Messages in this thread Patch in this message | | | From | Minchan Kim <> | Subject | [PATCH 1/3] mm: Don't bother dropping mmap_sem for zero size readahead | Date | Wed, 12 Feb 2020 14:16:12 -0800 |
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From: Jan Kara <jack@suse.cz>
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> Reviewed-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
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--; -- 2.25.0.225.g125e21ebc7-goog
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