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usb: gadget: mass_storage: fail fsg_store_file() early if colud not open file 

Currently, when a new value is stored to the “file” sysfs entry,
fsg_store_file() will release existing backing file and only then attempt to
open a new one.  If that fails, no new backing file is open.

This commit changes the fsg_lun_open() so that it closes existing backing file
only after the new backing file has been successfully opened.  With that
change, fsg_store_file() may use it to perform an atomic open operation with
guarantee that logical unit will either point to the new backing file or still
to the old one.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu
Signed-off-by: Felipe Balbi <balbi@ti.com>
This commit is contained in:
Michal Nazarewicz 2012-06-18 14:37:20 +02:00 committed by Felipe Balbi
parent f87cabf4d5
commit d6e16a8957
1 changed files with 29 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
drivers/usb/gadget/storage_common.c
View File

@ -617,6 +617,16 @@ static struct usb_gadget_strings fsg_stringtab = {
* the caller must own fsg->filesem for writing.
*/
static void fsg_lun_close(struct fsg_lun *curlun)
{
if (curlun->filp) {
LDBG(curlun, "close backing file\n");
fput(curlun->filp);
curlun->filp = NULL;
}
}
static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
{
int ro;
@ -626,6 +636,8 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
loff_t size;
loff_t num_sectors;
loff_t min_sectors;
unsigned int blkbits;
unsigned int blksize;
/* R/W if we can, R/O if we must */
ro = curlun->initially_ro;
@ -670,17 +682,17 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
}
if (curlun->cdrom) {
curlun->blksize = 2048;
curlun->blkbits = 11;
blksize = 2048;
blkbits = 11;
} else if (inode->i_bdev) {
curlun->blksize = bdev_logical_block_size(inode->i_bdev);
curlun->blkbits = blksize_bits(curlun->blksize);
blksize = bdev_logical_block_size(inode->i_bdev);
blkbits = blksize_bits(blksize);
} else {
curlun->blksize = 512;
curlun->blkbits = 9;
blksize = 512;
blkbits = 9;
}
num_sectors = size >> curlun->blkbits; /* File size in logic-block-size blocks */
num_sectors = size >> blkbits; /* File size in logic-block-size blocks */
min_sectors = 1;
if (curlun->cdrom) {
min_sectors = 300; /* Smallest track is 300 frames */
@ -697,7 +709,12 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
goto out;
}
if (fsg_lun_is_open(curlun))
fsg_lun_close(curlun);
get_file(filp);
curlun->blksize = blksize;
curlun->blkbits = blkbits;
curlun->ro = ro;
curlun->filp = filp;
curlun->file_length = size;
@ -711,16 +728,6 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
}
static void fsg_lun_close(struct fsg_lun *curlun)
{
if (curlun->filp) {
LDBG(curlun, "close backing file\n");
fput(curlun->filp);
curlun->filp = NULL;
}
}
/*-------------------------------------------------------------------------*/
/*
@ -871,19 +878,18 @@ static ssize_t fsg_store_file(struct device *dev, struct device_attribute *attr,
if (count > 0 && buf[count-1] == '\n')
((char *) buf)[count-1] = 0; /* Ugh! */
/* Eject current medium */
down_write(filesem);
if (fsg_lun_is_open(curlun)) {
fsg_lun_close(curlun);
curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
}
/* Load new medium */
down_write(filesem);
if (count > 0 && buf[0]) {
/* fsg_lun_open() will close existing file if any. */
rc = fsg_lun_open(curlun, buf);
if (rc == 0)
curlun->unit_attention_data =
SS_NOT_READY_TO_READY_TRANSITION;
} else if (fsg_lun_is_open(curlun)) {
fsg_lun_close(curlun);
curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
}
up_write(filesem);
return (rc < 0 ? rc : count);