The use of kmap() is being deprecated in favor of kmap_local_page(). With kmap_local_page(), the mapping is per thread, CPU local and not globally visible. Therefore, use kmap_local_page() / kunmap_local() in zstd.c because in this file the mappings are per thread and are not visible in other contexts; meanwhile refactor zstd_compress_pages() to comply with nested local mapping / unmapping ordering rules. Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM and HIGHMEM64G enabled. These changes passed all tests of the "compress" group. Cc: Filipe Manana <fdmanana@xxxxxxxxxx> Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx> --- v3->v4: Cc Maintainers and lists that had been overlooked when v3 was sent (mostly regarding patch 1/2). v2->v3: Remove unnecessary casts to arguments of kunmap_local() now that this API can take pointers to const void. v1->v2: No changes. Thanks to Ira Weiny for his invaluable help and persevering support. Thanks also to Filipe Manana for identifying a fundamental detail I had overlooked in RFC: https://lore.kernel.org/lkml/20220611093411.GA3779054@falcondesktop/ fs/btrfs/zstd.c | 42 +++++++++++++++++++++++------------------- 1 file changed, 23 insertions(+), 19 deletions(-) diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c index 0fe31a6f6e68..5d2ab0bac9d2 100644 --- a/fs/btrfs/zstd.c +++ b/fs/btrfs/zstd.c @@ -391,6 +391,8 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, *out_pages = 0; *total_out = 0; *total_in = 0; + workspace->in_buf.src = NULL; + workspace->out_buf.dst = NULL; /* Initialize the stream */ stream = zstd_init_cstream(¶ms, len, workspace->mem, @@ -403,7 +405,7 @@ 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 = kmap(in_page); + workspace->in_buf.src = kmap_local_page(in_page); workspace->in_buf.pos = 0; workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE); @@ -415,7 +417,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, goto out; } pages[nr_pages++] = out_page; - workspace->out_buf.dst = kmap(out_page); + workspace->out_buf.dst = kmap_local_page(out_page); workspace->out_buf.pos = 0; workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE); @@ -450,9 +452,9 @@ 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); + kunmap_local(workspace->out_buf.dst); if (nr_pages == nr_dest_pages) { - out_page = NULL; + workspace->out_buf.dst = NULL; ret = -E2BIG; goto out; } @@ -462,7 +464,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, goto out; } pages[nr_pages++] = out_page; - workspace->out_buf.dst = kmap(out_page); + workspace->out_buf.dst = kmap_local_page(out_page); workspace->out_buf.pos = 0; workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE); @@ -477,15 +479,16 @@ 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); + kunmap_local(workspace->out_buf.dst); + kunmap_local(workspace->in_buf.src); put_page(in_page); - start += PAGE_SIZE; len -= PAGE_SIZE; in_page = find_get_page(mapping, start >> PAGE_SHIFT); - workspace->in_buf.src = kmap(in_page); + workspace->in_buf.src = kmap_local_page(in_page); workspace->in_buf.pos = 0; workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE); + workspace->out_buf.dst = kmap_local_page(out_page); } } while (1) { @@ -510,9 +513,9 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, tot_out += PAGE_SIZE; max_out -= PAGE_SIZE; - kunmap(out_page); + kunmap_local(workspace->out_buf.dst); if (nr_pages == nr_dest_pages) { - out_page = NULL; + workspace->out_buf.dst = NULL; ret = -E2BIG; goto out; } @@ -522,7 +525,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, goto out; } pages[nr_pages++] = out_page; - workspace->out_buf.dst = kmap(out_page); + workspace->out_buf.dst = kmap_local_page(out_page); workspace->out_buf.pos = 0; workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE); } @@ -538,12 +541,12 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, out: *out_pages = nr_pages; /* Cleanup */ - if (in_page) { - kunmap(in_page); + if (workspace->out_buf.dst) + kunmap_local(workspace->out_buf.dst); + if (workspace->in_buf.src) { + kunmap_local(workspace->in_buf.src); put_page(in_page); } - if (out_page) - kunmap(out_page); return ret; } @@ -567,7 +570,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb) goto done; } - workspace->in_buf.src = kmap(pages_in[page_in_index]); + workspace->in_buf.src = kmap_local_page(pages_in[page_in_index]); workspace->in_buf.pos = 0; workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE); @@ -603,14 +606,15 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb) break; if (workspace->in_buf.pos == workspace->in_buf.size) { - kunmap(pages_in[page_in_index++]); + kunmap_local(workspace->in_buf.src); + 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 = kmap(pages_in[page_in_index]); + workspace->in_buf.src = kmap_local_page(pages_in[page_in_index]); workspace->in_buf.pos = 0; workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE); } @@ -619,7 +623,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb) zero_fill_bio(cb->orig_bio); done: if (workspace->in_buf.src) - kunmap(pages_in[page_in_index]); + kunmap_local(workspace->in_buf.src); return ret; } -- 2.36.1
