ping ?
On 2018/12/6 9:14, Hou Tao wrote:
> ping ?
>
> On 2018/12/4 10:08, Hou Tao wrote:
>> There is no need to disable __GFP_FS in ->readpage:
>> * It's a read-only fs, so there will be no dirty/writeback page and
>> there will be no deadlock against the caller's locked page
>> * It just allocates one page, so compaction will not be invoked
>> * It doesn't take any inode lock, so the reclamation of inode will be fine
>>
>> And no __GFP_FS may lead to hang in __alloc_pages_slowpath() if a
>> squashfs page fault occurs in the context of a memory hogger, because
>> the hogger will not be killed due to the logic in __alloc_pages_may_oom().
>>
>> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
>> ---
>> fs/squashfs/file.c | 3 ++-
>> fs/squashfs/file_direct.c | 4 +++-
>> fs/squashfs/squashfs_fs_f.h | 25 +++++++++++++++++++++++++
>> 3 files changed, 30 insertions(+), 2 deletions(-)
>> create mode 100644 fs/squashfs/squashfs_fs_f.h
>>
>> diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
>> index f1c1430ae721..8603dda4a719 100644
>> --- a/fs/squashfs/file.c
>> +++ b/fs/squashfs/file.c
>> @@ -51,6 +51,7 @@
>> #include "squashfs_fs.h"
>> #include "squashfs_fs_sb.h"
>> #include "squashfs_fs_i.h"
>> +#include "squashfs_fs_f.h"
>> #include "squashfs.h"
>>
>> /*
>> @@ -414,7 +415,7 @@ void squashfs_copy_cache(struct page *page, struct squashfs_cache_entry *buffer,
>> TRACE("bytes %d, i %d, available_bytes %d\n", bytes, i, avail);
>>
>> push_page = (i == page->index) ? page :
>> - grab_cache_page_nowait(page->mapping, i);
>> + squashfs_grab_cache_page_nowait(page->mapping, i);
>>
>> if (!push_page)
>> continue;
>> diff --git a/fs/squashfs/file_direct.c b/fs/squashfs/file_direct.c
>> index 80db1b86a27c..a0fdd6215348 100644
>> --- a/fs/squashfs/file_direct.c
>> +++ b/fs/squashfs/file_direct.c
>> @@ -17,6 +17,7 @@
>> #include "squashfs_fs.h"
>> #include "squashfs_fs_sb.h"
>> #include "squashfs_fs_i.h"
>> +#include "squashfs_fs_f.h"
>> #include "squashfs.h"
>> #include "page_actor.h"
>>
>> @@ -60,7 +61,8 @@ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
>> /* Try to grab all the pages covered by the Squashfs block */
>> for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) {
>> page[i] = (n == target_page->index) ? target_page :
>> - grab_cache_page_nowait(target_page->mapping, n);
>> + squashfs_grab_cache_page_nowait(
>> + target_page->mapping, n);
>>
>> if (page[i] == NULL) {
>> missing_pages++;
>> diff --git a/fs/squashfs/squashfs_fs_f.h b/fs/squashfs/squashfs_fs_f.h
>> new file mode 100644
>> index 000000000000..fc5fb7aeb27d
>> --- /dev/null
>> +++ b/fs/squashfs/squashfs_fs_f.h
>> @@ -0,0 +1,25 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef SQUASHFS_FS_F
>> +#define SQUASHFS_FS_F
>> +
>> +/*
>> + * No need to use FGP_NOFS here:
>> + * 1. It's a read-only fs, so there will be no dirty/writeback page and
>> + * there will be no deadlock against the caller's locked page.
>> + * 2. It just allocates one page, so compaction will not be invoked.
>> + * 3. It doesn't take any inode lock, so the reclamation of inode
>> + * will be fine.
>> + *
>> + * And GFP_NOFS may lead to infinite loop in __alloc_pages_slowpath() if a
>> + * squashfs page fault occurs in the context of a memory hogger, because
>> + * the hogger will not be killed due to the logic in __alloc_pages_may_oom().
>> + */
>> +static inline struct page *
>> +squashfs_grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
>> +{
>> + return pagecache_get_page(mapping, index,
>> + FGP_LOCK|FGP_CREAT|FGP_NOWAIT,
>> + mapping_gfp_mask(mapping));
>> +}
>> +#endif
>> +
>>
>
>
> .
>
