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authorJan Kara <jack@suse.cz>2020-04-01 21:04:40 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-02 09:35:26 -0700
commit5c72feee3e45b40a3c96c7145ec422899d0e8964 (patch)
tree91843a458e7055013b79897a9de59f6bab44e02e /mm/filemap.c
parent5f2d5026be67691af26327ab722db4dacaacf399 (diff)
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mm/filemap.c: don't bother dropping mmap_sem for zero size readahead
When handling a page fault, we drop mmap_sem to start async readahead so that we don't block on IO submission with mmap_sem held. However there's no point to drop mmap_sem in case readahead is disabled. Handle that case to avoid pointless dropping of mmap_sem and retrying the fault. This was actually reported to block mlockall(MCL_CURRENT) indefinitely. Fixes: 6b4c9f446981 ("filemap: drop the mmap_sem for all blocking operations") Reported-by: Minchan Kim <minchan@kernel.org> Reported-by: Robert Stupp <snazy@gmx.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Link: http://lkml.kernel.org/r/20200212101356.30759-1-jack@suse.cz Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap.c')
-rw-r--r--mm/filemap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 1784478270e1..5bffaa2176cd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2416,7 +2416,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
pgoff_t offset = vmf->pgoff;
/* If we don't want any read-ahead, don't bother */
- if (vmf->vma->vm_flags & VM_RAND_READ)
+ if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
return fpin;
if (ra->mmap_miss > 0)
ra->mmap_miss--;