: advertise fs-verity being available on filesystem Darrick J. Wong
2024-04-30 3:29 ` [PATCH 22/26] xfs: check and repair the verity inode flag state Darrick J. Wong
2024-04-30 3:30 ` [PATCH 23/26] xfs: teach online repair to evaluate fsverity xattrs Darrick J. Wong
2024-04-30 3:30 ` [PATCH 24/26] xfs: report verity failures through the health system Darrick J. Wong
2024-04-30 3:30 ` [PATCH 25/26] xfs: make it possible to disable fsverity Darrick J. Wong
2024-05-01 6:48 ` Christoph Hellwig
2024-05-01 22:50 ` Darrick J. Wong
2024-05-02 0:15 ` Eric Biggers
2024-05-08 20:31 ` Darrick J. Wong
2024-05-09 5:04 ` Christoph Hellwig
2024-05-09 14:45 ` Darrick J. Wong
2024-05-09 15:06 ` Christoph Hellwig
2024-05-09 15:09 ` Darrick J. Wong
2024-05-09 15:13 ` Christoph Hellwig
2024-05-09 15:43 ` Darrick J. Wong
2024-05-17 19:36 ` Theodore Ts'o
2024-04-30 3:30 ` [PATCH 26/26] xfs: enable ro-compat fs-verity flag Darrick J. Wong
2024-04-30 3:19 ` [PATCHSET v5.6] xfsprogs: fs-verity support for XFS Darrick J. Wong
2024-04-30 3:31 ` [PATCH 01/38] fs: add FS_XFLAG_VERITY for verity files Darrick J. Wong
2024-04-30 3:31 ` [PATCH 02/38] xfs: use unsigned ints for non-negative quantities in xfs_attr_remote.c Darrick J. Wong
2024-04-30 3:31 ` [PATCH 03/38] xfs: turn XFS_ATTR3_RMT_BUF_SPACE into a function Darrick J. Wong
2024-04-30 3:31 ` [PATCH 04/38] xfs: create a helper to compute the blockcount of a max sized remote value Darrick J. Wong
2024-04-30 3:32 ` [PATCH 05/38] xfs: minor cleanups of xfs_attr3_rmt_blocks Darrick J. Wong
2024-04-30 3:32 ` [PATCH 06/38] xfs: use an empty transaction to protect xfs_attr_get from deadlocks Darrick J. Wong
2024-04-30 3:32 ` [PATCH 07/38] xfs: add attribute type for fs-verity Darrick J. Wong
2024-04-30 3:32 ` [PATCH 08/38] xfs: do not use xfs_attr3_rmt_hdr for remote verity value blocks Darrick J. Wong
2024-04-30 3:33 ` [PATCH 09/38] xfs: add fs-verity ro-compat flag Darrick J. Wong
2024-04-30 3:33 ` [PATCH 10/38] xfs: add inode on-disk VERITY flag Darrick J. Wong
2024-04-30 3:33 ` [PATCH 11/38] xfs: add fs-verity support Darrick J. Wong
2024-04-30 3:34 ` Darrick J. Wong [this message]
2024-04-30 3:34 ` [PATCH 13/38] xfs: advertise fs-verity being available on filesystem Darrick J. Wong
2024-04-30 3:34 ` [PATCH 14/38] xfs: report verity failures through the health system Darrick J. Wong
2024-04-30 3:34 ` [PATCH 15/38] xfs: enable ro-compat fs-verity flag Darrick J. Wong
2024-04-30 3:35 ` [PATCH 16/38] libfrog: add fsverity to xfs_report_geom output Darrick J. Wong
2024-04-30 3:35 ` [PATCH 17/38] xfs_db: introduce attr_modify command Darrick J. Wong
2024-04-30 3:35 ` [PATCH 18/38] xfs_db: add ATTR_PARENT support to " Darrick J. Wong
2024-04-30 3:35 ` [PATCH 19/38] xfs_db: make attr_set/remove/modify be able to handle fs-verity attrs Darrick J. Wong
2024-04-30 3:36 ` [PATCH 20/38] man: document attr_modify command Darrick J. Wong
2024-04-30 3:36 ` [PATCH 21/38] xfs_db: create hex string as a field type Darrick J. Wong
2024-04-30 3:36 ` [PATCH 22/38] xfs_db: dump verity features and metadata Darrick J. Wong
2024-04-30 3:36 ` [PATCH 23/38] xfs_db: dump merkle tree data Darrick J. Wong
2024-04-30 3:37 ` [PATCH 24/38] xfs_db: dump the verity descriptor Darrick J. Wong
2024-04-30 3:37 ` [PATCH 25/38] xfs_db: don't obfuscate verity xattrs Darrick J. Wong
2024-04-30 3:37 ` [PATCH 26/38] xfs_db: dump the inode verity flag Darrick J. Wong
2024-04-30 3:37 ` [PATCH 27/38] xfs_db: compute hashes of merkle tree blocks Darrick J. Wong
2024-04-30 3:38 ` [PATCH 28/38] xfs_repair: junk fsverity xattrs when unnecessary Darrick J. Wong
2024-04-30 3:38 ` [PATCH 29/38] xfs_repair: clear verity iflag when verity isn't supported Darrick J. Wong
2024-04-30 3:38 ` [PATCH 30/38] xfs_repair: handle verity remote attrs Darrick J. Wong
2024-04-30 3:38 ` [PATCH 31/38] xfs_repair: allow upgrading filesystems with verity Darrick J. Wong
2024-04-30 3:39 ` [PATCH 32/38] xfs_scrub: check verity file metadata Darrick J. Wong
2024-04-30 3:39 ` [PATCH 33/38] xfs_scrub: validate verity file contents when doing a media scan Darrick J. Wong
2024-04-30 3:39 ` [PATCH 34/38] xfs_scrub: use MADV_POPULATE_READ to check verity files Darrick J. Wong
2024-04-30 3:40 ` [PATCH 35/38] xfs_spaceman: report data corruption Darrick J. Wong
2024-04-30 3:40 ` [PATCH 36/38] xfs_io: report fsverity status via statx Darrick J. Wong
2024-04-30 3:40 ` [PATCH 37/38] xfs_io: create magic command to disable verity Darrick J. Wong
2024-04-30 3:40 ` [PATCH 38/38] mkfs.xfs: add verity parameter Darrick J. Wong
2024-04-30 3:19 ` [PATCHSET v5.6] fstests: fs-verity support for XFS Darrick J. Wong
2024-04-30 3:41 ` [PATCH 1/6] common/verity: enable fsverity " Darrick J. Wong
2024-04-30 12:39 ` Andrey Albershteyn
2024-04-30 15:35 ` Darrick J. Wong
2024-04-30 3:41 ` [PATCH 2/6] xfs/{021,122}: adapt to fsverity xattrs Darrick J. Wong
2024-04-30 12:46 ` Andrey Albershteyn
2024-04-30 15:36 ` Darrick J. Wong
2024-04-30 3:41 ` [PATCH 3/6] xfs/122: adapt to fsverity Darrick J. Wong
2024-04-30 12:45 ` Andrey Albershteyn
2024-04-30 15:37 ` Darrick J. Wong
2024-04-30 3:41 ` [PATCH 4/6] xfs: test xfs_scrub detection and correction of corrupt fsverity metadata Darrick J. Wong
2024-04-30 12:29 ` Andrey Albershteyn
2024-04-30 15:43 ` Darrick J. Wong
2024-04-30 3:42 ` [PATCH 5/6] xfs: test disabling fsverity Darrick J. Wong
2024-04-30 12:56 ` Andrey Albershteyn
2024-04-30 13:11 ` Andrey Albershteyn
2024-04-30 15:48 ` Darrick J. Wong
2024-04-30 18:06 ` Andrey Albershteyn
2024-04-30 3:42 ` [PATCH 6/6] common/populate: add verity files to populate xfs images Darrick J. Wong
2024-04-30 13:22 ` Andrey Albershteyn
2024-04-30 15:49 ` Darrick J. Wong
2024-05-11 5:01 ` [PATCHSET v5.6] fstests: fs-verity support for XFS Zorro Lang
2024-05-17 15:56 ` Darrick J. Wong
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