| Message ID | 163712329077.13692.12796971766360881401@noble.neil.brown.name (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | MM: introduce memalloc_retry_wait() | expand |
On Wed, Nov 17, 2021 at 03:28:10PM +1100, NeilBrown wrote: > > Various places in the kernel - largely in filesystems - respond to a > memory allocation failure by looping around and re-trying. ..... > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index aca874d33fe6..f2f2a5b28808 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -214,6 +214,27 @@ static inline void fs_reclaim_acquire(gfp_t gfp_mask) { } > 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) > +{ > + gfp_flags = current_gfp_context(gfp_flags); > + if ((gfp_flags & __GFP_DIRECT_RECLAIM) && > + !(gfp_flags & __GFP_NORETRY)) > + /* Probably waited already, no need for much more */ > + schedule_timeout_uninterruptible(1); > + else > + /* Probably didn't wait, and has now released a lock, > + * so now is a good time to wait > + */ > + schedule_timeout_uninterruptible(HZ/50); > +} The existing congestion_wait() calls io_schedule_timeout() under TASK_UNINTERRUPTIBLE conditions. Does changing all these calls just to a plain schedule_timeout_uninterruptible() make any difference to behaviour? At least process accounting will appear different (uninterruptible sleep instead of IO wait), and I suspect that the block plug flushing in io_schedule() might be a good idea to retain for all the filesystems that call this function from IO-related routines. Cheers, Dave.
Hi NeilBrown,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on jaegeuk-f2fs/dev-test]
[also build test ERROR on v5.16-rc1 next-20211118]
[cannot apply to tytso-ext4/dev xfs-linux/for-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/NeilBrown/MM-introduce-memalloc_retry_wait/20211117-122932
base: https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git dev-test
config: riscv-randconfig-r004-20211118 (attached as .config)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install riscv cross compiling tool for clang build
# apt-get install binutils-riscv64-linux-gnu
# https://github.com/0day-ci/linux/commit/1da355dc212c5f6ade3a21d4a5b1cfaf6b48ff0f
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review NeilBrown/MM-introduce-memalloc_retry_wait/20211117-122932
git checkout 1da355dc212c5f6ade3a21d4a5b1cfaf6b48ff0f
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=riscv
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
>> fs/f2fs/super.c:2417:5: error: implicit declaration of function 'memalloc_retry_wait' [-Werror,-Wimplicit-function-declaration]
memalloc_retry_wait(GFP_NOFS);
^
1 error generated.
vim +/memalloc_retry_wait +2417 fs/f2fs/super.c
2389
2390 #ifdef CONFIG_QUOTA
2391 /* Read data from quotafile */
2392 static ssize_t f2fs_quota_read(struct super_block *sb, int type, char *data,
2393 size_t len, loff_t off)
2394 {
2395 struct inode *inode = sb_dqopt(sb)->files[type];
2396 struct address_space *mapping = inode->i_mapping;
2397 block_t blkidx = F2FS_BYTES_TO_BLK(off);
2398 int offset = off & (sb->s_blocksize - 1);
2399 int tocopy;
2400 size_t toread;
2401 loff_t i_size = i_size_read(inode);
2402 struct page *page;
2403 char *kaddr;
2404
2405 if (off > i_size)
2406 return 0;
2407
2408 if (off + len > i_size)
2409 len = i_size - off;
2410 toread = len;
2411 while (toread > 0) {
2412 tocopy = min_t(unsigned long, sb->s_blocksize - offset, toread);
2413 repeat:
2414 page = read_cache_page_gfp(mapping, blkidx, GFP_NOFS);
2415 if (IS_ERR(page)) {
2416 if (PTR_ERR(page) == -ENOMEM) {
> 2417 memalloc_retry_wait(GFP_NOFS);
2418 goto repeat;
2419 }
2420 set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
2421 return PTR_ERR(page);
2422 }
2423
2424 lock_page(page);
2425
2426 if (unlikely(page->mapping != mapping)) {
2427 f2fs_put_page(page, 1);
2428 goto repeat;
2429 }
2430 if (unlikely(!PageUptodate(page))) {
2431 f2fs_put_page(page, 1);
2432 set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
2433 return -EIO;
2434 }
2435
2436 kaddr = kmap_atomic(page);
2437 memcpy(data, kaddr + offset, tocopy);
2438 kunmap_atomic(kaddr);
2439 f2fs_put_page(page, 1);
2440
2441 offset = 0;
2442 toread -= tocopy;
2443 data += tocopy;
2444 blkidx++;
2445 }
2446 return len;
2447 }
2448
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Hi NeilBrown,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on jaegeuk-f2fs/dev-test]
[also build test ERROR on v5.16-rc1 next-20211118]
[cannot apply to xfs-linux/for-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/NeilBrown/MM-introduce-memalloc_retry_wait/20211117-122932
base: https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git dev-test
config: arc-randconfig-r043-20211117 (attached as .config)
compiler: arceb-elf-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/1da355dc212c5f6ade3a21d4a5b1cfaf6b48ff0f
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review NeilBrown/MM-introduce-memalloc_retry_wait/20211117-122932
git checkout 1da355dc212c5f6ade3a21d4a5b1cfaf6b48ff0f
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=arc
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
fs/f2fs/super.c: In function 'f2fs_quota_read':
>> fs/f2fs/super.c:2417:33: error: implicit declaration of function 'memalloc_retry_wait' [-Werror=implicit-function-declaration]
2417 | memalloc_retry_wait(GFP_NOFS);
| ^~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
vim +/memalloc_retry_wait +2417 fs/f2fs/super.c
2389
2390 #ifdef CONFIG_QUOTA
2391 /* Read data from quotafile */
2392 static ssize_t f2fs_quota_read(struct super_block *sb, int type, char *data,
2393 size_t len, loff_t off)
2394 {
2395 struct inode *inode = sb_dqopt(sb)->files[type];
2396 struct address_space *mapping = inode->i_mapping;
2397 block_t blkidx = F2FS_BYTES_TO_BLK(off);
2398 int offset = off & (sb->s_blocksize - 1);
2399 int tocopy;
2400 size_t toread;
2401 loff_t i_size = i_size_read(inode);
2402 struct page *page;
2403 char *kaddr;
2404
2405 if (off > i_size)
2406 return 0;
2407
2408 if (off + len > i_size)
2409 len = i_size - off;
2410 toread = len;
2411 while (toread > 0) {
2412 tocopy = min_t(unsigned long, sb->s_blocksize - offset, toread);
2413 repeat:
2414 page = read_cache_page_gfp(mapping, blkidx, GFP_NOFS);
2415 if (IS_ERR(page)) {
2416 if (PTR_ERR(page) == -ENOMEM) {
> 2417 memalloc_retry_wait(GFP_NOFS);
2418 goto repeat;
2419 }
2420 set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
2421 return PTR_ERR(page);
2422 }
2423
2424 lock_page(page);
2425
2426 if (unlikely(page->mapping != mapping)) {
2427 f2fs_put_page(page, 1);
2428 goto repeat;
2429 }
2430 if (unlikely(!PageUptodate(page))) {
2431 f2fs_put_page(page, 1);
2432 set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
2433 return -EIO;
2434 }
2435
2436 kaddr = kmap_atomic(page);
2437 memcpy(data, kaddr + offset, tocopy);
2438 kunmap_atomic(kaddr);
2439 f2fs_put_page(page, 1);
2440
2441 offset = 0;
2442 toread -= tocopy;
2443 data += tocopy;
2444 blkidx++;
2445 }
2446 return len;
2447 }
2448
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 0ecf819bf189..5582fba36b44 100644 --- a/fs/ext4/extents.c +++ b/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 @@ int ext4_ext_truncate(handle_t *handle, struct inode *inode) 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 @@ int ext4_ext_truncate(handle_t *handle, struct inode *inode) 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; diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 39a1ab129fdc..635bcf68a67e 100644 --- a/fs/ext4/inline.c +++ b/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 inode *inode, int *has_inline) 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) diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index 9cb261714991..1d370364230e 100644 --- a/fs/ext4/page-io.c +++ b/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_submit *io, 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; } diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 9f754aaef558..48b80e7ec35e 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -10,7 +10,6 @@ #include <linux/buffer_head.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 +2541,7 @@ int f2fs_encrypt_one_page(struct f2fs_io_info *fio) /* 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; } diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c index a946ce0ead34..374bbb5294d9 100644 --- a/fs/f2fs/gc.c +++ b/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 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type, 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) diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c index 0f8b2df3e1e0..4c11254a07d4 100644 --- a/fs/f2fs/inode.c +++ b/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 @@ struct inode *f2fs_iget_retry(struct super_block *sb, unsigned long ino) 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; } } diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index 556fcd8457f3..f8646c29e00b 100644 --- a/fs/f2fs/node.c +++ b/fs/f2fs/node.c @@ -8,7 +8,6 @@ #include <linux/fs.h> #include <linux/f2fs_fs.h> #include <linux/mpage.h> -#include <linux/backing-dev.h> #include <linux/blkdev.h> #include <linux/pagevec.h> #include <linux/swap.h> @@ -2750,7 +2749,7 @@ int f2fs_recover_inode_page(struct f2fs_sb_info *sbi, struct page *page) 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; } diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c index 6a1b4668d933..d1664a0567ef 100644 --- a/fs/f2fs/recovery.c +++ b/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 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode, 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 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode, 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; diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index df9ed75f0b7a..6140eada8607 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -245,9 +245,7 @@ static int __revoke_inmem_pages(struct inode *inode, 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 +422,7 @@ static int __f2fs_commit_inmem_pages(struct inode *inode) 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); diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 040b6d02e1d8..be9006d6213f 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -10,7 +10,6 @@ #include <linux/fs.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 +2414,7 @@ static ssize_t f2fs_quota_read(struct super_block *sb, int type, char *data, 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); diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c index 6f49bf39183c..c557a030acfe 100644 --- a/fs/xfs/kmem.c +++ b/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 flags) "%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); } diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index 631c5a61d89b..6c45e3fa56f4 100644 --- a/fs/xfs/xfs_buf.c +++ b/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; } diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index aca874d33fe6..f2f2a5b28808 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -214,6 +214,27 @@ static inline void fs_reclaim_acquire(gfp_t gfp_mask) { } 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) +{ + gfp_flags = current_gfp_context(gfp_flags); + if ((gfp_flags & __GFP_DIRECT_RECLAIM) && + !(gfp_flags & __GFP_NORETRY)) + /* Probably waited already, no need for much more */ + schedule_timeout_uninterruptible(1); + else + /* Probably didn't wait, and has now released a lock, + * so now is a good time to wait + */ + schedule_timeout_uninterruptible(HZ/50); +} + /** * might_alloc - Mark possible allocation sites * @gfp_mask: gfp_t flags that would be used to allocate diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 1e99ba1b9d72..f9584e8e8324 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -688,7 +688,7 @@ static int svc_alloc_arg(struct svc_rqst *rqstp) 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() */
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 the __GFP_DIRECT_RECLAIM and __GFP_NORETRY flags. If DIRECT_RECLAIM is set 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. 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. Signed-off-by: NeilBrown <neilb@suse.de> --- I could split this up by filesystems if people prefer that, but they we would have to wait for the -mm patch to land before they could be applied. What do people think? Can Andrew just collected acked-bys? Thanks, NeilBrown fs/ext4/extents.c | 8 +++----- fs/ext4/inline.c | 5 ++--- fs/ext4/page-io.c | 9 +++++---- fs/f2fs/data.c | 3 +-- fs/f2fs/gc.c | 5 ++--- fs/f2fs/inode.c | 4 ++-- fs/f2fs/node.c | 3 +-- fs/f2fs/recovery.c | 6 +++--- fs/f2fs/segment.c | 8 ++------ fs/f2fs/super.c | 4 +--- fs/xfs/kmem.c | 3 +-- fs/xfs/xfs_buf.c | 2 +- include/linux/sched/mm.h | 21 +++++++++++++++++++++ net/sunrpc/svc_xprt.c | 2 +- 14 files changed, 46 insertions(+), 37 deletions(-)