[PATCH 3.8 113/133] don't bother with {get,put}_write_access() on non-regular files

From: Kamal Mostafa
Date: Tue Apr 22 2014 - 16:22:01 EST


3.8.13.22 -stable review patch. If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit d23142c6271c499d913d0d5e668b5a4eb6dafcb0 upstream.

it's pointless and actually leads to wrong behaviour in at least one
moderately convoluted case (pipe(), close one end, try to get to
another via /proc/*/fd and run into ETXTBUSY).

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
fs/file_table.c | 4 ++--
fs/open.c | 26 +++++++-------------------
2 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index de9e965..ff2d2e8 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -211,10 +211,10 @@ static void drop_file_write_access(struct file *file)
struct dentry *dentry = file->f_path.dentry;
struct inode *inode = dentry->d_inode;

- put_write_access(inode);
-
if (special_file(inode->i_mode))
return;
+
+ put_write_access(inode);
if (file_check_writeable(file) != 0)
return;
__mnt_drop_write(mnt);
diff --git a/fs/open.c b/fs/open.c
index 9b33c0c..4a02b5a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -641,23 +641,12 @@ out:
static inline int __get_file_write_access(struct inode *inode,
struct vfsmount *mnt)
{
- int error;
- error = get_write_access(inode);
+ int error = get_write_access(inode);
if (error)
return error;
- /*
- * Do not take mount writer counts on
- * special files since no writes to
- * the mount itself will occur.
- */
- if (!special_file(inode->i_mode)) {
- /*
- * Balanced in __fput()
- */
- error = __mnt_want_write(mnt);
- if (error)
- put_write_access(inode);
- }
+ error = __mnt_want_write(mnt);
+ if (error)
+ put_write_access(inode);
return error;
}

@@ -690,12 +679,11 @@ static int do_dentry_open(struct file *f,

path_get(&f->f_path);
inode = f->f_path.dentry->d_inode;
- if (f->f_mode & FMODE_WRITE) {
+ if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
error = __get_file_write_access(inode, f->f_path.mnt);
if (error)
goto cleanup_file;
- if (!special_file(inode->i_mode))
- file_take_write(f);
+ file_take_write(f);
}

f->f_mapping = inode->i_mapping;
@@ -737,7 +725,6 @@ cleanup_all:
fops_put(f->f_op);
file_sb_list_del(f);
if (f->f_mode & FMODE_WRITE) {
- put_write_access(inode);
if (!special_file(inode->i_mode)) {
/*
* We don't consider this a real
@@ -745,6 +732,7 @@ cleanup_all:
* because it all happenend right
* here, so just reset the state.
*/
+ put_write_access(inode);
file_reset_write(f);
__mnt_drop_write(f->f_path.mnt);
}
--
1.9.1

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