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Subject[PATCH v4 08/16] iomap: Use mapping_seek_hole_data
Date
Enhance mapping_seek_hole_data() to handle partially uptodate pages and
convert the iomap seek code to call it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/iomap/seek.c | 125 +++++-------------------------------------------
mm/filemap.c | 37 ++++++++++++--
2 files changed, 43 insertions(+), 119 deletions(-)

diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
index 107ee80c3568..dab1b02eba5b 100644
--- a/fs/iomap/seek.c
+++ b/fs/iomap/seek.c
@@ -10,122 +10,17 @@
#include <linux/pagemap.h>
#include <linux/pagevec.h>

-/*
- * Seek for SEEK_DATA / SEEK_HOLE within @page, starting at @lastoff.
- * Returns true if found and updates @lastoff to the offset in file.
- */
-static bool
-page_seek_hole_data(struct inode *inode, struct page *page, loff_t *lastoff,
- int whence)
-{
- const struct address_space_operations *ops = inode->i_mapping->a_ops;
- unsigned int bsize = i_blocksize(inode), off;
- bool seek_data = whence == SEEK_DATA;
- loff_t poff = page_offset(page);
-
- if (WARN_ON_ONCE(*lastoff >= poff + PAGE_SIZE))
- return false;
-
- if (*lastoff < poff) {
- /*
- * Last offset smaller than the start of the page means we found
- * a hole:
- */
- if (whence == SEEK_HOLE)
- return true;
- *lastoff = poff;
- }
-
- /*
- * Just check the page unless we can and should check block ranges:
- */
- if (bsize == PAGE_SIZE || !ops->is_partially_uptodate)
- return PageUptodate(page) == seek_data;
-
- lock_page(page);
- if (unlikely(page->mapping != inode->i_mapping))
- goto out_unlock_not_found;
-
- for (off = 0; off < PAGE_SIZE; off += bsize) {
- if (offset_in_page(*lastoff) >= off + bsize)
- continue;
- if (ops->is_partially_uptodate(page, off, bsize) == seek_data) {
- unlock_page(page);
- return true;
- }
- *lastoff = poff + off + bsize;
- }
-
-out_unlock_not_found:
- unlock_page(page);
- return false;
-}
-
-/*
- * Seek for SEEK_DATA / SEEK_HOLE in the page cache.
- *
- * Within unwritten extents, the page cache determines which parts are holes
- * and which are data: uptodate buffer heads count as data; everything else
- * counts as a hole.
- *
- * Returns the resulting offset on successs, and -ENOENT otherwise.
- */
static loff_t
-page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
- int whence)
-{
- pgoff_t index = offset >> PAGE_SHIFT;
- pgoff_t end = DIV_ROUND_UP(offset + length, PAGE_SIZE);
- loff_t lastoff = offset;
- struct pagevec pvec;
-
- if (length <= 0)
- return -ENOENT;
-
- pagevec_init(&pvec);
-
- do {
- unsigned nr_pages, i;
-
- nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping, &index,
- end - 1);
- if (nr_pages == 0)
- break;
-
- for (i = 0; i < nr_pages; i++) {
- struct page *page = pvec.pages[i];
-
- if (page_seek_hole_data(inode, page, &lastoff, whence))
- goto check_range;
- lastoff = page_offset(page) + PAGE_SIZE;
- }
- pagevec_release(&pvec);
- } while (index < end);
-
- /* When no page at lastoff and we are not done, we found a hole. */
- if (whence != SEEK_HOLE)
- goto not_found;
-
-check_range:
- if (lastoff < offset + length)
- goto out;
-not_found:
- lastoff = -ENOENT;
-out:
- pagevec_release(&pvec);
- return lastoff;
-}
-
-
-static loff_t
-iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
+iomap_seek_hole_actor(struct inode *inode, loff_t start, loff_t length,
void *data, struct iomap *iomap, struct iomap *srcmap)
{
+ loff_t offset = start;
+
switch (iomap->type) {
case IOMAP_UNWRITTEN:
- offset = page_cache_seek_hole_data(inode, offset, length,
- SEEK_HOLE);
- if (offset < 0)
+ offset = mapping_seek_hole_data(inode->i_mapping, start,
+ start + length, SEEK_HOLE);
+ if (offset == start + length)
return length;
fallthrough;
case IOMAP_HOLE:
@@ -164,15 +59,17 @@ iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
EXPORT_SYMBOL_GPL(iomap_seek_hole);

static loff_t
-iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
+iomap_seek_data_actor(struct inode *inode, loff_t start, loff_t length,
void *data, struct iomap *iomap, struct iomap *srcmap)
{
+ loff_t offset = start;
+
switch (iomap->type) {
case IOMAP_HOLE:
return length;
case IOMAP_UNWRITTEN:
- offset = page_cache_seek_hole_data(inode, offset, length,
- SEEK_DATA);
+ offset = mapping_seek_hole_data(inode->i_mapping, start,
+ start + length, SEEK_DATA);
if (offset < 0)
return length;
fallthrough;
diff --git a/mm/filemap.c b/mm/filemap.c
index ab7103eb7e11..ef7411ea3f91 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2586,11 +2586,36 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
}
EXPORT_SYMBOL(generic_file_read_iter);

-static inline bool page_seek_match(struct page *page, bool seek_data)
+static inline loff_t page_seek_hole_data(struct xa_state *xas,
+ struct address_space *mapping, struct page *page,
+ loff_t start, loff_t end, bool seek_data)
{
+ const struct address_space_operations *ops = mapping->a_ops;
+ size_t offset, bsz = i_blocksize(mapping->host);
+
if (xa_is_value(page) || PageUptodate(page))
- return seek_data;
- return !seek_data;
+ return seek_data ? start : end;
+ if (!ops->is_partially_uptodate)
+ return seek_data ? end : start;
+
+ xas_pause(xas);
+ rcu_read_unlock();
+ lock_page(page);
+ if (unlikely(page->mapping != mapping))
+ goto unlock;
+
+ offset = offset_in_thp(page, start) & ~(bsz - 1);
+
+ do {
+ if (ops->is_partially_uptodate(page, offset, bsz) == seek_data)
+ break;
+ start = (start + bsz) & ~(bsz - 1);
+ offset += bsz;
+ } while (offset < thp_size(page));
+unlock:
+ unlock_page(page);
+ rcu_read_lock();
+ return start;
}

static inline
@@ -2640,9 +2665,11 @@ loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
start = pos;
}

- if (page_seek_match(page, seek_data))
+ pos += seek_page_size(&xas, page);
+ start = page_seek_hole_data(&xas, mapping, page, start, pos,
+ seek_data);
+ if (start < pos)
goto unlock;
- start = pos + seek_page_size(&xas, page);
put_page(page);
}
rcu_read_unlock();
--
2.28.0
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