kmap_atomic() is being deprecated in favor of kmap_local_page() where it
is feasible. With kmap_local_page() mappings are per thread, CPU local,
and not globally visible.
As far as I can see, the kmap_atomic() calls in compression.c and in
inode.c can be safely converted.
Above all else, David Sterba has confirmed that "The context in
check_compressed_csum is atomic [...]" and that "kmap_atomic() in inode.c
[...] also can be replaced by kmap_local_page().".[1]
Therefore, convert all kmap_atomic() calls currently still left in fs/btrfs
to kmap_local_page().
Tested with xfstests on a QEMU + KVM 32-bits VM with 4GB RAM and booting a
kernel with HIGHMEM64GB enabled.
[1] https://lore.kernel.org/linux-btrfs/20220601132545.GM20
[email protected]/
Suggested-by: Ira Weiny <[email protected]>
Suggested-by: David Sterba <[email protected]>
Signed-off-by: Fabio M. De Francesco <[email protected]>
---
Tests of groups "quick" and "compress" output several errors largely due
to memory leaks and shift-out-of-bounds. However, these errors are exactly
the same which are output without this and other conversions of mine to use
kmap_local_page(). Therefore, it looks like these changes don't introduce
regressions.
The previous RFC PATCH can be ignored:
https://lore.kernel.org/lkml/[email protected]/
With this patch, in fs/btrfs there are no longer call sites of kmap() and
kmap_atomic().
fs/btrfs/compression.c | 4 ++--
fs/btrfs/inode.c | 12 ++++++------
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index f4564f32f6d9..b49719ae45b4 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -175,10 +175,10 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
/* Hash through the page sector by sector */
for (pg_offset = 0; pg_offset < bytes_left;
pg_offset += sectorsize) {
- kaddr = kmap_atomic(page);
+ kaddr = kmap_local_page(page);
crypto_shash_digest(shash, kaddr + pg_offset,
sectorsize, csum);
- kunmap_atomic(kaddr);
+ kunmap_local(kaddr);
if (memcmp(&csum, cb_sum, csum_size) != 0) {
btrfs_print_data_csum_error(inode, disk_start,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e921d6c432ac..0a7a621710f6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -332,9 +332,9 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
cur_size = min_t(unsigned long, compressed_size,
PAGE_SIZE);
- kaddr = kmap_atomic(cpage);
+ kaddr = kmap_local_page(cpage);
write_extent_buffer(leaf, kaddr, ptr, cur_size);
- kunmap_atomic(kaddr);
+ kunmap_local(kaddr);
i++;
ptr += cur_size;
@@ -345,9 +345,9 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
} else {
page = find_get_page(inode->vfs_inode.i_mapping, 0);
btrfs_set_file_extent_compression(leaf, ei, 0);
- kaddr = kmap_atomic(page);
+ kaddr = kmap_local_page(page);
write_extent_buffer(leaf, kaddr, ptr, size);
- kunmap_atomic(kaddr);
+ kunmap_local(kaddr);
put_page(page);
}
btrfs_mark_buffer_dirty(leaf);
@@ -3357,11 +3357,11 @@ static int check_data_csum(struct inode *inode, struct btrfs_bio *bbio,
offset_sectors = bio_offset >> fs_info->sectorsize_bits;
csum_expected = ((u8 *)bbio->csum) + offset_sectors * csum_size;
- kaddr = kmap_atomic(page);
+ kaddr = kmap_local_page(page);
shash->tfm = fs_info->csum_shash;
crypto_shash_digest(shash, kaddr + pgoff, len, csum);
- kunmap_atomic(kaddr);
+ kunmap_local(kaddr);
if (memcmp(csum, csum_expected, csum_size))
goto zeroit;
--
2.36.1
On Mon, Jun 27, 2022 at 07:48:49PM +0200, Fabio M. De Francesco wrote:
> kmap_atomic() is being deprecated in favor of kmap_local_page() where it
> is feasible. With kmap_local_page() mappings are per thread, CPU local,
> and not globally visible.
>
> As far as I can see, the kmap_atomic() calls in compression.c and in
> inode.c can be safely converted.
>
> Above all else, David Sterba has confirmed that "The context in
> check_compressed_csum is atomic [...]" and that "kmap_atomic() in inode.c
> [...] also can be replaced by kmap_local_page().".[1]
>
> Therefore, convert all kmap_atomic() calls currently still left in fs/btrfs
> to kmap_local_page().
>
> Tested with xfstests on a QEMU + KVM 32-bits VM with 4GB RAM and booting a
> kernel with HIGHMEM64GB enabled.
>
> [1] https://lore.kernel.org/linux-btrfs/20220601132545.GM20
> [email protected]/
>
> Suggested-by: Ira Weiny <[email protected]>
Test failures aside this looks ok to me.
Reviewed-by: Ira Weiny <[email protected]>
> Suggested-by: David Sterba <[email protected]>
> Signed-off-by: Fabio M. De Francesco <[email protected]>
> ---
>
> Tests of groups "quick" and "compress" output several errors largely due
> to memory leaks and shift-out-of-bounds. However, these errors are exactly
> the same which are output without this and other conversions of mine to use
> kmap_local_page(). Therefore, it looks like these changes don't introduce
> regressions.
>
> The previous RFC PATCH can be ignored:
> https://lore.kernel.org/lkml/[email protected]/
>
> With this patch, in fs/btrfs there are no longer call sites of kmap() and
> kmap_atomic().
>
> fs/btrfs/compression.c | 4 ++--
> fs/btrfs/inode.c | 12 ++++++------
> 2 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index f4564f32f6d9..b49719ae45b4 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -175,10 +175,10 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
> /* Hash through the page sector by sector */
> for (pg_offset = 0; pg_offset < bytes_left;
> pg_offset += sectorsize) {
> - kaddr = kmap_atomic(page);
> + kaddr = kmap_local_page(page);
> crypto_shash_digest(shash, kaddr + pg_offset,
> sectorsize, csum);
> - kunmap_atomic(kaddr);
> + kunmap_local(kaddr);
>
> if (memcmp(&csum, cb_sum, csum_size) != 0) {
> btrfs_print_data_csum_error(inode, disk_start,
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index e921d6c432ac..0a7a621710f6 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -332,9 +332,9 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
> cur_size = min_t(unsigned long, compressed_size,
> PAGE_SIZE);
>
> - kaddr = kmap_atomic(cpage);
> + kaddr = kmap_local_page(cpage);
> write_extent_buffer(leaf, kaddr, ptr, cur_size);
> - kunmap_atomic(kaddr);
> + kunmap_local(kaddr);
>
> i++;
> ptr += cur_size;
> @@ -345,9 +345,9 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
> } else {
> page = find_get_page(inode->vfs_inode.i_mapping, 0);
> btrfs_set_file_extent_compression(leaf, ei, 0);
> - kaddr = kmap_atomic(page);
> + kaddr = kmap_local_page(page);
> write_extent_buffer(leaf, kaddr, ptr, size);
> - kunmap_atomic(kaddr);
> + kunmap_local(kaddr);
> put_page(page);
> }
> btrfs_mark_buffer_dirty(leaf);
> @@ -3357,11 +3357,11 @@ static int check_data_csum(struct inode *inode, struct btrfs_bio *bbio,
> offset_sectors = bio_offset >> fs_info->sectorsize_bits;
> csum_expected = ((u8 *)bbio->csum) + offset_sectors * csum_size;
>
> - kaddr = kmap_atomic(page);
> + kaddr = kmap_local_page(page);
> shash->tfm = fs_info->csum_shash;
>
> crypto_shash_digest(shash, kaddr + pgoff, len, csum);
> - kunmap_atomic(kaddr);
> + kunmap_local(kaddr);
>
> if (memcmp(csum, csum_expected, csum_size))
> goto zeroit;
> --
> 2.36.1
>
On Mon, Jun 27, 2022 at 07:48:49PM +0200, Fabio M. De Francesco wrote:
> kmap_atomic() is being deprecated in favor of kmap_local_page() where it
> is feasible. With kmap_local_page() mappings are per thread, CPU local,
> and not globally visible.
>
> As far as I can see, the kmap_atomic() calls in compression.c and in
> inode.c can be safely converted.
>
> Above all else, David Sterba has confirmed that "The context in
> check_compressed_csum is atomic [...]" and that "kmap_atomic() in inode.c
> [...] also can be replaced by kmap_local_page().".[1]
>
> Therefore, convert all kmap_atomic() calls currently still left in fs/btrfs
> to kmap_local_page().
>
> Tested with xfstests on a QEMU + KVM 32-bits VM with 4GB RAM and booting a
> kernel with HIGHMEM64GB enabled.
>
> [1] https://lore.kernel.org/linux-btrfs/20220601132545.GM20
> [email protected]/
>
> Suggested-by: Ira Weiny <[email protected]>
> Suggested-by: David Sterba <[email protected]>
> Signed-off-by: Fabio M. De Francesco <[email protected]>
Added to the kmap patches, thanks.
> ---
>
> Tests of groups "quick" and "compress" output several errors largely due
> to memory leaks and shift-out-of-bounds. However, these errors are exactly
> the same which are output without this and other conversions of mine to use
> kmap_local_page(). Therefore, it looks like these changes don't introduce
> regressions.
>
> The previous RFC PATCH can be ignored:
> https://lore.kernel.org/lkml/[email protected]/
>
> With this patch, in fs/btrfs there are no longer call sites of kmap() and
> kmap_atomic().
>
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -332,9 +332,9 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
> cur_size = min_t(unsigned long, compressed_size,
> PAGE_SIZE);
>
> - kaddr = kmap_atomic(cpage);
> + kaddr = kmap_local_page(cpage);
After some cleanups and simplifications in checksumming functions (that
mapped the buffers) only kmap_atomic in insert_inline_extent remains, so
the final patch will be a bit shorter.
> write_extent_buffer(leaf, kaddr, ptr, cur_size);
> - kunmap_atomic(kaddr);
> + kunmap_local(kaddr);
>
> i++;
> ptr += cur_size;
> @@ -345,9 +345,9 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
> } else {
> page = find_get_page(inode->vfs_inode.i_mapping, 0);
> btrfs_set_file_extent_compression(leaf, ei, 0);
> - kaddr = kmap_atomic(page);
> + kaddr = kmap_local_page(page);
> write_extent_buffer(leaf, kaddr, ptr, size);
> - kunmap_atomic(kaddr);
> + kunmap_local(kaddr);
> put_page(page);
> }
> btrfs_mark_buffer_dirty(leaf);