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Commit d6e16a89 authored by Michal Nazarewicz's avatar Michal Nazarewicz Committed by Felipe Balbi
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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: default avatarMichal Nazarewicz <mina86@mina86.com>
Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarFelipe Balbi <balbi@ti.com>
parent f87cabf4

drivers/usb/gadget/storage_common.c

+29 −23
Original line number Diff line number Diff line
@@ -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);