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Revert "btrfs: compression: drop kmap/kunmap from zstd"
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This reverts commit bbaf971.

The kmaps in compression code are still needed and cause crashes on
32bit machines (ARM, x86). Reproducible eg. by running fstest btrfs/004
with enabled LZO or ZSTD compression.

Example stacktrace with ZSTD on a 32bit ARM machine:

  Unable to handle kernel NULL pointer dereference at virtual address 00000000
  pgd = c4159ed3
  [00000000] *pgd=00000000
  Internal error: Oops: 5 [#1] PREEMPT SMP ARM
  Modules linked in:
  CPU: 0 PID: 210 Comm: kworker/u2:3 Not tainted 5.14.0-rc79+ torvalds#12
  Hardware name: Allwinner sun4i/sun5i Families
  Workqueue: btrfs-delalloc btrfs_work_helper
  PC is at mmiocpy+0x48/0x330
  LR is at ZSTD_compressStream_generic+0x15c/0x28c

  (mmiocpy) from [<c0629648>] (ZSTD_compressStream_generic+0x15c/0x28c)
  (ZSTD_compressStream_generic) from [<c06297dc>] (ZSTD_compressStream+0x64/0xa0)
  (ZSTD_compressStream) from [<c049444c>] (zstd_compress_pages+0x170/0x488)
  (zstd_compress_pages) from [<c0496798>] (btrfs_compress_pages+0x124/0x12c)
  (btrfs_compress_pages) from [<c043c068>] (compress_file_range+0x3c0/0x834)
  (compress_file_range) from [<c043c4ec>] (async_cow_start+0x10/0x28)
  (async_cow_start) from [<c0475c3c>] (btrfs_work_helper+0x100/0x230)
  (btrfs_work_helper) from [<c014ef68>] (process_one_work+0x1b4/0x418)
  (process_one_work) from [<c014f210>] (worker_thread+0x44/0x524)
  (worker_thread) from [<c0156aa4>] (kthread+0x180/0x1b0)
  (kthread) from [<c0100150>]

Link: https://lore.kernel.org/all/CAJCQCtT+OuemovPO7GZk8Y8=qtOObr0XTDp8jh4OHD6y84AFxw@mail.gmail.com/
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=214839
Signed-off-by: David Sterba <[email protected]>
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@kdave
kdave committed Oct 29, 2021
1 parent 3a60f65 commit 56ee254
Showing 1 changed file with 18 additions and 9 deletions.
27 changes: 18 additions & 9 deletions fs/btrfs/zstd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -399,7 +399,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,

/* map in the first page of input data */
in_page = find_get_page(mapping, start >> PAGE_SHIFT);
workspace->in_buf.src = page_address(in_page);
workspace->in_buf.src = kmap(in_page);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);

Expand All @@ -411,7 +411,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
goto out;
}
pages[nr_pages++] = out_page;
workspace->out_buf.dst = page_address(out_page);
workspace->out_buf.dst = kmap(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);

Expand Down Expand Up @@ -446,6 +446,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
if (workspace->out_buf.pos == workspace->out_buf.size) {
tot_out += PAGE_SIZE;
max_out -= PAGE_SIZE;
kunmap(out_page);
if (nr_pages == nr_dest_pages) {
out_page = NULL;
ret = -E2BIG;
Expand All @@ -457,7 +458,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
goto out;
}
pages[nr_pages++] = out_page;
workspace->out_buf.dst = page_address(out_page);
workspace->out_buf.dst = kmap(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out,
PAGE_SIZE);
Expand All @@ -472,12 +473,13 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
/* Check if we need more input */
if (workspace->in_buf.pos == workspace->in_buf.size) {
tot_in += PAGE_SIZE;
kunmap(in_page);
put_page(in_page);

start += PAGE_SIZE;
len -= PAGE_SIZE;
in_page = find_get_page(mapping, start >> PAGE_SHIFT);
workspace->in_buf.src = page_address(in_page);
workspace->in_buf.src = kmap(in_page);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
}
Expand All @@ -504,6 +506,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,

tot_out += PAGE_SIZE;
max_out -= PAGE_SIZE;
kunmap(out_page);
if (nr_pages == nr_dest_pages) {
out_page = NULL;
ret = -E2BIG;
Expand All @@ -515,7 +518,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
goto out;
}
pages[nr_pages++] = out_page;
workspace->out_buf.dst = page_address(out_page);
workspace->out_buf.dst = kmap(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
}
Expand All @@ -531,8 +534,12 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
out:
*out_pages = nr_pages;
/* Cleanup */
if (in_page)
if (in_page) {
kunmap(in_page);
put_page(in_page);
}
if (out_page)
kunmap(out_page);
return ret;
}

Expand All @@ -556,7 +563,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
goto done;
}

workspace->in_buf.src = page_address(pages_in[page_in_index]);
workspace->in_buf.src = kmap(pages_in[page_in_index]);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);

Expand Down Expand Up @@ -592,21 +599,23 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
break;

if (workspace->in_buf.pos == workspace->in_buf.size) {
page_in_index++;
kunmap(pages_in[page_in_index++]);
if (page_in_index >= total_pages_in) {
workspace->in_buf.src = NULL;
ret = -EIO;
goto done;
}
srclen -= PAGE_SIZE;
workspace->in_buf.src = page_address(pages_in[page_in_index]);
workspace->in_buf.src = kmap(pages_in[page_in_index]);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
}
}
ret = 0;
zero_fill_bio(cb->orig_bio);
done:
if (workspace->in_buf.src)
kunmap(pages_in[page_in_index]);
return ret;
}

Expand Down

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