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Message-Id: <1498177173-30798-2-git-send-email-agruenba@redhat.com>
Date: Fri, 23 Jun 2017 02:19:32 +0200
From: Andreas Gruenbacher <agruenba@...hat.com>
To: linux-fsdevel@...r.kernel.org
Cc: Andreas Gruenbacher <agruenba@...hat.com>,
linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
Jan Kara <jack@...e.cz>
Subject: [PATCH 2/3] ext4: Switch to page_cache_seek_hole_data
Fix SEEK_HOLE / SEEK_DATA when a page fits more than two filesystem
blocks (see the commit that introduces page_cache_seek_hole_data).
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
fs/ext4/file.c | 144 ++++++---------------------------------------------------
1 file changed, 13 insertions(+), 131 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 02ce7e7..d0b0862 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -439,129 +439,6 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
}
/*
- * Here we use ext4_map_blocks() to get a block mapping for a extent-based
- * file rather than ext4_ext_walk_space() because we can introduce
- * SEEK_DATA/SEEK_HOLE for block-mapped and extent-mapped file at the same
- * function. When extent status tree has been fully implemented, it will
- * track all extent status for a file and we can directly use it to
- * retrieve the offset for SEEK_DATA/SEEK_HOLE.
- */
-
-/*
- * When we retrieve the offset for SEEK_DATA/SEEK_HOLE, we would need to
- * lookup page cache to check whether or not there has some data between
- * [startoff, endoff] because, if this range contains an unwritten extent,
- * we determine this extent as a data or a hole according to whether the
- * page cache has data or not.
- */
-static int ext4_find_unwritten_pgoff(struct inode *inode,
- int whence,
- ext4_lblk_t end_blk,
- loff_t *offset)
-{
- struct pagevec pvec;
- unsigned int blkbits;
- pgoff_t index;
- pgoff_t end;
- loff_t endoff;
- loff_t startoff;
- loff_t lastoff;
- int found = 0;
-
- blkbits = inode->i_sb->s_blocksize_bits;
- startoff = *offset;
- lastoff = startoff;
- endoff = (loff_t)end_blk << blkbits;
-
- index = startoff >> PAGE_SHIFT;
- end = (endoff - 1) >> PAGE_SHIFT;
-
- pagevec_init(&pvec, 0);
- do {
- int i, num;
- unsigned long nr_pages;
-
- num = min_t(pgoff_t, end - index, PAGEVEC_SIZE - 1) + 1;
- nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
- (pgoff_t)num);
- if (nr_pages == 0)
- break;
-
- for (i = 0; i < nr_pages; i++) {
- struct page *page = pvec.pages[i];
- struct buffer_head *bh, *head;
-
- /*
- * If current offset is smaller than the page offset,
- * there is a hole at this offset.
- */
- if (whence == SEEK_HOLE && lastoff < endoff &&
- lastoff < page_offset(pvec.pages[i])) {
- found = 1;
- *offset = lastoff;
- goto out;
- }
-
- if (page->index > end)
- goto out;
-
- lock_page(page);
-
- if (unlikely(page->mapping != inode->i_mapping)) {
- unlock_page(page);
- continue;
- }
-
- if (!page_has_buffers(page)) {
- unlock_page(page);
- continue;
- }
-
- if (page_has_buffers(page)) {
- lastoff = page_offset(page);
- bh = head = page_buffers(page);
- do {
- if (buffer_uptodate(bh) ||
- buffer_unwritten(bh)) {
- if (whence == SEEK_DATA)
- found = 1;
- } else {
- if (whence == SEEK_HOLE)
- found = 1;
- }
- if (found) {
- *offset = max_t(loff_t,
- startoff, lastoff);
- unlock_page(page);
- goto out;
- }
- lastoff += bh->b_size;
- bh = bh->b_this_page;
- } while (bh != head);
- }
-
- lastoff = page_offset(page) + PAGE_SIZE;
- unlock_page(page);
- }
-
- /* The no. of pages is less than our desired, we are done. */
- if (nr_pages < num)
- break;
-
- index = pvec.pages[i - 1]->index + 1;
- pagevec_release(&pvec);
- } while (index <= end);
-
- if (whence == SEEK_HOLE && lastoff < endoff) {
- found = 1;
- *offset = lastoff;
- }
-out:
- pagevec_release(&pvec);
- return found;
-}
-
-/*
* ext4_seek_data() retrieves the offset for SEEK_DATA.
*/
static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
@@ -569,7 +446,7 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
struct inode *inode = file->f_mapping->host;
struct extent_status es;
ext4_lblk_t start, last, end;
- loff_t dataoff, isize;
+ loff_t dataoff, length, isize;
int blkbits;
int ret;
@@ -608,8 +485,10 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
* it will be as a data or a hole according to page
* cache that has data or not.
*/
- if (ext4_find_unwritten_pgoff(inode, SEEK_DATA,
- es.es_lblk + es.es_len, &dataoff))
+ length = ((loff_t)(last + es.es_len) << blkbits) - dataoff;
+ dataoff = page_cache_seek_hole_data(inode, dataoff,
+ length, SEEK_DATA);
+ if (dataoff >= 0)
break;
last += es.es_len;
dataoff = (loff_t)last << blkbits;
@@ -632,7 +511,7 @@ static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
struct inode *inode = file->f_mapping->host;
struct extent_status es;
ext4_lblk_t start, last, end;
- loff_t holeoff, isize;
+ loff_t holeoff, length, isize;
int blkbits;
int ret;
@@ -667,10 +546,13 @@ static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
* it will be as a data or a hole according to page
* cache that has data or not.
*/
- if (ext4_es_is_unwritten(&es) &&
- ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
- last + es.es_len, &holeoff))
- break;
+ if (ext4_es_is_unwritten(&es)) {
+ length = ((loff_t)(last + es.es_len) << blkbits) - holeoff;
+ holeoff = page_cache_seek_hole_data(inode, holeoff,
+ length, SEEK_HOLE);
+ if (holeoff >= 0)
+ break;
+ }
last += es.es_len;
holeoff = (loff_t)last << blkbits;
--
2.7.5
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