On Mon, May 16, 2022 at 6:51 PM Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote: > > Implement readahead callback for squashfs. It will read datablocks > which cover pages in readahead request. For a few cases it will > not mark page as uptodate, including: > - file end is 0. > - zero filled blocks. > - current batch of pages isn't in the same datablock or not enough in a > datablock. > Otherwise pages will be marked as uptodate. The unhandled pages will be > updated by readpage later. > Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> > --- > Note that this patch was not formally sent to the list before. It's > attached to email thread for discussion as it's still under development. > > - v1: > The patch outline was suggested by Matthew. It went through a few > reviews by Matthew offline. > > - v2: > https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m442435c149d411c5c9d8019cff5915419b04bf10 > This is a resend of v1. > > - v3: > https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m55a709e6ba5ec59fe95323a67a7f3d6b1953e470 > Fix page actor size to avoid a crash from squashfs_decompress(). > Suggested by Phillip Lougher[1] > [1] https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m687f82debb7667ff31982a05aef3eba081eb5039 > > - v4: > https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#mf93267690ec2e841dade6a494fe72c84b61328d9 > Fix to free page after used. Suggested by Xiongwei Song[2] > Refactor the skip page logic to possible improve the performance. > Suggested by Phillip Lougher[3] > [2] https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m0e7b33d167b1ef0eb39b9f41c32ed3f80dfced18 > [3] https://lore.kernel.org/linux-mm/Yn5Yij9pRPCzDozt@xxxxxxxxxxxxxxxxxxxx/t/#m1e0a8f8e4a98d79d14c81b66e197b6dc0a3b77a1 > --- > fs/squashfs/file.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 77 insertions(+) > > diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c > index a8e495d8eb86..91dfec792f4c 100644 > --- a/fs/squashfs/file.c > +++ b/fs/squashfs/file.c > @@ -39,6 +39,7 @@ > #include "squashfs_fs_sb.h" > #include "squashfs_fs_i.h" > #include "squashfs.h" > +#include "page_actor.h" > > /* > * Locate cache slot in range [offset, index] for specified inode. If > @@ -495,7 +496,83 @@ static int squashfs_read_folio(struct file *file, struct folio *folio) > return 0; > } > > +static void squashfs_readahead(struct readahead_control *ractl) > +{ > + struct inode *inode = ractl->mapping->host; > + struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; > + size_t mask = (1UL << msblk->block_log) - 1; > + size_t shift = msblk->block_log - PAGE_SHIFT; > + loff_t req_end = readahead_pos(ractl) + readahead_length(ractl); > + loff_t start = readahead_pos(ractl) &~ mask; > + size_t len = readahead_length(ractl) + readahead_pos(ractl) - start; > + struct squashfs_page_actor *actor; > + unsigned int nr_pages = 0; > + struct page **pages; > + u64 block = 0; > + int bsize, res, i, index; > + int file_end = i_size_read(inode) >> msblk->block_log; > + unsigned int max_pages = 1UL << shift; > + > + readahead_expand(ractl, start, (len | mask) + 1); > + > + if (readahead_pos(ractl) + readahead_length(ractl) < req_end || > + file_end == 0) > + return; > + > + pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL); > + if (!pages) > + return; > + > + actor = squashfs_page_actor_init_special(pages, max_pages, 0); > + if (!actor) > + goto out; > + > + for (;;) { > + nr_pages = __readahead_batch(ractl, pages, max_pages); > + if (!nr_pages) > + break; > + > + if (readahead_pos(ractl) >= i_size_read(inode) || > + nr_pages < max_pages) > + goto skip_pages; > + > + index = pages[0]->index >> shift; > + if ((pages[nr_pages - 1]->index >> shift) != index) > + goto skip_pages; > + > + bsize = read_blocklist(inode, index, &block); > + if (bsize == 0) > + goto skip_pages; > + > + res = squashfs_read_data(inode->i_sb, block, bsize, NULL, > + actor); > + > + if (res >= 0) > + for (i = 0; i < nr_pages; i++) > + SetPageUptodate(pages[i]); > + > + for (i = 0; i < nr_pages; i++) { > + unlock_page(pages[i]); > + put_page(pages[i]); > + } > + } > + > + kfree(actor); > + kfree(pages); > + return; > + > +skip_pages: > + for (i = 0; i < nr_pages; i++) { > + unlock_page(pages[i]); > + put_page(pages[i]); > + } > + > + kfree(actor); > +out: > + kfree(pages); > +} > > const struct address_space_operations squashfs_aops = { > .read_folio = squashfs_read_folio > + .readahead = squashfs_readahead > }; > -- > 2.36.0.550.gb090851708-goog >
