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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 2017-10-01 17:58:54 -04:00 committed by Theodore Ts'o
parent 7046ae3532
commit 545052e9e3
4 changed files with 49 additions and 327 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/ext4/Kconfig
View File

@ -37,6 +37,7 @@ config EXT4_FS
select CRC16
select CRYPTO
select CRYPTO_CRC32C
select FS_IOMAP
help
This is the next generation of the ext3 filesystem.

3
fs/ext4/ext4.h
View File

@ -2515,9 +2515,6 @@ extern void ext4_da_update_reserve_space(struct inode *inode,
int used, int quota_claim);
extern int ext4_issue_zeroout(struct inode *inode, ext4_lblk_t lblk,
ext4_fsblk_t pblk, ext4_lblk_t len);
extern int ext4_get_next_extent(struct inode *inode, ext4_lblk_t lblk,
unsigned int map_len,
struct extent_status *result);
/* indirect.c */
extern int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,

263
fs/ext4/file.c
View File

@ -20,6 +20,7 @@
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/mount.h>
#include <linux/path.h>
#include <linux/dax.h>
@ -437,248 +438,6 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
return dquot_file_open(inode, 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;
unsigned long nr_pages;
nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping,
&index, end);
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;
}
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 (lastoff + bh->b_size <= startoff)
goto next;
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;
}
next:
lastoff += bh->b_size;
bh = bh->b_this_page;
} while (bh != head);
}
lastoff = page_offset(page) + PAGE_SIZE;
unlock_page(page);
}
pagevec_release(&pvec);
} while (index <= end);
/* There are no pages upto endoff - that would be a hole in there. */
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)
{
struct inode *inode = file->f_mapping->host;
struct extent_status es;
ext4_lblk_t start, last, end;
loff_t dataoff, isize;
int blkbits;
int ret;
inode_lock(inode);
isize = i_size_read(inode);
if (offset < 0 || offset >= isize) {
inode_unlock(inode);
return -ENXIO;
}
blkbits = inode->i_sb->s_blocksize_bits;
start = offset >> blkbits;
last = start;
end = isize >> blkbits;
dataoff = offset;
do {
ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
if (ret <= 0) {
/* No extent found -> no data */
if (ret == 0)
ret = -ENXIO;
inode_unlock(inode);
return ret;
}
last = es.es_lblk;
if (last != start)
dataoff = (loff_t)last << blkbits;
if (!ext4_es_is_unwritten(&es))
break;
/*
* If there is a unwritten extent at this offset,
* 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))
break;
last += es.es_len;
dataoff = (loff_t)last << blkbits;
cond_resched();
} while (last <= end);
inode_unlock(inode);
if (dataoff > isize)
return -ENXIO;
return vfs_setpos(file, dataoff, maxsize);
}
/*
* ext4_seek_hole() retrieves the offset for SEEK_HOLE.
*/
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;
int blkbits;
int ret;
inode_lock(inode);
isize = i_size_read(inode);
if (offset < 0 || offset >= isize) {
inode_unlock(inode);
return -ENXIO;
}
blkbits = inode->i_sb->s_blocksize_bits;
start = offset >> blkbits;
last = start;
end = isize >> blkbits;
holeoff = offset;
do {
ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
if (ret < 0) {
inode_unlock(inode);
return ret;
}
/* Found a hole? */
if (ret == 0 || es.es_lblk > last) {
if (last != start)
holeoff = (loff_t)last << blkbits;
break;
}
/*
* If there is a unwritten extent at this offset,
* 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;
last += es.es_len;
holeoff = (loff_t)last << blkbits;
cond_resched();
} while (last <= end);
inode_unlock(inode);
if (holeoff > isize)
holeoff = isize;
return vfs_setpos(file, holeoff, maxsize);
}
/*
* ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
* by calling generic_file_llseek_size() with the appropriate maxbytes
@ -695,18 +454,24 @@ loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
maxbytes = inode->i_sb->s_maxbytes;
switch (whence) {
case SEEK_SET:
case SEEK_CUR:
case SEEK_END:
default:
return generic_file_llseek_size(file, offset, whence,
maxbytes, i_size_read(inode));
case SEEK_DATA:
return ext4_seek_data(file, offset, maxbytes);
case SEEK_HOLE:
return ext4_seek_hole(file, offset, maxbytes);
inode_lock_shared(inode);
offset = iomap_seek_hole(inode, offset, &ext4_iomap_ops);
inode_unlock_shared(inode);
break;
case SEEK_DATA:
inode_lock_shared(inode);
offset = iomap_seek_data(inode, offset, &ext4_iomap_ops);
inode_unlock_shared(inode);
break;
}
return -EINVAL;
if (offset < 0)
return offset;
return vfs_setpos(file, offset, maxbytes);
}
const struct file_operations ext4_file_operations = {

109
fs/ext4/inode.c
View File

@ -3393,7 +3393,6 @@ static int ext4_releasepage(struct page *page, gfp_t wait)
return try_to_free_buffers(page);
}
#ifdef CONFIG_FS_DAX
static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
unsigned flags, struct iomap *iomap)
{
@ -3402,6 +3401,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
unsigned long first_block = offset >> blkbits;
unsigned long last_block = (offset + length - 1) >> blkbits;
struct ext4_map_blocks map;
bool delalloc = false;
int ret;
@ -3422,9 +3422,33 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
map.m_lblk = first_block;
map.m_len = last_block - first_block + 1;
if (!(flags & IOMAP_WRITE)) {
if (flags & IOMAP_REPORT) {
ret = ext4_map_blocks(NULL, inode, &map, 0);
} else {
if (ret < 0)
return ret;
if (ret == 0) {
ext4_lblk_t end = map.m_lblk + map.m_len - 1;
struct extent_status es;
ext4_es_find_delayed_extent_range(inode, map.m_lblk, end, &es);
if (!es.es_len || es.es_lblk > end) {
/* entire range is a hole */
} else if (es.es_lblk > map.m_lblk) {
/* range starts with a hole */
map.m_len = es.es_lblk - map.m_lblk;
} else {
ext4_lblk_t offs = 0;
if (es.es_lblk < map.m_lblk)
offs = map.m_lblk - es.es_lblk;
map.m_lblk = es.es_lblk + offs;
map.m_len = es.es_len - offs;
delalloc = true;
}
}
} else if (flags & IOMAP_WRITE) {
int dio_credits;
handle_t *handle;
int retries = 0;
@ -3475,17 +3499,21 @@ retry:
}
}
ext4_journal_stop(handle);
} else {
ret = ext4_map_blocks(NULL, inode, &map, 0);
if (ret < 0)
return ret;
}
iomap->flags = 0;
iomap->bdev = inode->i_sb->s_bdev;
iomap->dax_dev = sbi->s_daxdev;
iomap->offset = first_block << blkbits;
iomap->length = (u64)map.m_len << blkbits;
if (ret == 0) {
iomap->type = IOMAP_HOLE;
iomap->type = delalloc ? IOMAP_DELALLOC : IOMAP_HOLE;
iomap->addr = IOMAP_NULL_ADDR;
iomap->length = (u64)map.m_len << blkbits;
} else {
if (map.m_flags & EXT4_MAP_MAPPED) {
iomap->type = IOMAP_MAPPED;
@ -3496,11 +3524,11 @@ retry:
return -EIO;
}
iomap->addr = (u64)map.m_pblk << blkbits;
iomap->length = (u64)map.m_len << blkbits;
}
if (map.m_flags & EXT4_MAP_NEW)
iomap->flags |= IOMAP_F_NEW;
return 0;
}
@ -3561,8 +3589,6 @@ const struct iomap_ops ext4_iomap_ops = {
.iomap_end = ext4_iomap_end,
};
#endif
static int ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
ssize_t size, void *private)
{
@ -6118,70 +6144,3 @@ int ext4_filemap_fault(struct vm_fault *vmf)
return err;
}
/*
* Find the first extent at or after @lblk in an inode that is not a hole.
* Search for @map_len blocks at most. The extent is returned in @result.
*
* The function returns 1 if we found an extent. The function returns 0 in
* case there is no extent at or after @lblk and in that case also sets
* @result->es_len to 0. In case of error, the error code is returned.
*/
int ext4_get_next_extent(struct inode *inode, ext4_lblk_t lblk,
unsigned int map_len, struct extent_status *result)
{
struct ext4_map_blocks map;
struct extent_status es = {};
int ret;
map.m_lblk = lblk;
map.m_len = map_len;
/*
* For non-extent based files this loop may iterate several times since
* we do not determine full hole size.
*/
while (map.m_len > 0) {
ret = ext4_map_blocks(NULL, inode, &map, 0);
if (ret < 0)
return ret;
/* There's extent covering m_lblk? Just return it. */
if (ret > 0) {
int status;
ext4_es_store_pblock(result, map.m_pblk);
result->es_lblk = map.m_lblk;
result->es_len = map.m_len;
if (map.m_flags & EXT4_MAP_UNWRITTEN)
status = EXTENT_STATUS_UNWRITTEN;
else
status = EXTENT_STATUS_WRITTEN;
ext4_es_store_status(result, status);
return 1;
}
ext4_es_find_delayed_extent_range(inode, map.m_lblk,
map.m_lblk + map.m_len - 1,
&es);
/* Is delalloc data before next block in extent tree? */
if (es.es_len && es.es_lblk < map.m_lblk + map.m_len) {
ext4_lblk_t offset = 0;
if (es.es_lblk < lblk)
offset = lblk - es.es_lblk;
result->es_lblk = es.es_lblk + offset;
ext4_es_store_pblock(result,
ext4_es_pblock(&es) + offset);
result->es_len = es.es_len - offset;
ext4_es_store_status(result, ext4_es_status(&es));
return 1;
}
/* There's a hole at m_lblk, advance us after it */
map.m_lblk += map.m_len;
map_len -= map.m_len;
map.m_len = map_len;
cond_resched();
}
result->es_len = 0;
return 0;
}