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xfs: 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.

Based on patches from Andreas Gruenbacher <agruenba@redhat.com>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2017-06-29 11:43:21 -07:00 committed by Darrick J. Wong
parent 0ed3b0d45f
commit 9b2970aacf
2 changed files with 14 additions and 364 deletions
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375
fs/xfs/xfs_file.c
View File

@ -954,378 +954,31 @@ xfs_file_readdir(
return xfs_readdir(NULL, ip, ctx, bufsize);
}
/*
* This type is designed to indicate the type of offset we would like
* to search from page cache for xfs_seek_hole_data().
*/
enum {
HOLE_OFF = 0,
DATA_OFF,
};
/*
* Lookup the desired type of offset from the given page.
*
* On success, return true and the offset argument will point to the
* start of the region that was found. Otherwise this function will
* return false and keep the offset argument unchanged.
*/
STATIC bool
xfs_lookup_buffer_offset(
struct page *page,
loff_t *offset,
unsigned int type)
{
loff_t lastoff = page_offset(page);
bool found = false;
struct buffer_head *bh, *head;
bh = head = page_buffers(page);
do {
/*
* Unwritten extents that have data in the page
* cache covering them can be identified by the
* BH_Unwritten state flag. Pages with multiple
* buffers might have a mix of holes, data and
* unwritten extents - any buffer with valid
* data in it should have BH_Uptodate flag set
* on it.
*/
if (buffer_unwritten(bh) ||
buffer_uptodate(bh)) {
if (type == DATA_OFF)
found = true;
} else {
if (type == HOLE_OFF)
found = true;
}
if (found) {
*offset = lastoff;
break;
}
lastoff += bh->b_size;
} while ((bh = bh->b_this_page) != head);
return found;
}
/*
* This routine is called to find out and return a data or hole offset
* from the page cache for unwritten extents according to the desired
* type for xfs_seek_hole_data().
*
* The argument offset is used to tell where we start to search from the
* page cache. Map is used to figure out the end points of the range to
* lookup pages.
*
* Return true if the desired type of offset was found, and the argument
* offset is filled with that address. Otherwise, return false and keep
* offset unchanged.
*/
STATIC bool
xfs_find_get_desired_pgoff(
struct inode *inode,
struct xfs_bmbt_irec *map,
unsigned int type,
loff_t *offset)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
struct pagevec pvec;
pgoff_t index;
pgoff_t end;
loff_t endoff;
loff_t startoff = *offset;
loff_t lastoff = startoff;
bool found = false;
pagevec_init(&pvec, 0);
index = startoff >> PAGE_SHIFT;
endoff = XFS_FSB_TO_B(mp, map->br_startoff + map->br_blockcount);
end = (endoff - 1) >> PAGE_SHIFT;
do {
int want;
unsigned nr_pages;
unsigned int i;
want = min_t(pgoff_t, end - index, PAGEVEC_SIZE - 1) + 1;
nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
want);
if (nr_pages == 0)
break;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
loff_t b_offset;
/*
* At this point, the page may be truncated or
* invalidated (changing page->mapping to NULL),
* or even swizzled back from swapper_space to tmpfs
* file mapping. However, page->index will not change
* because we have a reference on the page.
*
* If current page offset is beyond where we've ended,
* we've found a hole.
*/
if (type == HOLE_OFF && lastoff < endoff &&
lastoff < page_offset(pvec.pages[i])) {
found = true;
*offset = lastoff;
goto out;
}
/* Searching done if the page index is out of range. */
if (page->index > end)
goto out;
lock_page(page);
/*
* Page truncated or invalidated(page->mapping == NULL).
* We can freely skip it and proceed to check the next
* page.
*/
if (unlikely(page->mapping != inode->i_mapping)) {
unlock_page(page);
continue;
}
if (!page_has_buffers(page)) {
unlock_page(page);
continue;
}
found = xfs_lookup_buffer_offset(page, &b_offset, type);
if (found) {
/*
* The found offset may be less than the start
* point to search if this is the first time to
* come here.
*/
*offset = max_t(loff_t, startoff, b_offset);
unlock_page(page);
goto out;
}
/*
* We either searching data but nothing was found, or
* searching hole but found a data buffer. In either
* case, probably the next page contains the desired
* things, update the last offset to it so.
*/
lastoff = page_offset(page) + PAGE_SIZE;
unlock_page(page);
}
/*
* The number of returned pages less than our desired, search
* done.
*/
if (nr_pages < want)
break;
index = pvec.pages[i - 1]->index + 1;
pagevec_release(&pvec);
} while (index <= end);
/* No page at lastoff and we are not done - we found a hole. */
if (type == HOLE_OFF && lastoff < endoff) {
*offset = lastoff;
found = true;
}
out:
pagevec_release(&pvec);
return found;
}
/*
* caller must lock inode with xfs_ilock_data_map_shared,
* can we craft an appropriate ASSERT?
*
* end is because the VFS-level lseek interface is defined such that any
* offset past i_size shall return -ENXIO, but we use this for quota code
* which does not maintain i_size, and we want to SEEK_DATA past i_size.
*/
loff_t
__xfs_seek_hole_data(
struct inode *inode,
loff_t start,
loff_t end,
int whence)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
loff_t uninitialized_var(offset);
xfs_fileoff_t fsbno;
xfs_filblks_t lastbno;
int error;
if (start >= end) {
error = -ENXIO;
goto out_error;
}
/*
* Try to read extents from the first block indicated
* by fsbno to the end block of the file.
*/
fsbno = XFS_B_TO_FSBT(mp, start);
lastbno = XFS_B_TO_FSB(mp, end);
for (;;) {
struct xfs_bmbt_irec map[2];
int nmap = 2;
unsigned int i;
error = xfs_bmapi_read(ip, fsbno, lastbno - fsbno, map, &nmap,
XFS_BMAPI_ENTIRE);
if (error)
goto out_error;
/* No extents at given offset, must be beyond EOF */
if (nmap == 0) {
error = -ENXIO;
goto out_error;
}
for (i = 0; i < nmap; i++) {
offset = max_t(loff_t, start,
XFS_FSB_TO_B(mp, map[i].br_startoff));
/* Landed in the hole we wanted? */
if (whence == SEEK_HOLE &&
map[i].br_startblock == HOLESTARTBLOCK)
goto out;
/* Landed in the data extent we wanted? */
if (whence == SEEK_DATA &&
(map[i].br_startblock == DELAYSTARTBLOCK ||
(map[i].br_state == XFS_EXT_NORM &&
!isnullstartblock(map[i].br_startblock))))
goto out;
/*
* Landed in an unwritten extent, try to search
* for hole or data from page cache.
*/
if (map[i].br_state == XFS_EXT_UNWRITTEN) {
if (xfs_find_get_desired_pgoff(inode, &map[i],
whence == SEEK_HOLE ? HOLE_OFF : DATA_OFF,
&offset))
goto out;
}
}
/*
* We only received one extent out of the two requested. This
* means we've hit EOF and didn't find what we are looking for.
*/
if (nmap == 1) {
/*
* If we were looking for a hole, set offset to
* the end of the file (i.e., there is an implicit
* hole at the end of any file).
*/
if (whence == SEEK_HOLE) {
offset = end;
break;
}
/*
* If we were looking for data, it's nowhere to be found
*/
ASSERT(whence == SEEK_DATA);
error = -ENXIO;
goto out_error;
}
ASSERT(i > 1);
/*
* Nothing was found, proceed to the next round of search
* if the next reading offset is not at or beyond EOF.
*/
fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
start = XFS_FSB_TO_B(mp, fsbno);
if (start >= end) {
if (whence == SEEK_HOLE) {
offset = end;
break;
}
ASSERT(whence == SEEK_DATA);
error = -ENXIO;
goto out_error;
}
}
out:
/*
* If at this point we have found the hole we wanted, the returned
* offset may be bigger than the file size as it may be aligned to
* page boundary for unwritten extents. We need to deal with this
* situation in particular.
*/
if (whence == SEEK_HOLE)
offset = min_t(loff_t, offset, end);
return offset;
out_error:
return error;
}
STATIC loff_t
xfs_seek_hole_data(
struct file *file,
loff_t start,
int whence)
{
struct inode *inode = file->f_mapping->host;
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
uint lock;
loff_t offset, end;
int error = 0;
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
lock = xfs_ilock_data_map_shared(ip);
end = i_size_read(inode);
offset = __xfs_seek_hole_data(inode, start, end, whence);
if (offset < 0) {
error = offset;
goto out_unlock;
}
offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
out_unlock:
xfs_iunlock(ip, lock);
if (error)
return error;
return offset;
}
STATIC loff_t
xfs_file_llseek(
struct file *file,
loff_t offset,
int whence)
{
struct inode *inode = file->f_mapping->host;
if (XFS_FORCED_SHUTDOWN(XFS_I(inode)->i_mount))
return -EIO;
switch (whence) {
case SEEK_END:
case SEEK_CUR:
case SEEK_SET:
default:
return generic_file_llseek(file, offset, whence);
case SEEK_HOLE:
offset = iomap_seek_hole(inode, offset, &xfs_iomap_ops);
break;
case SEEK_DATA:
return xfs_seek_hole_data(file, offset, whence);
default:
return -EINVAL;
offset = iomap_seek_data(inode, offset, &xfs_iomap_ops);
break;
}
if (offset < 0)
return offset;
return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
}
/*

3
fs/xfs/xfs_inode.h
View File

@ -445,9 +445,6 @@ int xfs_zero_eof(struct xfs_inode *ip, xfs_off_t offset,
xfs_fsize_t isize, bool *did_zeroing);
int xfs_zero_range(struct xfs_inode *ip, xfs_off_t pos, xfs_off_t count,
bool *did_zero);
loff_t __xfs_seek_hole_data(struct inode *inode, loff_t start,
loff_t eof, int whence);
/* from xfs_iops.c */
extern void xfs_setup_inode(struct xfs_inode *ip);