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xfs: use shmem_get_folio in in xfile_load

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Switch to using shmem_get_folio in xfile_load instead of using
shmem_read_mapping_page_gfp.  This gets us support for large folios
and also optimized reading from unallocated space, as
shmem_get_folio with SGP_READ won't allocate a page for them just
to zero the content.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
This commit is contained in:
Christoph Hellwig 2024-02-19 07:27:25 +01:00 committed by Chandan Babu R
parent fd2634e2dd
commit e97d70a573
1 changed files with 26 additions and 35 deletions
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61
fs/xfs/scrub/xfile.c
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@ -34,13 +34,6 @@
* xfiles assume that the caller will handle all required concurrency
* management; standard vfs locks (freezer and inode) are not taken. Reads
* and writes are satisfied directly from the page cache.
*
* NOTE: The current shmemfs implementation has a quirk that in-kernel reads
* of a hole cause a page to be mapped into the file. If you are going to
* create a sparse xfile, please be careful about reading from uninitialized
* parts of the file. These pages are !Uptodate and will eventually be
* reclaimed if not written, but in the short term this boosts memory
* consumption.
*/
/*
@ -118,10 +111,7 @@ xfile_load(
loff_t pos)
{
struct inode *inode = file_inode(xf->file);
struct address_space *mapping = inode->i_mapping;
struct page *page = NULL;
unsigned int pflags;
int error = 0;
if (count > MAX_RW_COUNT)
return -ENOMEM;
@ -132,43 +122,44 @@ xfile_load(
pflags = memalloc_nofs_save();
while (count > 0) {
struct folio *folio;
unsigned int len;
unsigned int offset;
len = min_t(ssize_t, count, PAGE_SIZE - offset_in_page(pos));
/*
* In-kernel reads of a shmem file cause it to allocate a page
* if the mapping shows a hole. Therefore, if we hit ENOMEM
* we can continue by zeroing the caller's buffer.
*/
page = shmem_read_mapping_page_gfp(mapping, pos >> PAGE_SHIFT,
__GFP_NOWARN);
if (IS_ERR(page)) {
error = PTR_ERR(page);
if (error != -ENOMEM) {
error = -ENOMEM;
if (shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
SGP_READ) < 0)
break;
if (!folio) {
/*
* No data stored at this offset, just zero the output
* buffer until the next page boundary.
*/
len = min_t(ssize_t, count,
PAGE_SIZE - offset_in_page(pos));
memset(buf, 0, len);
} else {
if (filemap_check_wb_err(inode->i_mapping, 0)) {
folio_unlock(folio);
folio_put(folio);
break;
}
memset(buf, 0, len);
goto advance;
offset = offset_in_folio(folio, pos);
len = min_t(ssize_t, count, folio_size(folio) - offset);
memcpy(buf, folio_address(folio) + offset, len);
folio_unlock(folio);
folio_put(folio);
}
/*
* xfile pages must never be mapped into userspace, so
* we skip the dcache flush.
*/
memcpy(buf, page_address(page) + offset_in_page(pos), len);
put_page(page);
advance:
count -= len;
pos += len;
buf += len;
}
memalloc_nofs_restore(pflags);
return error;
if (count)
return -ENOMEM;
return 0;
}
/*