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IMFS: Lock the file system during directory reads

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Other threads may add or remove directory entries during a read of the
directory.  Use the file system instance lock for protection.
This commit is contained in:
Sebastian Huber
2012-02-21 17:21:05 +01:00
parent e00cca9b74
commit 316507ab91
1 changed files with 15 additions and 21 deletions
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36
cpukit/libfs/src/imfs/imfs_directory.c
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@@ -81,34 +81,29 @@ ssize_t imfs_dir_read(
int last_entry;
struct dirent tmp_dirent;
rtems_filesystem_instance_lock( &iop->pathinfo );
the_jnode = (IMFS_jnode_t *)iop->pathinfo.node_access;
the_chain = &the_jnode->info.directory.Entries;
if ( rtems_chain_is_empty( the_chain ) )
return 0;
/* Move to the first of the desired directory entries */
the_node = rtems_chain_first( the_chain );
bytes_transferred = 0;
first_entry = iop->offset;
/* protect against using sizes that are not exact multiples of the */
/* -dirent- size. These could result in unexpected results */
last_entry = first_entry + (count/sizeof(struct dirent)) * sizeof(struct dirent);
last_entry = first_entry
+ (count / sizeof( struct dirent )) * sizeof( struct dirent );
/* The directory was not empty so try to move to the desired entry in chain*/
for (
current_entry = 0;
current_entry < last_entry;
current_entry = current_entry + sizeof(struct dirent) ){
if ( rtems_chain_is_tail( the_chain, the_node ) ){
/* We hit the tail of the chain while trying to move to the first */
/* entry in the read */
return bytes_transferred; /* Indicate that there are no more */
/* entries to return */
}
current_entry = 0,
the_node = rtems_chain_first( the_chain );
current_entry < last_entry
&& !rtems_chain_is_tail( the_chain, the_node );
current_entry += sizeof( struct dirent ),
the_node = rtems_chain_next( the_node )
) {
if( current_entry >= first_entry ) {
/* Move the entry to the return buffer */
tmp_dirent.d_off = current_entry;
@@ -122,14 +117,13 @@ ssize_t imfs_dir_read(
(void *)&tmp_dirent,
sizeof( struct dirent )
);
iop->offset = iop->offset + sizeof(struct dirent);
bytes_transferred = bytes_transferred + sizeof( struct dirent );
iop->offset += sizeof( struct dirent );
bytes_transferred += sizeof( struct dirent );
}
the_node = the_node->next;
}
/* Success */
rtems_filesystem_instance_unlock( &iop->pathinfo );
return bytes_transferred;
}