From: "NeilBrown" <neilb@xxxxxxx> Subject: mm: introduce memalloc_retry_wait() Various places in the kernel - largely in filesystems - respond to a memory allocation failure by looping around and re-trying. Some of these cannot conveniently use __GFP_NOFAIL, for reasons such as: - a GFP_ATOMIC allocation, which __GFP_NOFAIL doesn't work on - a need to check for the process being signalled between failures - the possibility that other recovery actions could be performed - the allocation is quite deep in support code, and passing down an extra flag to say if __GFP_NOFAIL is wanted would be clumsy. Many of these currently use congestion_wait() which (in almost all cases) simply waits the given timeout - congestion isn't tracked for most devices. It isn't clear what the best delay is for loops, but it is clear that the various filesystems shouldn't be responsible for choosing a timeout. This patch introduces memalloc_retry_wait() with takes on that responsibility. Code that wants to retry a memory allocation can call this function passing the GFP flags that were used. It will wait however is appropriate. For now, it only considers __GFP_NORETRY and whatever gfpflags_allow_blocking() tests. If blocking is allowed without __GFP_NORETRY, then alloc_page either made some reclaim progress, or waited for a while, before failing. So there is no need for much further waiting. memalloc_retry_wait() will wait until the current jiffie ends. If this condition is not met, then alloc_page() won't have waited much if at all. In that case memalloc_retry_wait() waits about 200ms. This is the delay that most current loops uses. linux/sched/mm.h needs to be included in some files now, but linux/backing-dev.h does not. Link: https://lkml.kernel.org/r/163754371968.13692.1277530886009912421@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: NeilBrown <neilb@xxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: "Theodore Ts'o" <tytso@xxxxxxx> Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> Cc: Chao Yu <chao@xxxxxxxxxx> Cc: Darrick J. Wong <djwong@xxxxxxxxxx> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/ext4/extents.c | 8 +++----- fs/ext4/inline.c | 5 ++--- fs/ext4/page-io.c | 9 +++++---- fs/f2fs/data.c | 4 ++-- fs/f2fs/gc.c | 5 ++--- fs/f2fs/inode.c | 4 ++-- fs/f2fs/node.c | 4 ++-- fs/f2fs/recovery.c | 6 +++--- fs/f2fs/segment.c | 9 +++------ fs/f2fs/super.c | 5 ++--- fs/xfs/kmem.c | 3 +-- fs/xfs/xfs_buf.c | 2 +- include/linux/sched/mm.h | 26 ++++++++++++++++++++++++++ net/sunrpc/svc_xprt.c | 3 ++- 14 files changed, 56 insertions(+), 37 deletions(-) --- a/fs/ext4/extents.c~mm-introduce-memalloc_retry_wait +++ a/fs/ext4/extents.c @@ -27,8 +27,8 @@ #include <linux/slab.h> #include <linux/uaccess.h> #include <linux/fiemap.h> -#include <linux/backing-dev.h> #include <linux/iomap.h> +#include <linux/sched/mm.h> #include "ext4_jbd2.h" #include "ext4_extents.h" #include "xattr.h" @@ -4407,8 +4407,7 @@ retry: err = ext4_es_remove_extent(inode, last_block, EXT_MAX_BLOCKS - last_block); if (err == -ENOMEM) { - cond_resched(); - congestion_wait(BLK_RW_ASYNC, HZ/50); + memalloc_retry_wait(GFP_ATOMIC); goto retry; } if (err) @@ -4416,8 +4415,7 @@ retry: retry_remove_space: err = ext4_ext_remove_space(inode, last_block, EXT_MAX_BLOCKS - 1); if (err == -ENOMEM) { - cond_resched(); - congestion_wait(BLK_RW_ASYNC, HZ/50); + memalloc_retry_wait(GFP_ATOMIC); goto retry_remove_space; } return err; --- a/fs/ext4/inline.c~mm-introduce-memalloc_retry_wait +++ a/fs/ext4/inline.c @@ -7,7 +7,7 @@ #include <linux/iomap.h> #include <linux/fiemap.h> #include <linux/iversion.h> -#include <linux/backing-dev.h> +#include <linux/sched/mm.h> #include "ext4_jbd2.h" #include "ext4.h" @@ -1929,8 +1929,7 @@ int ext4_inline_data_truncate(struct ino retry: err = ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS); if (err == -ENOMEM) { - cond_resched(); - congestion_wait(BLK_RW_ASYNC, HZ/50); + memalloc_retry_wait(GFP_ATOMIC); goto retry; } if (err) --- a/fs/ext4/page-io.c~mm-introduce-memalloc_retry_wait +++ a/fs/ext4/page-io.c @@ -24,7 +24,7 @@ #include <linux/kernel.h> #include <linux/slab.h> #include <linux/mm.h> -#include <linux/backing-dev.h> +#include <linux/sched/mm.h> #include "ext4_jbd2.h" #include "xattr.h" @@ -523,12 +523,13 @@ int ext4_bio_write_page(struct ext4_io_s ret = PTR_ERR(bounce_page); if (ret == -ENOMEM && (io->io_bio || wbc->sync_mode == WB_SYNC_ALL)) { - gfp_flags = GFP_NOFS; + gfp_t new_gfp_flags = GFP_NOFS; if (io->io_bio) ext4_io_submit(io); else - gfp_flags |= __GFP_NOFAIL; - congestion_wait(BLK_RW_ASYNC, HZ/50); + new_gfp_flags |= __GFP_NOFAIL; + memalloc_retry_wait(gfp_flags); + gfp_flags = new_gfp_flags; goto retry_encrypt; } --- a/fs/f2fs/data.c~mm-introduce-memalloc_retry_wait +++ a/fs/f2fs/data.c @@ -8,9 +8,9 @@ #include <linux/fs.h> #include <linux/f2fs_fs.h> #include <linux/buffer_head.h> +#include <linux/sched/mm.h> #include <linux/mpage.h> #include <linux/writeback.h> -#include <linux/backing-dev.h> #include <linux/pagevec.h> #include <linux/blkdev.h> #include <linux/bio.h> @@ -2542,7 +2542,7 @@ retry_encrypt: /* flush pending IOs and wait for a while in the ENOMEM case */ if (PTR_ERR(fio->encrypted_page) == -ENOMEM) { f2fs_flush_merged_writes(fio->sbi); - congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT); + memalloc_retry_wait(GFP_NOFS); gfp_flags |= __GFP_NOFAIL; goto retry_encrypt; } --- a/fs/f2fs/gc.c~mm-introduce-memalloc_retry_wait +++ a/fs/f2fs/gc.c @@ -7,7 +7,6 @@ */ #include <linux/fs.h> #include <linux/module.h> -#include <linux/backing-dev.h> #include <linux/init.h> #include <linux/f2fs_fs.h> #include <linux/kthread.h> @@ -15,6 +14,7 @@ #include <linux/freezer.h> #include <linux/sched/signal.h> #include <linux/random.h> +#include <linux/sched/mm.h> #include "f2fs.h" #include "node.h" @@ -1375,8 +1375,7 @@ retry: if (err) { clear_page_private_gcing(page); if (err == -ENOMEM) { - congestion_wait(BLK_RW_ASYNC, - DEFAULT_IO_TIMEOUT); + memalloc_retry_wait(GFP_NOFS); goto retry; } if (is_dirty) --- a/fs/f2fs/inode.c~mm-introduce-memalloc_retry_wait +++ a/fs/f2fs/inode.c @@ -8,8 +8,8 @@ #include <linux/fs.h> #include <linux/f2fs_fs.h> #include <linux/buffer_head.h> -#include <linux/backing-dev.h> #include <linux/writeback.h> +#include <linux/sched/mm.h> #include "f2fs.h" #include "node.h" @@ -562,7 +562,7 @@ retry: inode = f2fs_iget(sb, ino); if (IS_ERR(inode)) { if (PTR_ERR(inode) == -ENOMEM) { - congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT); + memalloc_retry_wait(GFP_NOFS); goto retry; } } --- a/fs/f2fs/node.c~mm-introduce-memalloc_retry_wait +++ a/fs/f2fs/node.c @@ -8,7 +8,7 @@ #include <linux/fs.h> #include <linux/f2fs_fs.h> #include <linux/mpage.h> -#include <linux/backing-dev.h> +#include <linux/sched/mm.h> #include <linux/blkdev.h> #include <linux/pagevec.h> #include <linux/swap.h> @@ -2750,7 +2750,7 @@ int f2fs_recover_inode_page(struct f2fs_ retry: ipage = f2fs_grab_cache_page(NODE_MAPPING(sbi), ino, false); if (!ipage) { - congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT); + memalloc_retry_wait(GFP_NOFS); goto retry; } --- a/fs/f2fs/recovery.c~mm-introduce-memalloc_retry_wait +++ a/fs/f2fs/recovery.c @@ -8,6 +8,7 @@ #include <asm/unaligned.h> #include <linux/fs.h> #include <linux/f2fs_fs.h> +#include <linux/sched/mm.h> #include "f2fs.h" #include "node.h" #include "segment.h" @@ -587,7 +588,7 @@ retry_dn: err = f2fs_get_dnode_of_data(&dn, start, ALLOC_NODE); if (err) { if (err == -ENOMEM) { - congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT); + memalloc_retry_wait(GFP_NOFS); goto retry_dn; } goto out; @@ -670,8 +671,7 @@ retry_prev: err = check_index_in_prev_nodes(sbi, dest, &dn); if (err) { if (err == -ENOMEM) { - congestion_wait(BLK_RW_ASYNC, - DEFAULT_IO_TIMEOUT); + memalloc_retry_wait(GFP_NOFS); goto retry_prev; } goto err; --- a/fs/f2fs/segment.c~mm-introduce-memalloc_retry_wait +++ a/fs/f2fs/segment.c @@ -9,6 +9,7 @@ #include <linux/f2fs_fs.h> #include <linux/bio.h> #include <linux/blkdev.h> +#include <linux/sched/mm.h> #include <linux/prefetch.h> #include <linux/kthread.h> #include <linux/swap.h> @@ -245,9 +246,7 @@ retry: LOOKUP_NODE); if (err) { if (err == -ENOMEM) { - congestion_wait(BLK_RW_ASYNC, - DEFAULT_IO_TIMEOUT); - cond_resched(); + memalloc_retry_wait(GFP_NOFS); goto retry; } err = -EAGAIN; @@ -424,9 +423,7 @@ retry: err = f2fs_do_write_data_page(&fio); if (err) { if (err == -ENOMEM) { - congestion_wait(BLK_RW_ASYNC, - DEFAULT_IO_TIMEOUT); - cond_resched(); + memalloc_retry_wait(GFP_NOFS); goto retry; } unlock_page(page); --- a/fs/f2fs/super.c~mm-introduce-memalloc_retry_wait +++ a/fs/f2fs/super.c @@ -8,9 +8,9 @@ #include <linux/module.h> #include <linux/init.h> #include <linux/fs.h> +#include <linux/sched/mm.h> #include <linux/statfs.h> #include <linux/buffer_head.h> -#include <linux/backing-dev.h> #include <linux/kthread.h> #include <linux/parser.h> #include <linux/mount.h> @@ -2415,8 +2415,7 @@ repeat: page = read_cache_page_gfp(mapping, blkidx, GFP_NOFS); if (IS_ERR(page)) { if (PTR_ERR(page) == -ENOMEM) { - congestion_wait(BLK_RW_ASYNC, - DEFAULT_IO_TIMEOUT); + memalloc_retry_wait(GFP_NOFS); goto repeat; } set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR); --- a/fs/xfs/kmem.c~mm-introduce-memalloc_retry_wait +++ a/fs/xfs/kmem.c @@ -4,7 +4,6 @@ * All Rights Reserved. */ #include "xfs.h" -#include <linux/backing-dev.h> #include "xfs_message.h" #include "xfs_trace.h" @@ -26,6 +25,6 @@ kmem_alloc(size_t size, xfs_km_flags_t f "%s(%u) possible memory allocation deadlock size %u in %s (mode:0x%x)", current->comm, current->pid, (unsigned int)size, __func__, lflags); - congestion_wait(BLK_RW_ASYNC, HZ/50); + memalloc_retry_wait(lflags); } while (1); } --- a/fs/xfs/xfs_buf.c~mm-introduce-memalloc_retry_wait +++ a/fs/xfs/xfs_buf.c @@ -394,7 +394,7 @@ xfs_buf_alloc_pages( } XFS_STATS_INC(bp->b_mount, xb_page_retries); - congestion_wait(BLK_RW_ASYNC, HZ / 50); + memalloc_retry_wait(gfp_mask); } return 0; } --- a/include/linux/sched/mm.h~mm-introduce-memalloc_retry_wait +++ a/include/linux/sched/mm.h @@ -214,6 +214,32 @@ static inline void fs_reclaim_acquire(gf static inline void fs_reclaim_release(gfp_t gfp_mask) { } #endif +/* Any memory-allocation retry loop should use + * memalloc_retry_wait(), and pass the flags for the most + * constrained allocation attempt that might have failed. + * This provides useful documentation of where loops are, + * and a central place to fine tune the waiting as the MM + * implementation changes. + */ +static inline void memalloc_retry_wait(gfp_t gfp_flags) +{ + /* We use io_schedule_timeout because waiting for memory + * typically included waiting for dirty pages to be + * written out, which requires IO. + */ + __set_current_state(TASK_UNINTERRUPTIBLE); + gfp_flags = current_gfp_context(gfp_flags); + if (gfpflags_allow_blocking(gfp_flags) && + !(gfp_flags & __GFP_NORETRY)) + /* Probably waited already, no need for much more */ + io_schedule_timeout(1); + else + /* Probably didn't wait, and has now released a lock, + * so now is a good time to wait + */ + io_schedule_timeout(HZ/50); +} + /** * might_alloc - Mark possible allocation sites * @gfp_mask: gfp_t flags that would be used to allocate --- a/net/sunrpc/svc_xprt.c~mm-introduce-memalloc_retry_wait +++ a/net/sunrpc/svc_xprt.c @@ -6,6 +6,7 @@ */ #include <linux/sched.h> +#include <linux/sched/mm.h> #include <linux/errno.h> #include <linux/freezer.h> #include <linux/kthread.h> @@ -688,7 +689,7 @@ static int svc_alloc_arg(struct svc_rqst return -EINTR; } trace_svc_alloc_arg_err(pages); - schedule_timeout(msecs_to_jiffies(500)); + memalloc_retry_wait(GFP_KERNEL); } rqstp->rq_page_end = &rqstp->rq_pages[pages]; rqstp->rq_pages[pages] = NULL; /* this might be seen in nfsd_splice_actor() */ _
