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author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2021-02-26 02:15:48 +0100 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-02-26 18:40:59 +0100 |
commit | 41139aa4c3a31ee7e072fc63353c74035aade2ff (patch) | |
tree | f41cd1085eb89b74a1c31f79c0641dd2cf7a5631 /mm | |
parent | mm/filemap: add helper for finding pages (diff) | |
download | linux-41139aa4c3a31ee7e072fc63353c74035aade2ff.tar.xz linux-41139aa4c3a31ee7e072fc63353c74035aade2ff.zip |
mm/filemap: add mapping_seek_hole_data
Rewrite shmem_seek_hole_data() and move it to filemap.c.
[willy@infradead.org: don't put an xa_is_value() page]
Link: https://lkml.kernel.org/r/20201124041507.28996-4-willy@infradead.org
Link: https://lkml.kernel.org/r/20201112212641.27837-8-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/filemap.c | 76 | ||||
-rw-r--r-- | mm/shmem.c | 74 |
2 files changed, 80 insertions, 70 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 21443850aeae..eff3006be12a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2553,6 +2553,82 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) } EXPORT_SYMBOL(generic_file_read_iter); +static inline bool page_seek_match(struct page *page, bool seek_data) +{ + if (xa_is_value(page) || PageUptodate(page)) + return seek_data; + return !seek_data; +} + +static inline +unsigned int seek_page_size(struct xa_state *xas, struct page *page) +{ + if (xa_is_value(page)) + return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index); + return thp_size(page); +} + +/** + * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache. + * @mapping: Address space to search. + * @start: First byte to consider. + * @end: Limit of search (exclusive). + * @whence: Either SEEK_HOLE or SEEK_DATA. + * + * If the page cache knows which blocks contain holes and which blocks + * contain data, your filesystem can use this function to implement + * SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are + * entirely memory-based such as tmpfs, and filesystems which support + * unwritten extents. + * + * Return: The requested offset on successs, or -ENXIO if @whence specifies + * SEEK_DATA and there is no data after @start. There is an implicit hole + * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start + * and @end contain data. + */ +loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start, + loff_t end, int whence) +{ + XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT); + pgoff_t max = (end - 1) / PAGE_SIZE; + bool seek_data = (whence == SEEK_DATA); + struct page *page; + + if (end <= start) + return -ENXIO; + + rcu_read_lock(); + while ((page = find_get_entry(&xas, max, XA_PRESENT))) { + loff_t pos = xas.xa_index * PAGE_SIZE; + + if (start < pos) { + if (!seek_data) + goto unlock; + start = pos; + } + + if (page_seek_match(page, seek_data)) + goto unlock; + start = pos + seek_page_size(&xas, page); + if (!xa_is_value(page)) + put_page(page); + } + rcu_read_unlock(); + + if (seek_data) + return -ENXIO; + goto out; + +unlock: + rcu_read_unlock(); + if (!xa_is_value(page)) + put_page(page); +out: + if (start > end) + return end; + return start; +} + #ifdef CONFIG_MMU #define MMAP_LOTSAMISS (100) /* diff --git a/mm/shmem.c b/mm/shmem.c index bd5bb78128af..deb22e128435 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2668,86 +2668,20 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) return retval ? retval : error; } -/* - * llseek SEEK_DATA or SEEK_HOLE through the page cache. - */ -static pgoff_t shmem_seek_hole_data(struct address_space *mapping, - pgoff_t index, pgoff_t end, int whence) -{ - struct page *page; - struct pagevec pvec; - pgoff_t indices[PAGEVEC_SIZE]; - bool done = false; - int i; - - pagevec_init(&pvec); - pvec.nr = 1; /* start small: we may be there already */ - while (!done) { - pvec.nr = find_get_entries(mapping, index, - pvec.nr, pvec.pages, indices); - if (!pvec.nr) { - if (whence == SEEK_DATA) - index = end; - break; - } - for (i = 0; i < pvec.nr; i++, index++) { - if (index < indices[i]) { - if (whence == SEEK_HOLE) { - done = true; - break; - } - index = indices[i]; - } - page = pvec.pages[i]; - if (page && !xa_is_value(page)) { - if (!PageUptodate(page)) - page = NULL; - } - if (index >= end || - (page && whence == SEEK_DATA) || - (!page && whence == SEEK_HOLE)) { - done = true; - break; - } - } - pagevec_remove_exceptionals(&pvec); - pagevec_release(&pvec); - pvec.nr = PAGEVEC_SIZE; - cond_resched(); - } - return index; -} - static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence) { struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; - pgoff_t start, end; - loff_t new_offset; if (whence != SEEK_DATA && whence != SEEK_HOLE) return generic_file_llseek_size(file, offset, whence, MAX_LFS_FILESIZE, i_size_read(inode)); + if (offset < 0) + return -ENXIO; + inode_lock(inode); /* We're holding i_mutex so we can access i_size directly */ - - if (offset < 0 || offset >= inode->i_size) - offset = -ENXIO; - else { - start = offset >> PAGE_SHIFT; - end = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; - new_offset = shmem_seek_hole_data(mapping, start, end, whence); - new_offset <<= PAGE_SHIFT; - if (new_offset > offset) { - if (new_offset < inode->i_size) - offset = new_offset; - else if (whence == SEEK_DATA) - offset = -ENXIO; - else - offset = inode->i_size; - } - } - + offset = mapping_seek_hole_data(mapping, offset, inode->i_size, whence); if (offset >= 0) offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE); inode_unlock(inode); |