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Revert "mm: limit filemap_fault readahead to VMA boundaries"

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This reverts commit 7b32f64bc5.

This patch caused a significant performance regression, so revert it, and
we can determine whether the approach is sensible or not moving forwards,
and if so how to avoid this.

There was a merge conflict with commit de97ae6222 ("mm/readahead: no
PG_readahead on EOF"), care was taken to ensure that the revert retained
the behaviour of this patch and cleanly reverts commit 7b32f64bc5 ("mm:
limit filemap_fault readahead to VMA boundaries") only.

Link: https://lore.kernel.org/20260619112852.104213-1-ljs@kernel.org
Fixes: 7b32f64bc5 ("mm: limit filemap_fault readahead to VMA boundaries")
Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202606181547.617a6967-lkp@intel.com
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes 2026-06-19 12:28:51 +01:00 committed by Andrew Morton
parent 44238b122a
commit 13a1e1a618
3 changed files with 1 additions and 11 deletions
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2
include/linux/pagemap.h
View File

@ -1348,7 +1348,6 @@ struct readahead_control {
struct file_ra_state *ra;
/* private: use the readahead_* accessors instead */
pgoff_t _index;
pgoff_t _max_index; /* limit readahead to _max_index, inclusive */
unsigned int _nr_pages;
unsigned int _batch_count;
bool dropbehind;
@ -1362,7 +1361,6 @@ struct readahead_control {
.mapping = m, \
.ra = r, \
._index = i, \
._max_index = ULONG_MAX, \
}
#define VM_READAHEAD_PAGES (SZ_128K / PAGE_SIZE)

4
mm/filemap.c
View File

@ -3312,8 +3312,6 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
unsigned int thp_order = 0;
unsigned short mmap_miss;
ractl._max_index = vmf->vma->vm_pgoff + vma_pages(vmf->vma) - 1;
/* Use the readahead code, even if readahead is disabled */
if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && (vm_flags & VM_HUGEPAGE)) {
/*
@ -3409,7 +3407,6 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
* mmap read-around
*/
ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
ra->start = max(ra->start, vmf->vma->vm_pgoff);
ra->size = ra->ra_pages;
ra->async_size = ra->ra_pages / 4;
ra->order = 0;
@ -3457,7 +3454,6 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
}
if (folio_test_readahead(folio)) {
ractl._max_index = vmf->vma->vm_pgoff + vma_pages(vmf->vma) - 1;
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
page_cache_async_ra(&ractl, folio, ra->ra_pages);
}

6
mm/readahead.c
View File

@ -335,8 +335,6 @@ static void do_page_cache_ra(struct readahead_control *ractl,
return;
end_index = (isize - 1) >> PAGE_SHIFT;
if (end_index > ractl->_max_index)
end_index = ractl->_max_index;
if (index > end_index)
return;
/* Don't read past the page containing the last byte of the file */
@ -487,7 +485,7 @@ void page_cache_ra_order(struct readahead_control *ractl,
pgoff_t start = readahead_index(ractl);
pgoff_t index = start;
unsigned int min_order = mapping_min_folio_order(mapping);
pgoff_t limit;
pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT;
pgoff_t mark;
unsigned int nofs;
int err = 0;
@ -500,8 +498,6 @@ void page_cache_ra_order(struct readahead_control *ractl,
goto fallback;
}
limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT;
limit = min(limit, ractl->_max_index);
if (limit > index + ra->size - 1) {
limit = index + ra->size - 1;
mark = index + ra->size - ra->async_size;