ext4: Switch to iomap for SEEK_HOLE / SEEK_DATA
Switch to the iomap_seek_hole and iomap_seek_data helpers for implementing lseek SEEK_HOLE / SEEK_DATA, and remove all the code that isn't needed any more. Note that with this patch ext4 will now always depend on the iomap code instead of only when CONFIG_DAX is enabled, and it requires adding a call into the extent status tree for iomap_begin as well to properly deal with delalloc extents. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz> [More fixes and cleanups by Andreas]
This commit is contained in:
Christoph Hellwig
committed by
Theodore Ts'o
Theodore Ts'o
parent
7046ae3532
commit
545052e9e3
263
fs/ext4/file.c
263
fs/ext4/file.c
@@ -20,6 +20,7 @@
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/iomap.h>
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#include <linux/mount.h>
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#include <linux/path.h>
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#include <linux/dax.h>
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@@ -437,248 +438,6 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
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return dquot_file_open(inode, filp);
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}
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/*
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* Here we use ext4_map_blocks() to get a block mapping for a extent-based
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* file rather than ext4_ext_walk_space() because we can introduce
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* SEEK_DATA/SEEK_HOLE for block-mapped and extent-mapped file at the same
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* function. When extent status tree has been fully implemented, it will
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* track all extent status for a file and we can directly use it to
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* retrieve the offset for SEEK_DATA/SEEK_HOLE.
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*/
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/*
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* When we retrieve the offset for SEEK_DATA/SEEK_HOLE, we would need to
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* lookup page cache to check whether or not there has some data between
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* [startoff, endoff] because, if this range contains an unwritten extent,
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* we determine this extent as a data or a hole according to whether the
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* page cache has data or not.
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*/
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static int ext4_find_unwritten_pgoff(struct inode *inode,
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int whence,
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ext4_lblk_t end_blk,
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loff_t *offset)
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{
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struct pagevec pvec;
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unsigned int blkbits;
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pgoff_t index;
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pgoff_t end;
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loff_t endoff;
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loff_t startoff;
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loff_t lastoff;
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int found = 0;
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blkbits = inode->i_sb->s_blocksize_bits;
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startoff = *offset;
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lastoff = startoff;
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endoff = (loff_t)end_blk << blkbits;
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index = startoff >> PAGE_SHIFT;
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end = (endoff - 1) >> PAGE_SHIFT;
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pagevec_init(&pvec, 0);
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do {
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int i;
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unsigned long nr_pages;
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nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping,
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&index, end);
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if (nr_pages == 0)
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break;
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for (i = 0; i < nr_pages; i++) {
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struct page *page = pvec.pages[i];
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struct buffer_head *bh, *head;
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/*
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* If current offset is smaller than the page offset,
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* there is a hole at this offset.
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*/
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if (whence == SEEK_HOLE && lastoff < endoff &&
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lastoff < page_offset(pvec.pages[i])) {
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found = 1;
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*offset = lastoff;
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goto out;
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}
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lock_page(page);
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if (unlikely(page->mapping != inode->i_mapping)) {
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unlock_page(page);
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continue;
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}
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if (!page_has_buffers(page)) {
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unlock_page(page);
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continue;
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}
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if (page_has_buffers(page)) {
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lastoff = page_offset(page);
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bh = head = page_buffers(page);
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do {
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if (lastoff + bh->b_size <= startoff)
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goto next;
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if (buffer_uptodate(bh) ||
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buffer_unwritten(bh)) {
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if (whence == SEEK_DATA)
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found = 1;
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} else {
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if (whence == SEEK_HOLE)
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found = 1;
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}
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if (found) {
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*offset = max_t(loff_t,
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startoff, lastoff);
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unlock_page(page);
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goto out;
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}
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next:
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lastoff += bh->b_size;
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bh = bh->b_this_page;
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} while (bh != head);
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}
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lastoff = page_offset(page) + PAGE_SIZE;
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unlock_page(page);
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}
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pagevec_release(&pvec);
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} while (index <= end);
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/* There are no pages upto endoff - that would be a hole in there. */
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if (whence == SEEK_HOLE && lastoff < endoff) {
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found = 1;
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*offset = lastoff;
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}
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out:
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pagevec_release(&pvec);
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return found;
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}
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/*
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* ext4_seek_data() retrieves the offset for SEEK_DATA.
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*/
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static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
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{
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struct inode *inode = file->f_mapping->host;
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struct extent_status es;
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ext4_lblk_t start, last, end;
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loff_t dataoff, isize;
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int blkbits;
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int ret;
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inode_lock(inode);
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isize = i_size_read(inode);
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if (offset < 0 || offset >= isize) {
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inode_unlock(inode);
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return -ENXIO;
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}
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blkbits = inode->i_sb->s_blocksize_bits;
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start = offset >> blkbits;
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last = start;
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end = isize >> blkbits;
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dataoff = offset;
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do {
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ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
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if (ret <= 0) {
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/* No extent found -> no data */
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if (ret == 0)
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ret = -ENXIO;
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inode_unlock(inode);
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return ret;
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}
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last = es.es_lblk;
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if (last != start)
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dataoff = (loff_t)last << blkbits;
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if (!ext4_es_is_unwritten(&es))
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break;
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/*
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* If there is a unwritten extent at this offset,
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* it will be as a data or a hole according to page
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* cache that has data or not.
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*/
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if (ext4_find_unwritten_pgoff(inode, SEEK_DATA,
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es.es_lblk + es.es_len, &dataoff))
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break;
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last += es.es_len;
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dataoff = (loff_t)last << blkbits;
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cond_resched();
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} while (last <= end);
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inode_unlock(inode);
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if (dataoff > isize)
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return -ENXIO;
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return vfs_setpos(file, dataoff, maxsize);
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}
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/*
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* ext4_seek_hole() retrieves the offset for SEEK_HOLE.
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*/
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static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
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{
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struct inode *inode = file->f_mapping->host;
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struct extent_status es;
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ext4_lblk_t start, last, end;
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loff_t holeoff, isize;
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int blkbits;
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int ret;
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inode_lock(inode);
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isize = i_size_read(inode);
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if (offset < 0 || offset >= isize) {
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inode_unlock(inode);
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return -ENXIO;
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}
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blkbits = inode->i_sb->s_blocksize_bits;
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start = offset >> blkbits;
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last = start;
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end = isize >> blkbits;
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holeoff = offset;
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do {
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ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
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if (ret < 0) {
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inode_unlock(inode);
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return ret;
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}
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/* Found a hole? */
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if (ret == 0 || es.es_lblk > last) {
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if (last != start)
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holeoff = (loff_t)last << blkbits;
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break;
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}
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/*
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* If there is a unwritten extent at this offset,
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* it will be as a data or a hole according to page
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* cache that has data or not.
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*/
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if (ext4_es_is_unwritten(&es) &&
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ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
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last + es.es_len, &holeoff))
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break;
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last += es.es_len;
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holeoff = (loff_t)last << blkbits;
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cond_resched();
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} while (last <= end);
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inode_unlock(inode);
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if (holeoff > isize)
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holeoff = isize;
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return vfs_setpos(file, holeoff, maxsize);
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}
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/*
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* ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
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* by calling generic_file_llseek_size() with the appropriate maxbytes
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@@ -695,18 +454,24 @@ loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
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maxbytes = inode->i_sb->s_maxbytes;
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switch (whence) {
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case SEEK_SET:
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case SEEK_CUR:
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case SEEK_END:
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default:
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return generic_file_llseek_size(file, offset, whence,
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maxbytes, i_size_read(inode));
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case SEEK_DATA:
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return ext4_seek_data(file, offset, maxbytes);
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case SEEK_HOLE:
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return ext4_seek_hole(file, offset, maxbytes);
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inode_lock_shared(inode);
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offset = iomap_seek_hole(inode, offset, &ext4_iomap_ops);
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inode_unlock_shared(inode);
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break;
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case SEEK_DATA:
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inode_lock_shared(inode);
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offset = iomap_seek_data(inode, offset, &ext4_iomap_ops);
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inode_unlock_shared(inode);
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break;
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}
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return -EINVAL;
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if (offset < 0)
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return offset;
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return vfs_setpos(file, offset, maxbytes);
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}
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const struct file_operations ext4_file_operations = {
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