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authorHugh Dickins <hugh@veritas.com>2008-02-04 22:28:53 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-05 09:44:15 -0800
commit2e0e26c76a35de8f8bec6b2b917518cfeb52888a (patch)
tree1357781bfe035c2401c65b2d0203385a47516bf5 /mm/shmem.c
parentcb5f7b9a47963d9238398cd0c2676473e3c6896d (diff)
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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 <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
-rw-r--r--mm/shmem.c57
1 files changed, 35 insertions, 22 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 2e03d6031c24..a0126c437105 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 */
}
/*