42aba3795c
- Fix extent not found when initramfs contains shared extents (bsc#1190982) * 0001-fs-btrfs-Make-extent-item-iteration-to-handle-gaps.patch OBS-URL: https://build.opensuse.org/request/show/935870 OBS-URL: https://build.opensuse.org/package/show/Base:System/grub2?expand=0&rev=398
125 lines
4.4 KiB
Diff
125 lines
4.4 KiB
Diff
From 149df8b7bb86401693e1f064859de0a8906d97b7 Mon Sep 17 00:00:00 2001
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From: Qu Wenruo <wqu@suse.com>
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Date: Thu, 28 Oct 2021 17:44:57 +0800
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Subject: [PATCH] fs/btrfs: Make extent item iteration to handle gaps
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[BUG]
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Grub btrfs implementation can't handle two very basic btrfs file
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layouts:
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1. Mixed inline/regualr extents
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# mkfs.btrfs -f test.img
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# mount test.img /mnt/btrfs
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# xfs_io -f -c "pwrite 0 1k" -c "sync" -c "falloc 0 4k" \
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-c "pwrite 4k 4k" /mnt/btrfs/file
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# umount /mnt/btrfs
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# ./grub-fstest ./grub-fstest --debug=btrfs ~/test.img hex "/file"
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Such mixed inline/regular extents case is not recommended layout,
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but all existing tools and kernel can handle it without problem
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2. NO_HOLES feature
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# mkfs.btrfs -f test.img -O no_holes
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# mount test.img /mnt/btrfs
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# xfs_io -f -c "pwrite 0 4k" -c "pwrite 8k 4k" /mnt/btrfs/file
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# umount /mnt/btrfs
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# ./grub-fstest ./grub-fstest --debug=btrfs ~/test.img hex "/file"
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NO_HOLES feature is going to be the default mkfs feature in the incoming
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v5.15 release, and kernel has support for it since v4.0.
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[CAUSE]
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The way GRUB btrfs code iterates through file extents relies on no gap
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between extents.
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If any gap is hit, then grub btrfs will error out, without any proper
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reason to help debug the bug.
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This is a bad assumption, since a long long time ago btrfs has a new
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feature called NO_HOLES to allow btrfs to skip the padding hole extent
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to reduce metadata usage.
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The NO_HOLES feature is already stable since kernel v4.0 and is going to
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be the default mkfs feature in the incoming v5.15 btrfs-progs release.
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[FIX]
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When there is a extent gap, instead of error out, just try next item.
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This is still not ideal, as kernel/progs/U-boot all do the iteration
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item by item, not relying on the file offset continuity.
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But it will be way more time consuming to correct the whole behavior
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than starting from scratch to build a proper designed btrfs module for GRUB.
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Signed-off-by: Qu Wenruo <wqu@suse.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/fs/btrfs.c | 35 ++++++++++++++++++++++++++++++++---
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1 file changed, 32 insertions(+), 3 deletions(-)
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diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
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index 9625bdf16..b8625197b 100644
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--- a/grub-core/fs/btrfs.c
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+++ b/grub-core/fs/btrfs.c
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@@ -1506,6 +1506,7 @@ grub_btrfs_extent_read (struct grub_btrfs_data *data,
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grub_size_t csize;
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grub_err_t err;
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grub_off_t extoff;
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+ struct grub_btrfs_leaf_descriptor desc;
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if (!data->extent || data->extstart > pos || data->extino != ino
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|| data->exttree != tree || data->extend <= pos)
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{
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@@ -1518,7 +1519,7 @@ grub_btrfs_extent_read (struct grub_btrfs_data *data,
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key_in.type = GRUB_BTRFS_ITEM_TYPE_EXTENT_ITEM;
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key_in.offset = grub_cpu_to_le64 (pos);
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err = lower_bound (data, &key_in, &key_out, tree,
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- &elemaddr, &elemsize, NULL, 0);
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+ &elemaddr, &elemsize, &desc, 0);
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if (err)
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return -1;
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if (key_out.object_id != ino
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@@ -1557,10 +1558,38 @@ grub_btrfs_extent_read (struct grub_btrfs_data *data,
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PRIxGRUB_UINT64_T "\n",
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grub_le_to_cpu64 (key_out.offset),
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grub_le_to_cpu64 (data->extent->size));
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+ /*
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+ * The way of extent item iteration is pretty bad, it completely
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+ * requires all extents are contiguous, which is not ensured.
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+ *
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+ * Features like NO_HOLE and mixed inline/regular extents can cause
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+ * gaps between file extent items.
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+ *
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+ * The correct way is to follow kernel/U-boot to iterate item by
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+ * item, without any assumption on the file offset continuity.
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+ *
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+ * Here we just manually skip to next item and re-do the verification.
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+ *
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+ * TODO: Rework the whole extent item iteration code, if not the
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+ * whole btrfs implementation.
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+ */
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if (data->extend <= pos)
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{
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- grub_error (GRUB_ERR_BAD_FS, "extent not found");
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- return -1;
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+ err = next(data, &desc, &elemaddr, &elemsize, &key_out);
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+ if (err < 0)
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+ return -1;
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+ /* No next item for the inode, we hit the end */
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+ if (err == 0 || key_out.object_id != ino ||
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+ key_out.type != GRUB_BTRFS_ITEM_TYPE_EXTENT_ITEM)
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+ return pos - pos0;
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+
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+ csize = grub_le_to_cpu64(key_out.offset) - pos;
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+ if (csize > len)
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+ csize = len;
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+ buf += csize;
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+ pos += csize;
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+ len -= csize;
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+ continue;
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}
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}
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csize = data->extend - pos;
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--
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2.31.1
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