From 2e0e26c76a35de8f8bec6b2b917518cfeb52888a Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 4 Feb 2008 22:28:53 -0800 Subject: tmpfs: open a window in shmem_unuse_inode There are a couple of reasons (patches follow) why it would be good to open a window for sleep in shmem_unuse_inode, between its search for a matching swap entry, and its handling of the entry found. shmem_unuse_inode must then use igrab to hold the inode against deletion in that window, and its corresponding iput might result in deletion: so it had better unlock_page before the iput, and might as well release the page too. Nor is there any need to hold on to shmem_swaplist_mutex once we know we'll leave the loop. So this unwinding moves from try_to_unuse and shmem_unuse into shmem_unuse_inode, in the case when it finds a match. Let try_to_unuse break on error in the shmem_unuse case, as it does in the unuse_mm case: though at this point in the series, no error to break on. Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/shmem.c | 57 +++++++++++++++++++++++++++++++++++---------------------- 1 file changed, 35 insertions(+), 22 deletions(-) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index 2e03d6031c2..a0126c43710 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -838,10 +838,8 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, s if (size > SHMEM_NR_DIRECT) size = SHMEM_NR_DIRECT; offset = shmem_find_swp(entry, ptr, ptr+size); - if (offset >= 0) { - shmem_swp_balance_unmap(); + if (offset >= 0) goto found; - } if (!info->i_indirect) goto lost2; @@ -879,11 +877,11 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, s if (size > ENTRIES_PER_PAGE) size = ENTRIES_PER_PAGE; offset = shmem_find_swp(entry, ptr, ptr+size); + shmem_swp_unmap(ptr); if (offset >= 0) { shmem_dir_unmap(dir); goto found; } - shmem_swp_unmap(ptr); } } lost1: @@ -893,10 +891,25 @@ lost2: return 0; found: idx += offset; - inode = &info->vfs_inode; - error = add_to_page_cache(page, inode->i_mapping, idx, GFP_ATOMIC); + inode = igrab(&info->vfs_inode); + spin_unlock(&info->lock); + + /* move head to start search for next from here */ + list_move_tail(&shmem_swaplist, &info->swaplist); + mutex_unlock(&shmem_swaplist_mutex); + + error = 1; + if (!inode) + goto out; + + spin_lock(&info->lock); + ptr = shmem_swp_entry(info, idx, NULL); + if (ptr && ptr->val == entry.val) + error = add_to_page_cache(page, inode->i_mapping, + idx, GFP_ATOMIC); if (error == -EEXIST) { struct page *filepage = find_get_page(inode->i_mapping, idx); + error = 1; if (filepage) { /* * There might be a more uptodate page coming down @@ -911,16 +924,18 @@ found: delete_from_swap_cache(page); set_page_dirty(page); info->flags |= SHMEM_PAGEIN; - shmem_swp_set(info, ptr + offset, 0); + shmem_swp_set(info, ptr, 0); + swap_free(entry); + error = 1; /* not an error, but entry was found */ } - shmem_swp_unmap(ptr); + if (ptr) + shmem_swp_unmap(ptr); spin_unlock(&info->lock); - /* - * Decrement swap count even when the entry is left behind: - * try_to_unuse will skip over mms, then reincrement count. - */ - swap_free(entry); - return 1; +out: + unlock_page(page); + page_cache_release(page); + iput(inode); /* allows for NULL */ + return error; } /* @@ -935,18 +950,16 @@ int shmem_unuse(swp_entry_t entry, struct page *page) mutex_lock(&shmem_swaplist_mutex); list_for_each_safe(p, next, &shmem_swaplist) { info = list_entry(p, struct shmem_inode_info, swaplist); - if (!info->swapped) + if (info->swapped) + found = shmem_unuse_inode(info, entry, page); + else list_del_init(&info->swaplist); - else if (shmem_unuse_inode(info, entry, page)) { - /* move head to start search for next from here */ - list_move_tail(&shmem_swaplist, &info->swaplist); - found = 1; - break; - } cond_resched(); + if (found) + goto out; } mutex_unlock(&shmem_swaplist_mutex); - return found; +out: return found; /* 0 or 1 or -ENOMEM */ } /* -- cgit v1.2.3