[PATCH] Revert "readahead: properly shorten readahead when falling back to do_page_cache_ra()"
This reverts commit 7c877586da3178974a8a94577b6045a48377ff25.
Anders and Philippe have reported that recent kernels occasionally hang when used with NFS in readahead code. The problem has been bisected to 7c877586da3 ("readahead: properly shorten readahead when falling back to do_page_cache_ra()"). The cause of the problem is that ra->size can be shrunk by read_pages() call and subsequently we end up calling do_page_cache_ra() with negative (read huge positive) number of pages. Let's revert 7c877586da3 for now until we can find a proper way how the logic in read_pages() and page_cache_ra_order() can coexist. This can lead to reduced readahead throughput due to readahead window confusion but that's better than outright hangs.
Reported-by: Anders Blomdell anders.blomdell@gmail.com Reported-by: Philippe Troin phil@fifi.org CC: stable@vger.kernel.org Signed-off-by: Jan Kara jack@suse.cz --- mm/readahead.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/mm/readahead.c b/mm/readahead.c index 8f1cf599b572..ea650b8b02fb 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -458,8 +458,7 @@ void page_cache_ra_order(struct readahead_control *ractl, struct file_ra_state *ra, unsigned int new_order) { struct address_space *mapping = ractl->mapping; - pgoff_t start = readahead_index(ractl); - pgoff_t index = start; + pgoff_t index = readahead_index(ractl); unsigned int min_order = mapping_min_folio_order(mapping); pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT; pgoff_t mark = index + ra->size - ra->async_size; @@ -522,7 +521,7 @@ void page_cache_ra_order(struct readahead_control *ractl, if (!err) return; fallback: - do_page_cache_ra(ractl, ra->size - (index - start), ra->async_size); + do_page_cache_ra(ractl, ra->size, ra->async_size); }
static unsigned long ractl_max_pages(struct readahead_control *ractl,
On Tue, 2024-11-26 at 15:52 +0100, Jan Kara wrote:
This reverts commit 7c877586da3178974a8a94577b6045a48377ff25.
Anders and Philippe have reported that recent kernels occasionally hang when used with NFS in readahead code. The problem has been bisected to 7c877586da3 ("readahead: properly shorten readahead when falling back to do_page_cache_ra()"). The cause of the problem is that ra->size can be shrunk by read_pages() call and subsequently we end up calling do_page_cache_ra() with negative (read huge positive) number of pages. Let's revert 7c877586da3 for now until we can find a proper way how the logic in read_pages() and page_cache_ra_order() can coexist. This can lead to reduced readahead throughput due to readahead window confusion but that's better than outright hangs.
Reported-by: Anders Blomdell anders.blomdell@gmail.com Reported-by: Philippe Troin phil@fifi.org CC: stable@vger.kernel.org Signed-off-by: Jan Kara jack@suse.cz
mm/readahead.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/mm/readahead.c b/mm/readahead.c index 8f1cf599b572..ea650b8b02fb 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -458,8 +458,7 @@ void page_cache_ra_order(struct readahead_control *ractl, struct file_ra_state *ra, unsigned int new_order) { struct address_space *mapping = ractl->mapping;
- pgoff_t start = readahead_index(ractl);
- pgoff_t index = start;
- pgoff_t index = readahead_index(ractl);
unsigned int min_order = mapping_min_folio_order(mapping); pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT; pgoff_t mark = index + ra->size - ra->async_size; @@ -522,7 +521,7 @@ void page_cache_ra_order(struct readahead_control *ractl, if (!err) return; fallback:
- do_page_cache_ra(ractl, ra->size - (index - start), ra->async_size);
- do_page_cache_ra(ractl, ra->size, ra->async_size);
} static unsigned long ractl_max_pages(struct readahead_control *ractl,
You can add a Tested-by: Philippe Troin phil@fifi.org tag as I did experiment and validate the fix with that revert on top of 6.11.10.
Phil.
linux-stable-mirror@lists.linaro.org
-
Jan Kara -
Philippe Troin