mirror of
https://github.com/torvalds/linux.git
synced 2025-10-31 16:48:26 +02:00
btrfs: subpage: make lzo_compress_pages() compatible
There are several problems in lzo_compress_pages() preventing it from being subpage compatible: - No page offset is calculated when reading from inode pages For subpage case, we could have @start which is not aligned to PAGE_SIZE. Thus the destination where we read data from must take offset in page into consideration. - The padding for segment header is bound to PAGE_SIZE This means, for subpage case we can skip several corners where on x86 machines we need to add padding zeros. The rework will: - Update the comment to replace "page" with "sector" - Introduce a new helper, copy_compressed_data_to_page(), to do the copy So that we don't need to bother page switching for both input and output. Now in lzo_compress_pages() we only care about page switching for input, while in copy_compressed_data_to_page() we only care about the page switching for output. - Only one main cursor For lzo_compress_pages() we use @cur_in as main cursor. It will be the file offset we are currently at. All other helper variables will be only declared inside the loop. For copy_compressed_data_to_page() it's similar, we will have @cur_out at the main cursor, which records how many bytes are in the output. Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo
David Sterba
parent
2b83a0eea5
commit
d4088803f5
1 changed files with 132 additions and 134 deletions
266
fs/btrfs/lzo.c
266
fs/btrfs/lzo.c
|
|
@ -32,19 +32,19 @@
|
|||
* payload.
|
||||
* One regular LZO compressed extent can have one or more segments.
|
||||
* For inlined LZO compressed extent, only one segment is allowed.
|
||||
* One segment represents at most one page of uncompressed data.
|
||||
* One segment represents at most one sector of uncompressed data.
|
||||
*
|
||||
* 2.1 Segment header
|
||||
* Fixed size. LZO_LEN (4) bytes long, LE32.
|
||||
* Records the total size of the segment (not including the header).
|
||||
* Segment header never crosses page boundary, thus it's possible to
|
||||
* have at most 3 padding zeros at the end of the page.
|
||||
* Segment header never crosses sector boundary, thus it's possible to
|
||||
* have at most 3 padding zeros at the end of the sector.
|
||||
*
|
||||
* 2.2 Data Payload
|
||||
* Variable size. Size up limit should be lzo1x_worst_compress(PAGE_SIZE)
|
||||
* which is 4419 for a 4KiB page.
|
||||
* Variable size. Size up limit should be lzo1x_worst_compress(sectorsize)
|
||||
* which is 4419 for a 4KiB sectorsize.
|
||||
*
|
||||
* Example:
|
||||
* Example with 4K sectorsize:
|
||||
* Page 1:
|
||||
* 0 0x2 0x4 0x6 0x8 0xa 0xc 0xe 0x10
|
||||
* 0x0000 | Header | SegHdr 01 | Data payload 01 ... |
|
||||
|
|
@ -112,163 +112,161 @@ static inline size_t read_compress_length(const char *buf)
|
|||
return le32_to_cpu(dlen);
|
||||
}
|
||||
|
||||
/*
|
||||
* Will do:
|
||||
*
|
||||
* - Write a segment header into the destination
|
||||
* - Copy the compressed buffer into the destination
|
||||
* - Make sure we have enough space in the last sector to fit a segment header
|
||||
* If not, we will pad at most (LZO_LEN (4)) - 1 bytes of zeros.
|
||||
*
|
||||
* Will allocate new pages when needed.
|
||||
*/
|
||||
static int copy_compressed_data_to_page(char *compressed_data,
|
||||
size_t compressed_size,
|
||||
struct page **out_pages,
|
||||
u32 *cur_out,
|
||||
const u32 sectorsize)
|
||||
{
|
||||
u32 sector_bytes_left;
|
||||
u32 orig_out;
|
||||
struct page *cur_page;
|
||||
|
||||
/*
|
||||
* We never allow a segment header crossing sector boundary, previous
|
||||
* run should ensure we have enough space left inside the sector.
|
||||
*/
|
||||
ASSERT((*cur_out / sectorsize) == (*cur_out + LZO_LEN - 1) / sectorsize);
|
||||
|
||||
cur_page = out_pages[*cur_out / PAGE_SIZE];
|
||||
/* Allocate a new page */
|
||||
if (!cur_page) {
|
||||
cur_page = alloc_page(GFP_NOFS);
|
||||
if (!cur_page)
|
||||
return -ENOMEM;
|
||||
out_pages[*cur_out / PAGE_SIZE] = cur_page;
|
||||
}
|
||||
|
||||
write_compress_length(page_address(cur_page) + offset_in_page(*cur_out),
|
||||
compressed_size);
|
||||
*cur_out += LZO_LEN;
|
||||
|
||||
orig_out = *cur_out;
|
||||
|
||||
/* Copy compressed data */
|
||||
while (*cur_out - orig_out < compressed_size) {
|
||||
u32 copy_len = min_t(u32, sectorsize - *cur_out % sectorsize,
|
||||
orig_out + compressed_size - *cur_out);
|
||||
|
||||
cur_page = out_pages[*cur_out / PAGE_SIZE];
|
||||
/* Allocate a new page */
|
||||
if (!cur_page) {
|
||||
cur_page = alloc_page(GFP_NOFS);
|
||||
if (!cur_page)
|
||||
return -ENOMEM;
|
||||
out_pages[*cur_out / PAGE_SIZE] = cur_page;
|
||||
}
|
||||
|
||||
memcpy(page_address(cur_page) + offset_in_page(*cur_out),
|
||||
compressed_data + *cur_out - orig_out, copy_len);
|
||||
|
||||
*cur_out += copy_len;
|
||||
}
|
||||
|
||||
/*
|
||||
* Check if we can fit the next segment header into the remaining space
|
||||
* of the sector.
|
||||
*/
|
||||
sector_bytes_left = round_up(*cur_out, sectorsize) - *cur_out;
|
||||
if (sector_bytes_left >= LZO_LEN || sector_bytes_left == 0)
|
||||
return 0;
|
||||
|
||||
/* The remaining size is not enough, pad it with zeros */
|
||||
memset(page_address(cur_page) + offset_in_page(*cur_out), 0,
|
||||
sector_bytes_left);
|
||||
*cur_out += sector_bytes_left;
|
||||
return 0;
|
||||
}
|
||||
|
||||
int lzo_compress_pages(struct list_head *ws, struct address_space *mapping,
|
||||
u64 start, struct page **pages, unsigned long *out_pages,
|
||||
unsigned long *total_in, unsigned long *total_out)
|
||||
{
|
||||
struct workspace *workspace = list_entry(ws, struct workspace, list);
|
||||
const u32 sectorsize = btrfs_sb(mapping->host->i_sb)->sectorsize;
|
||||
struct page *page_in = NULL;
|
||||
int ret = 0;
|
||||
char *data_in;
|
||||
char *cpage_out, *sizes_ptr;
|
||||
int nr_pages = 0;
|
||||
struct page *in_page = NULL;
|
||||
struct page *out_page = NULL;
|
||||
unsigned long bytes_left;
|
||||
unsigned long len = *total_out;
|
||||
unsigned long nr_dest_pages = *out_pages;
|
||||
const unsigned long max_out = nr_dest_pages * PAGE_SIZE;
|
||||
size_t in_len;
|
||||
size_t out_len;
|
||||
char *buf;
|
||||
unsigned long tot_in = 0;
|
||||
unsigned long tot_out = 0;
|
||||
unsigned long pg_bytes_left;
|
||||
unsigned long out_offset;
|
||||
unsigned long bytes;
|
||||
/* Points to the file offset of input data */
|
||||
u64 cur_in = start;
|
||||
/* Points to the current output byte */
|
||||
u32 cur_out = 0;
|
||||
u32 len = *total_out;
|
||||
|
||||
*out_pages = 0;
|
||||
*total_out = 0;
|
||||
*total_in = 0;
|
||||
|
||||
in_page = find_get_page(mapping, start >> PAGE_SHIFT);
|
||||
data_in = page_address(in_page);
|
||||
|
||||
/*
|
||||
* store the size of all chunks of compressed data in
|
||||
* the first 4 bytes
|
||||
* Skip the header for now, we will later come back and write the total
|
||||
* compressed size
|
||||
*/
|
||||
out_page = alloc_page(GFP_NOFS);
|
||||
if (out_page == NULL) {
|
||||
ret = -ENOMEM;
|
||||
goto out;
|
||||
}
|
||||
cpage_out = page_address(out_page);
|
||||
out_offset = LZO_LEN;
|
||||
tot_out = LZO_LEN;
|
||||
pages[0] = out_page;
|
||||
nr_pages = 1;
|
||||
pg_bytes_left = PAGE_SIZE - LZO_LEN;
|
||||
cur_out += LZO_LEN;
|
||||
while (cur_in < start + len) {
|
||||
const u32 sectorsize_mask = sectorsize - 1;
|
||||
u32 sector_off = (cur_in - start) & sectorsize_mask;
|
||||
u32 in_len;
|
||||
size_t out_len;
|
||||
|
||||
/* compress at most one page of data each time */
|
||||
in_len = min(len, PAGE_SIZE);
|
||||
while (tot_in < len) {
|
||||
ret = lzo1x_1_compress(data_in, in_len, workspace->cbuf,
|
||||
&out_len, workspace->mem);
|
||||
if (ret != LZO_E_OK) {
|
||||
pr_debug("BTRFS: lzo in loop returned %d\n",
|
||||
ret);
|
||||
/* Get the input page first */
|
||||
if (!page_in) {
|
||||
page_in = find_get_page(mapping, cur_in >> PAGE_SHIFT);
|
||||
ASSERT(page_in);
|
||||
}
|
||||
|
||||
/* Compress at most one sector of data each time */
|
||||
in_len = min_t(u32, start + len - cur_in, sectorsize - sector_off);
|
||||
ASSERT(in_len);
|
||||
ret = lzo1x_1_compress(page_address(page_in) +
|
||||
offset_in_page(cur_in), in_len,
|
||||
workspace->cbuf, &out_len,
|
||||
workspace->mem);
|
||||
if (ret < 0) {
|
||||
pr_debug("BTRFS: lzo in loop returned %d\n", ret);
|
||||
ret = -EIO;
|
||||
goto out;
|
||||
}
|
||||
|
||||
/* store the size of this chunk of compressed data */
|
||||
write_compress_length(cpage_out + out_offset, out_len);
|
||||
tot_out += LZO_LEN;
|
||||
out_offset += LZO_LEN;
|
||||
pg_bytes_left -= LZO_LEN;
|
||||
ret = copy_compressed_data_to_page(workspace->cbuf, out_len,
|
||||
pages, &cur_out, sectorsize);
|
||||
if (ret < 0)
|
||||
goto out;
|
||||
|
||||
tot_in += in_len;
|
||||
tot_out += out_len;
|
||||
cur_in += in_len;
|
||||
|
||||
/* copy bytes from the working buffer into the pages */
|
||||
buf = workspace->cbuf;
|
||||
while (out_len) {
|
||||
bytes = min_t(unsigned long, pg_bytes_left, out_len);
|
||||
|
||||
memcpy(cpage_out + out_offset, buf, bytes);
|
||||
|
||||
out_len -= bytes;
|
||||
pg_bytes_left -= bytes;
|
||||
buf += bytes;
|
||||
out_offset += bytes;
|
||||
|
||||
/*
|
||||
* we need another page for writing out.
|
||||
*
|
||||
* Note if there's less than 4 bytes left, we just
|
||||
* skip to a new page.
|
||||
*/
|
||||
if ((out_len == 0 && pg_bytes_left < LZO_LEN) ||
|
||||
pg_bytes_left == 0) {
|
||||
if (pg_bytes_left) {
|
||||
memset(cpage_out + out_offset, 0,
|
||||
pg_bytes_left);
|
||||
tot_out += pg_bytes_left;
|
||||
}
|
||||
|
||||
/* we're done, don't allocate new page */
|
||||
if (out_len == 0 && tot_in >= len)
|
||||
break;
|
||||
|
||||
if (nr_pages == nr_dest_pages) {
|
||||
out_page = NULL;
|
||||
ret = -E2BIG;
|
||||
goto out;
|
||||
}
|
||||
|
||||
out_page = alloc_page(GFP_NOFS);
|
||||
if (out_page == NULL) {
|
||||
ret = -ENOMEM;
|
||||
goto out;
|
||||
}
|
||||
cpage_out = page_address(out_page);
|
||||
pages[nr_pages++] = out_page;
|
||||
|
||||
pg_bytes_left = PAGE_SIZE;
|
||||
out_offset = 0;
|
||||
}
|
||||
}
|
||||
|
||||
/* we're making it bigger, give up */
|
||||
if (tot_in > 8192 && tot_in < tot_out) {
|
||||
/*
|
||||
* Check if we're making it bigger after two sectors. And if
|
||||
* it is so, give up.
|
||||
*/
|
||||
if (cur_in - start > sectorsize * 2 && cur_in - start < cur_out) {
|
||||
ret = -E2BIG;
|
||||
goto out;
|
||||
}
|
||||
|
||||
/* we're all done */
|
||||
if (tot_in >= len)
|
||||
break;
|
||||
|
||||
if (tot_out > max_out)
|
||||
break;
|
||||
|
||||
bytes_left = len - tot_in;
|
||||
put_page(in_page);
|
||||
|
||||
start += PAGE_SIZE;
|
||||
in_page = find_get_page(mapping, start >> PAGE_SHIFT);
|
||||
data_in = page_address(in_page);
|
||||
in_len = min(bytes_left, PAGE_SIZE);
|
||||
/* Check if we have reached page boundary */
|
||||
if (IS_ALIGNED(cur_in, PAGE_SIZE)) {
|
||||
put_page(page_in);
|
||||
page_in = NULL;
|
||||
}
|
||||
}
|
||||
|
||||
if (tot_out >= tot_in) {
|
||||
ret = -E2BIG;
|
||||
goto out;
|
||||
}
|
||||
|
||||
/* store the size of all chunks of compressed data */
|
||||
sizes_ptr = page_address(pages[0]);
|
||||
write_compress_length(sizes_ptr, tot_out);
|
||||
/* Store the size of all chunks of compressed data */
|
||||
write_compress_length(page_address(pages[0]), cur_out);
|
||||
|
||||
ret = 0;
|
||||
*total_out = tot_out;
|
||||
*total_in = tot_in;
|
||||
*total_out = cur_out;
|
||||
*total_in = cur_in - start;
|
||||
out:
|
||||
*out_pages = nr_pages;
|
||||
|
||||
if (in_page)
|
||||
put_page(in_page);
|
||||
|
||||
*out_pages = DIV_ROUND_UP(cur_out, PAGE_SIZE);
|
||||
return ret;
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in a new issue