From: Hugh Dickins In the new aops, write_begin is supposed to return the page locked: though I've seen no ill effects, that's been overlooked in the case of shmem_write_begin, and should be fixed. Then shmem_write_end must unlock the page: do so _after_ updating i_size, as we found to be important in other filesystems (though since shmem pages don't go the usual writeback route, they never suffered from that corruption). For shmem_write_begin to return the page locked, we need shmem_getpage to return the page locked in SGP_WRITE case as well as SGP_CACHE case: let's simplify the interface and return it locked even when SGP_READ. Signed-off-by: Hugh Dickins Acked-by: Rik van Riel Cc: Nick Piggin Signed-off-by: Andrew Morton --- mm/shmem.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff -puN mm/shmem.c~shmem_getpage-return-page-locked mm/shmem.c --- a/mm/shmem.c~shmem_getpage-return-page-locked +++ a/mm/shmem.c @@ -729,6 +729,8 @@ static int shmem_notify_change(struct de (void) shmem_getpage(inode, attr->ia_size>>PAGE_CACHE_SHIFT, &page, SGP_READ, NULL); + if (page) + unlock_page(page); } /* * Reset SHMEM_PAGEIN flag so that shmem_truncate can @@ -1286,12 +1288,7 @@ repeat: SetPageUptodate(filepage); } done: - if (*pagep != filepage) { - *pagep = filepage; - if (sgp != SGP_CACHE) - unlock_page(filepage); - - } + *pagep = filepage; return 0; failed: @@ -1469,12 +1466,13 @@ shmem_write_end(struct file *file, struc { struct inode *inode = mapping->host; + if (pos + copied > inode->i_size) + i_size_write(inode, pos + copied); + + unlock_page(page); set_page_dirty(page); page_cache_release(page); - if (pos+copied > inode->i_size) - i_size_write(inode, pos+copied); - return copied; } @@ -1529,6 +1527,7 @@ shmem_file_write(struct file *file, cons if (err) break; + unlock_page(page); left = bytes; if (PageHighMem(page)) { volatile unsigned char dummy; @@ -1610,6 +1609,8 @@ static void do_shmem_file_read(struct fi desc->error = 0; break; } + if (page) + unlock_page(page); /* * We must evaluate after, since reads (unlike writes) @@ -1899,6 +1900,7 @@ static int shmem_symlink(struct inode *d iput(inode); return error; } + unlock_page(page); inode->i_op = &shmem_symlink_inode_operations; kaddr = kmap_atomic(page, KM_USER0); memcpy(kaddr, symname, len); @@ -1926,6 +1928,8 @@ static void *shmem_follow_link(struct de struct page *page = NULL; int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL); nd_set_link(nd, res ? ERR_PTR(res) : kmap(page)); + if (page) + unlock_page(page); return page; } _