diff options
| -rw-r--r-- | mm/shmem.c | 58 |
1 files changed, 56 insertions, 2 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 793dcd1bac8b..191663a8def3 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -84,6 +84,18 @@ struct shmem_xattr { char value[0]; }; +/* + * shmem_fallocate and shmem_writepage communicate via inode->i_private + * (with i_mutex making sure that it has only one user at a time): + * we would prefer not to enlarge the shmem inode just for that. + */ +struct shmem_falloc { + pgoff_t start; /* start of range currently being fallocated */ + pgoff_t next; /* the next page offset to be fallocated */ + pgoff_t nr_falloced; /* how many new pages have been fallocated */ + pgoff_t nr_unswapped; /* how often writepage refused to swap out */ +}; + /* Flag allocation requirements to shmem_getpage */ enum sgp_type { SGP_READ, /* don't exceed i_size, don't allocate page */ @@ -791,8 +803,28 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC * value into swapfile.c, the only way we can correctly account for a * fallocated page arriving here is now to initialize it and write it. + * + * That's okay for a page already fallocated earlier, but if we have + * not yet completed the fallocation, then (a) we want to keep track + * of this page in case we have to undo it, and (b) it may not be a + * good idea to continue anyway, once we're pushing into swap. So + * reactivate the page, and let shmem_fallocate() quit when too many. */ if (!PageUptodate(page)) { + if (inode->i_private) { + struct shmem_falloc *shmem_falloc; + spin_lock(&inode->i_lock); + shmem_falloc = inode->i_private; + if (shmem_falloc && + index >= shmem_falloc->start && + index < shmem_falloc->next) + shmem_falloc->nr_unswapped++; + else + shmem_falloc = NULL; + spin_unlock(&inode->i_lock); + if (shmem_falloc) + goto redirty; + } clear_highpage(page); flush_dcache_page(page); SetPageUptodate(page); @@ -1647,6 +1679,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, { struct inode *inode = file->f_path.dentry->d_inode; struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); + struct shmem_falloc shmem_falloc; pgoff_t start, index, end; int error; @@ -1679,6 +1712,14 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, goto out; } + shmem_falloc.start = start; + shmem_falloc.next = start; + shmem_falloc.nr_falloced = 0; + shmem_falloc.nr_unswapped = 0; + spin_lock(&inode->i_lock); + inode->i_private = &shmem_falloc; + spin_unlock(&inode->i_lock); + for (index = start; index < end; index++) { struct page *page; @@ -1688,6 +1729,8 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, */ if (signal_pending(current)) error = -EINTR; + else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced) + error = -ENOMEM; else error = shmem_getpage(inode, index, &page, SGP_FALLOC, NULL); @@ -1696,10 +1739,18 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, shmem_undo_range(inode, (loff_t)start << PAGE_CACHE_SHIFT, (loff_t)index << PAGE_CACHE_SHIFT, true); - goto ctime; + goto undone; } /* + * Inform shmem_writepage() how far we have reached. + * No need for lock or barrier: we have the page lock. + */ + shmem_falloc.next++; + if (!PageUptodate(page)) + shmem_falloc.nr_falloced++; + + /* * If !PageUptodate, leave it that way so that freeable pages * can be recognized if we need to rollback on error later. * But set_page_dirty so that memory pressure will swap rather @@ -1714,8 +1765,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size) i_size_write(inode, offset + len); -ctime: inode->i_ctime = CURRENT_TIME; +undone: + spin_lock(&inode->i_lock); + inode->i_private = NULL; + spin_unlock(&inode->i_lock); out: mutex_unlock(&inode->i_mutex); return error; |