fs/buffer.c: make block-size be per-page and protected by the page lock
This makes the buffer size handling be a per-page thing, which allows us to not have to worry about locking too much when changing the buffer size. If a page doesn't have buffers, we still need to read the block size from the inode, but we can do that with ACCESS_ONCE(), so that even if the size is changing, we get a consistent value. This doesn't convert all functions - many of the buffer functions are used purely by filesystems, which in turn results in the buffer size being fixed at mount-time. So they don't have the same consistency issues that the raw device access can have. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
9489e9dcae
commit
45bce8f3e3
79
fs/buffer.c
79
fs/buffer.c
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@ -1552,6 +1552,28 @@ void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
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}
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}
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EXPORT_SYMBOL(unmap_underlying_metadata);
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EXPORT_SYMBOL(unmap_underlying_metadata);
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/*
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* Size is a power-of-two in the range 512..PAGE_SIZE,
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* and the case we care about most is PAGE_SIZE.
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*
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* So this *could* possibly be written with those
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* constraints in mind (relevant mostly if some
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* architecture has a slow bit-scan instruction)
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*/
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static inline int block_size_bits(unsigned int blocksize)
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{
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return ilog2(blocksize);
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}
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static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
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{
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BUG_ON(!PageLocked(page));
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if (!page_has_buffers(page))
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create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
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return page_buffers(page);
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}
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/*
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/*
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* NOTE! All mapped/uptodate combinations are valid:
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* NOTE! All mapped/uptodate combinations are valid:
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*
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*
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@ -1589,19 +1611,13 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
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sector_t block;
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sector_t block;
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sector_t last_block;
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sector_t last_block;
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struct buffer_head *bh, *head;
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struct buffer_head *bh, *head;
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const unsigned blocksize = 1 << inode->i_blkbits;
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unsigned int blocksize, bbits;
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int nr_underway = 0;
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int nr_underway = 0;
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int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
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int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
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WRITE_SYNC : WRITE);
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WRITE_SYNC : WRITE);
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BUG_ON(!PageLocked(page));
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head = create_page_buffers(page, inode,
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last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
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if (!page_has_buffers(page)) {
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create_empty_buffers(page, blocksize,
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(1 << BH_Dirty)|(1 << BH_Uptodate));
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(1 << BH_Dirty)|(1 << BH_Uptodate));
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}
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/*
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/*
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* Be very careful. We have no exclusion from __set_page_dirty_buffers
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* Be very careful. We have no exclusion from __set_page_dirty_buffers
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@ -1613,9 +1629,12 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
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* handle that here by just cleaning them.
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* handle that here by just cleaning them.
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*/
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*/
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block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
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head = page_buffers(page);
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bh = head;
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bh = head;
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blocksize = bh->b_size;
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bbits = block_size_bits(blocksize);
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block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
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last_block = (i_size_read(inode) - 1) >> bbits;
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/*
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/*
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* Get all the dirty buffers mapped to disk addresses and
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* Get all the dirty buffers mapped to disk addresses and
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@ -1806,12 +1825,10 @@ int __block_write_begin(struct page *page, loff_t pos, unsigned len,
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BUG_ON(to > PAGE_CACHE_SIZE);
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BUG_ON(to > PAGE_CACHE_SIZE);
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BUG_ON(from > to);
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BUG_ON(from > to);
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blocksize = 1 << inode->i_blkbits;
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head = create_page_buffers(page, inode, 0);
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if (!page_has_buffers(page))
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blocksize = head->b_size;
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create_empty_buffers(page, blocksize, 0);
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bbits = block_size_bits(blocksize);
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head = page_buffers(page);
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bbits = inode->i_blkbits;
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block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
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block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
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for(bh = head, block_start = 0; bh != head || !block_start;
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for(bh = head, block_start = 0; bh != head || !block_start;
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@ -1881,11 +1898,11 @@ static int __block_commit_write(struct inode *inode, struct page *page,
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unsigned blocksize;
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unsigned blocksize;
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struct buffer_head *bh, *head;
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struct buffer_head *bh, *head;
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blocksize = 1 << inode->i_blkbits;
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bh = head = page_buffers(page);
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blocksize = bh->b_size;
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for(bh = head = page_buffers(page), block_start = 0;
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block_start = 0;
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bh != head || !block_start;
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do {
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block_start=block_end, bh = bh->b_this_page) {
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block_end = block_start + blocksize;
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block_end = block_start + blocksize;
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if (block_end <= from || block_start >= to) {
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if (block_end <= from || block_start >= to) {
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if (!buffer_uptodate(bh))
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if (!buffer_uptodate(bh))
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@ -1895,7 +1912,10 @@ static int __block_commit_write(struct inode *inode, struct page *page,
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mark_buffer_dirty(bh);
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mark_buffer_dirty(bh);
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}
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}
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clear_buffer_new(bh);
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clear_buffer_new(bh);
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}
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block_start = block_end;
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bh = bh->b_this_page;
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} while (bh != head);
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/*
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/*
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* If this is a partial write which happened to make all buffers
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* If this is a partial write which happened to make all buffers
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@ -2020,7 +2040,6 @@ EXPORT_SYMBOL(generic_write_end);
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int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
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int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
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unsigned long from)
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unsigned long from)
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{
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{
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struct inode *inode = page->mapping->host;
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unsigned block_start, block_end, blocksize;
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unsigned block_start, block_end, blocksize;
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unsigned to;
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unsigned to;
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struct buffer_head *bh, *head;
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struct buffer_head *bh, *head;
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@ -2029,13 +2048,13 @@ int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
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if (!page_has_buffers(page))
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if (!page_has_buffers(page))
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return 0;
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return 0;
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blocksize = 1 << inode->i_blkbits;
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head = page_buffers(page);
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blocksize = head->b_size;
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to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
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to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
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to = from + to;
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to = from + to;
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if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
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if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
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return 0;
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return 0;
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head = page_buffers(page);
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bh = head;
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bh = head;
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block_start = 0;
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block_start = 0;
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do {
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do {
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@ -2068,18 +2087,16 @@ int block_read_full_page(struct page *page, get_block_t *get_block)
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struct inode *inode = page->mapping->host;
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struct inode *inode = page->mapping->host;
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sector_t iblock, lblock;
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sector_t iblock, lblock;
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struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
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struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
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unsigned int blocksize;
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unsigned int blocksize, bbits;
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int nr, i;
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int nr, i;
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int fully_mapped = 1;
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int fully_mapped = 1;
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BUG_ON(!PageLocked(page));
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head = create_page_buffers(page, inode, 0);
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blocksize = 1 << inode->i_blkbits;
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blocksize = head->b_size;
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if (!page_has_buffers(page))
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bbits = block_size_bits(blocksize);
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create_empty_buffers(page, blocksize, 0);
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head = page_buffers(page);
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iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
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iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
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lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
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lblock = (i_size_read(inode)+blocksize-1) >> bbits;
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bh = head;
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bh = head;
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nr = 0;
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nr = 0;
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i = 0;
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i = 0;
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